S8 Roll Bar Mod, Part 1--rear: backgrounder & step by step of how to really do it (non-Bentley!)
02-23-2008, 09:57 PM
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S8 Roll Bar Mod, Part 1--rear: backgrounder & step by step of how to really do it (non-Bentley!)
I have been threatening to get this mod done. Today was part 1, the rear bar. I intend this mod as well as this post as a work in process. I will be driving it with just the rear installed for a while before moving on to the front, to report my impressions separately. While it is fresh, I will write up the technique and tips here, as well as all the bar details I know. Yeah, most of you are probably armchair types, but as the car ages someone will pick this up hopefully. Or maybe you know a tuner friend or wrench turner or something. Given there are no electronics here--just good old wrenching--the chances of screwing something up big time are really low, as long as you use basic shop safety.
I went for the rear bar first because from my C5 4.2 (the flared A6) experience--a car that doesn't weigh that much less than an A8 because of its steel body--modifying the rear bar has the largest effect. It stiffens up the suspension more overall and has more effect on reducing understeer, all assuming a reasonable front bar to start of course. My C5 experience is stiffening the bars was something similar to going from stock struts to HD struts (but not full-on sport struts), or maybe going up one inch in wheel size and down one aspect ratio step.
The S8 part number: 3D0-511-407B. When I bought it (from Clair) at the end of January 2008, dealer list was just under $200. With a discount, it cost a bit less than the rear sport bar for the C5 with the necessary separate parts that bar required. Good bet Audi parts prices are headed up though with the fall of the U.S. dollar. It is a single part number for the S8 bar (same in the front too), which includes the two bushings already on the bar, as well as the two aluminum bushing clamps that bolt to the rear subframe area. Picture 4 below shows you the bushing area of the old bar before removal. Oh yeah, there were like about none of the S8 bars in the country when I ordered them, so expect it may be a while--not often a rear bar (tucked way up high too) in a low volume car would need replacing absent a big accident.
The specs: it was apparently referred to in the parts listing as a 20mm bar. I measured it at 20.1-20.2 mm in diameter. Appears to be a solid bar. The front bar is clearly tubular for reference.
The car: I have a W12. Vehicle weight can matter with bars, and different bars are often spec'ed across engines as weight and expected harder driving go up. A W12 always makes it a long body (in the U.S.) while the S8 is always a short body worldwide. Audi specs the W12 motor weight at 245kg (540 lbs), vs. 220 kg. (485 lbs.) for the S8. The Euro spec for the W12 where a short body exists says the added body length adds 35kg (77 lbs). A W12 is loaded of course so it is the heaviest among D3's. But, the S8 is also heavily equipped--in more ways than one... Recent Audi spec'ed U.S. curb weight is 4729 lbs (2145 kg) on a W12, and 4586 lbs (2080 kg) on an S8, or 143 lbs heavier overall, which is close to the combined motor and body weight increments. To my mind, not a big percentage weight difference between the two and actually pretty evenly distributed front and back. For reference an A8L and an A8 (short) are on the order of 300 lbs less for a given body length to either the W12 (in long) or the S8 (in short). I dredge all this up because the heavier the car, the more there is to control with a roll bar.
The baseline bar: The bar I pulled off (again, in a W12) was 4E0 511 407J. Its measured diameter was approximately 19.2mm, or only about 1 mm less than the S8 bar. Read on though, you will find it was already a "sport suspension" bar for D3's. Note just that 1 mm difference is a bit over a 10% increase in (solid) cross sectional area, so it is still likely meaningful in terms of stiffness. The part number as well as manufacture date was clearly visible in white printing along the bottom center area of the bar, basically in between the two sides of the exhaust. Makes it handy to check your installed part number. Unfortunately, the painted number on the new bar wasn't so clear, though it was well tagged to start.
The new and old bars, with the new bar label; note old bar part number and manufacture date is clearly visible:
<img src="http://pictureposter.audiworld.com/26081/img_3020.jpg">
Picture 1
More on stock bars: So mine was a 4E0 511 407J in a W12 as you can see in the picture just above. Turns out my parts listing says that is the "sport suspension" bar for any 4.2 A8/A8L. Clair also mentioned the Audi dealer parts system said it was the bar for cars with the BVJ motor, which is the FSI 4.2. Maybe they went to a stiffer bar automatically at that point. By the way in writing this up, I noticed the 2008 specs add 30 or 40 pounds to the curb weight of a 4.2 over prior years. Could be some of the new features and sound insulation, but I bet maybe they just caught the spec up in part for what I'm guessing may be a bit heavier 4.2 motor with FSI). Note there is no such thing in the US as a "sport suspension" W12 like there is for a 4.2. You might guess they would go for plush, though this bar use that I confirmed in the field contraindicates that. I am guessing when I pull the front bar off, it will also be equivalent to a sport suspension version on a 4.2. The air shocks are different in a sports suspension car too, but so far I haven't found that number on the car. Using the heavier bar does make some sense just given the extra car weight.
Also for reference, my A8 parts listing says the non-sport bar part number is 4E0 511 407D. I am hoping someone can climb under their non-sport 4.2 A8 or A8L at some point and confirm that, or do so if they replace their bar. I don't have a diameter measurement on that either if someone cares to contribute it. Remember, if you have a stock (non sport) bar, doing this with the S8 bar is taking you up "two notches." You could consider using just the sport bar instead. But my advice would be probably go all the way to the S8 bars if you want it stiffen it up in general. Stiffer bars do have some effect on the overall suspension and not just cornering, even if you leave the air shocks alone (which on an A8 with the cost and electronics, coupled with the MMI adjustability to start, is what I would do almost for sure).
How do I know which suspension I am supposed to have?: It's on the build sticker actually, which is copied in your service manual if it is all up to snuff, or if not on the sticker in the wheel well area in the trunk. It is the last code on the far right hand side of the second line of codes under "options." 1BK is a standard suspension (what mine says, but W12 style if you will), 2MA is a sport suspension, 2MB is an S8 suspension.
Getting ready for the install: Here I have to say Bentley was pretty worthless. It said I had to dismantle the whole rear exhaust, take off both wheels (not good for roll bars when trying to keep suspension loaded; more below) and also detach the rear air shocks from the suspension. Didn't matter for a W12 or any other D3--toward the rear what is under there is very similar, just somewhat bigger. No way was I headed this overblown direction (took Bentley only three lines to summarily say disassemble half the rear of the car!), just wasn't going to happen. From my C5 experience I knew you could typically snake them out with some levering and persuasion. But this bad boy was definitely meatier in the rear than a C5 and I could see those parking brake motors and lots of suspension bolt up points were looming.
Tools: as it rolled along, it was basically the normal metric sockets, various extensions, a torque wrench. A starred 12 point Allen type tool is needed to get the roll bar clamps off the body--mine is unmarked, but I think they would call it 10mm. You need to use a 3/8" drive or regular wrenches to get at the bar end bolt--it is close to the rear caliper parking brake motors. I usually used ½" drives otherwise. Also some Locktite to put on all the bolts, assuming you aren't going to bother replacing them. Definitely needed a drop light or something similar to see when doing some steps.
Manpower: it's a one person job straight up, unless you need help with the beer or a tool and parts jockey, and/or someone to talk to. Unlike the C5 where you have to wrestle the exhaust and one guy pulling and one guy working the bar in or out is best, with the approach I arrived at for the D3 it was just me all the way through without breaking a sweat.
A step-by-step breakdown of my technique. This is the home DIY version without mega pro tools. It differs radically from Bentley actually in the key approach--bar comes out sideways, not straight down and not at an odd angle by brute force like the C5--which is why I detail it here:
1. Drive rear wheels up on ramps (or do it on a four corner lift where the wheels still carry the weight). From experience with rollbars you typically want the suspension loaded up when you bolt the rollbar up. Helps avoid groaning noises too. Turned out I found out later this was very important for the trailing arm connection too. Put car in jack mode via MMI (more on why that later...).
Oh s%$#, Houston we have a problem...
<img src="http://pictureposter.audiworld.com/26081/img_3007.jpg">
Picture 2
2. Observe from underneath that the rear trailing suspension link on both sides is dead nuts in the way to possibly get the bar out. (The "oh s%$#" moment for me that caused me to pull out Bentley). The picture above is from directly below the driver's side rear trailing link. Up is toward the rear of the car. The roll bar is the black tubular part in the lower right middle that then heads behind the trailing link. Okay, so attack it. ABSOLUTELY mark the position of the mounting bolts for the inner trailing link bolt up point. Mark BOTH the front and rear with a Sharpie. Mark between the eccentric washer and the rear subframe it bolts to on both sides with at least two distinct perpendicular lines. This bolt controls rear toe, so if you fail to do this, you will be screwed and end up needing a rear alignment. Do it, or be sorry when you are forced to approximate! Once marking it, remove the bolt--18mm sockets on both sides. Without much force, you can pull the arm out of the subframe area and well out of the way. Do not remove the outer end--it would be a waste of time and no reason to at all.
Note in the next picture taken on the driver's side somewhat to the rear and below the suspension and again showing the obstruction caused by the trailing link, that I marked the washer and surrounding subframe. It is in the upper right. Nothing fancy. The antiroll bar is in the upper left part of the picture just at the shadow transition line.
<img src="http://pictureposter.audiworld.com/26081/img_3008_copy.jpg">
Picture 3
Now, with the link cleared away, notice below what a straight shot things are now to get at. The next picture was taken from directly below, also on the driver's side. You can see the bushing clamp bolt up point clearly at the aluminum subframe. Up is toward the back of the car (note part of muffler), down is to the front (note CV axle--curvature is close-in lens distortion not my car!):
<img src="http://pictureposter.audiworld.com/26081/img_3009.jpg">
Picture 4
3. Proceed to unbolt bar. Both the clamps that bolt to the rear subframe as well as at the ends where it bolts to the links. Here is where you need the 12 point allen head tool (apparently 10mm size; you can see the heads with the slight greenish tinge in the picture above), and clearance is tight on the sides for the end bolts because of the parking brake motor units on the back of the rear calipers. Still straight forward to do with a 3/8" socket drive (16mm). Doesn't seem to matter what order you do it in.
4. Pull the aluminum rubber bushing clamps off of the bushings; they interfere with trying to get the bar out otherwise. Notice in the picture above they actually extend through a punchout in part of the subframe that is sheet stock welded on.
5. Take one wheel off. Yup, here is where it goes totally off script and Bentley (and probably Audi for their tech training) completely missed the boat. There was no way I was going to drop the exhaust and all that stuff, especially in supersized W12 form. I tried snaking the bar out with it unbolted and the trailing links out of the way--the old C5 brute force idea--but there was no way it could have gone. I would have sawed it easily, but that doesn't help the install. But wait, I noticed it looked like a straight shot out the side if I took off a wheel. For anyone (probably not a regular D3 owner...) who ever took a steering rack out of, say a C3, it would be familiar. Seemed like removing either wheel would work. Based on how I had the car in my garage, I chose the rear right side one. I actually put the car in jack mode here, but I think you could do it back at step 1, unless it changes the suspension geometry a lot for the trailing link bolt removal at step 2. I doubt it does. Since I had it on ramps already, I used a floor jack (with a rubber pad) at the rear jack point and took the right rear of the car up another few inches (left side still on the ramp). I unbolted the wheel and put it well aside.
6. Insert jack stand. You need to get under the car later to get the new bar in. Safety first. The car was so high and a D3 underside is so smooth that it wasn't clear how to use a jack stand at first. Eventually I put my now freed up ramp base (mine are the metal two part type with a flat top) under the rear differential area and then jack standed from there to just under the differential case. It was well positioned and sturdy. Note if you use a drive-on four post type lift, it might get tricky here since you would now need to jack up one wheel and then get it off. Regardless, now remove the jacked up wheel.
7. With the wheel off, it was a cinch to pull the bar out. Much easier than threading it out on a C5 actually. Basically I simply rotated it by 180 degrees to the where the bent ends were now well clear of the bolt up points and rear rotor splash shield. Remember W12 brakes are bigger too, so if I could get it, any D3 would be as easy or easier. Pulled out sideways with a few twists and minor tugs. No major forcing or levering needed. A nice feeling, since now I knew the new one was definitely going in without a big hassle.
The money shot (with some near field blurring). The bar is rotated 180 degrees now. You can see the bolt hole at the near end toward the lower left. The bright somewhat fuzzy silver object with the half circle cutout is the right rear brake caliper with the wheel now off. Dropping straight down from what seems like the lower left of the brake caliper (actually maybe six inches behind it) is the near side trailing link which was unbolted and left out of the way. The reddish looking thing you see running vertically in the lower center is the same trailing link over on the far side (just distorted with the zoom effect and the lighting). In the upper middle and partially in the shadows you see the bar snaking back toward the far side. (The more pronounced bent pipe that seems to start behind the exhaust pipe in the center of the picture is actually part of the fuel vapor recovery system, not the roll bar.) That little white triangle in the upper middle is actually light all the way from the far side from gaps in the wheel spokes, thus showing how it is now a clear passage left to right to remove and reinsert the bar:
<img src="http://pictureposter.audiworld.com/26081/img_3018.jpg">
Picture 5
8. Start reassembly. Prepare new bar by removing the bolt up clamps that are likely on there from the dealer, plus all the paper label stuff. Clamps need to stay off until you bolt it up. They get in the way of threading it back in for starters. Remember visually which is the front and which is the rear of the clamp shell--the two shapes vary from front to back of the shell. Maybe mark an arrow with a Sharpie.
9. Thread bar back in like you pulled it out. Likely you will need to go under to get it unsnagged as you snake the "front" bent end of the bar past the exhaust pipes. But again, it's not a tough force fit. Here's where you better have that jack stand (or two) in place for sure, especially given the wheel is off completely.
9. Once the bar is in the general area it will end up, get underneath and get it closer to the final position.
10. At this point I started looking at the rear trailing links again. Good thing I did as it turned out. Basically with the car jacked up, and the rear suspension now unloaded this link will not bolt back in without at least undoing the other end, and probably then hammering on things. But wait, don't do that. The fix is easy.
11. Reinstall and torque wheel. Replace ramp (if you are using them). Remove jack stand. Lower car back down so rear suspension is fully weight bearing (but still up high on the ramps).
12. Swing the rear trailing links back into position, working the long rubber bushing through which the bolt will pass (visible in Picture 2 in the lower center) back up into the subframe area where it fits--it is now a straightforward fit that wasn't possible when the wheel was off and the suspension unloaded).
13. Now bolt back up the rear trailing links. Here is where you really need those alignment marks with the Sharpie from earlier. Note the bolts have slits perpendicular to the threads. Those need to face upward, as I found out after a quick false start. Start on either side. Put the bolt in from the front side and the eccentric washer on the rear side, Sharpie marks facing out (ask me how I learned that...). Apply a bit of Locktite. Then bolt it up to where it is just close to snug. Do ALL the tightening on the nut side only--that slit fits into the washer that has a tooth in the center hole to match and you don't want to force it. When you are close to snug, then turn the bolt on the head side (from the front of the car that is) just marginally WITHOUT holding the nut with any wrench. That causes the eccentric washer to move on the nut side because of the tooth in the washer that is in that bolt groove. Voila, you are now a rear alignment pro and setting the rear toe alignment back to where it started. Now line up your Sharpie marks on the rear eccentric washer exactly (or start over when you found the washer went in backwards and you don't see the marks...) by turning the bolt head from the front with the socket drive. Once you are there, snug up the nut a bit more so things won't move easily. Now, really nail the adjustment from the bolt head side too. If you look the Sharpie marks on that side won't quite be right. It is the minor play in the slot of the bolt transferring through to the back side washer. Simply turn the bolt head side back a bit the other way without touching the nut side. Now those marks should line up dead nuts too, and you should find the rear side unchanged. Assuming all is in order, now tighten the rear nut side down to torque (95nm).
14. Repeat #13 for other side trailing link.
15. Now proceed to get the bar bolted back up. Start by working those aluminum bushing shells onto the rubber. Note they bolt to the subframe only one way. Follow your marks from #8 (or if you laid them out as you removed them, how they were put down back in step 6). Or, if you just forgot or kicked them, just look for the outlines of the old ones on the rear subframe and match them up. Now work those bushing shells up toward their bolt up points. I stopped here without bolting them in to be sure all would work at the ends in the next step.
16. With the bushing clamps now on the (still loose) bar, work the ends of the bar into the ends of the suspension coupling links they bolt to--the dumbbell shaped things. The first side is easy. Just get a bolt (with a bit of Locktite) in there a few turns. For the other side, you need to force the bar back toward the side you first bolted loosely while also pushing the other coupling link dumbbell shaped thing outward to slide the bar end inside of it. It has a bit of a lip that holds it all together when lined up. Again, moderate force by hand was all it took. Just fit the bolt in a few turns.
17. Now with the ends loosely in place, bolt the bar up to the subframe. Those bushing clamp caps are a bit fussy getting into the punched out part of the subframe sheet plate aluminum, but again it should go by hand with no levering. Once generally in the area, apply Locktite to those 12 point bolts and work them all in loosely ( a few turns), doing both sides. I used the 12 point tool on a socket extension with no ratchet to turn them in, since the bolt heads are round, not six sided, and are hard to turn with just your fingers.
18. Now bolt the bar up tight. Doesn't seem to matter in terms of fit which part you do first. I did the ends first so the bushings would be bolted in most at their "rest" final position to minimize squeaking downstream. Torque the bar end bolts to 65nm. I did not have a 3/8" ratchet type torque wrench (there is no way to fit a ½" drive in there with the brake caliper in place, so I went with the feel o meter--decent pressure with a 3/8" drive. The swivel head type was best since the access to the bolt is a bit off angle and there isn't enough room to fit in a swiveling joint type socket extension. Then I bolted up the bushing clamp shells--gradually going back and forth among the bolts to ease everything in and then tight once I got to metal to metal contact of clamp shell to the subframe. Now torque these (25 nm). Low enough torque I had to use a 3/8" type torque wrench to set it low enough. Mine doesn't ratchet but that was fine here since you access them in a straight upward direction.
19. Okay if I remembered all the steps, it's about done. Of course if you have a W12, here is where you take a detour and unplug the solenoids on each side for those low speed exhaust valves that close off 2/3's of the flow at low speeds, but that's another posting...
20. Remove all tools. Get in car (in clean clothes...), take out of jack mode (it does it automatically if you forget), and drive it off the ramps carefully.
There you go, 20 logical steps later, all with pretty normal equipment and without first disassembling half your car too.
Front's are much easier from experience. Half a dozen no brainer type steps from the C5 experience and from what I have seen under the D3 too. That will be a future installment.
Total elapsed time, maybe 5 hours. But at least an hour and a half of that was checking out the exhaust and cleaning stuff up around the car. And I was doing lots of other household stuff off and on, and I explained to my teenage son how sway bars work. Now knowing Bentley is worthless and doing it this way, I would say about two hours + start to finish for the rear with the right tools nearby.
Road test results/comparison to follow.
I went for the rear bar first because from my C5 4.2 (the flared A6) experience--a car that doesn't weigh that much less than an A8 because of its steel body--modifying the rear bar has the largest effect. It stiffens up the suspension more overall and has more effect on reducing understeer, all assuming a reasonable front bar to start of course. My C5 experience is stiffening the bars was something similar to going from stock struts to HD struts (but not full-on sport struts), or maybe going up one inch in wheel size and down one aspect ratio step.
The S8 part number: 3D0-511-407B. When I bought it (from Clair) at the end of January 2008, dealer list was just under $200. With a discount, it cost a bit less than the rear sport bar for the C5 with the necessary separate parts that bar required. Good bet Audi parts prices are headed up though with the fall of the U.S. dollar. It is a single part number for the S8 bar (same in the front too), which includes the two bushings already on the bar, as well as the two aluminum bushing clamps that bolt to the rear subframe area. Picture 4 below shows you the bushing area of the old bar before removal. Oh yeah, there were like about none of the S8 bars in the country when I ordered them, so expect it may be a while--not often a rear bar (tucked way up high too) in a low volume car would need replacing absent a big accident.
The specs: it was apparently referred to in the parts listing as a 20mm bar. I measured it at 20.1-20.2 mm in diameter. Appears to be a solid bar. The front bar is clearly tubular for reference.
The car: I have a W12. Vehicle weight can matter with bars, and different bars are often spec'ed across engines as weight and expected harder driving go up. A W12 always makes it a long body (in the U.S.) while the S8 is always a short body worldwide. Audi specs the W12 motor weight at 245kg (540 lbs), vs. 220 kg. (485 lbs.) for the S8. The Euro spec for the W12 where a short body exists says the added body length adds 35kg (77 lbs). A W12 is loaded of course so it is the heaviest among D3's. But, the S8 is also heavily equipped--in more ways than one... Recent Audi spec'ed U.S. curb weight is 4729 lbs (2145 kg) on a W12, and 4586 lbs (2080 kg) on an S8, or 143 lbs heavier overall, which is close to the combined motor and body weight increments. To my mind, not a big percentage weight difference between the two and actually pretty evenly distributed front and back. For reference an A8L and an A8 (short) are on the order of 300 lbs less for a given body length to either the W12 (in long) or the S8 (in short). I dredge all this up because the heavier the car, the more there is to control with a roll bar.
The baseline bar: The bar I pulled off (again, in a W12) was 4E0 511 407J. Its measured diameter was approximately 19.2mm, or only about 1 mm less than the S8 bar. Read on though, you will find it was already a "sport suspension" bar for D3's. Note just that 1 mm difference is a bit over a 10% increase in (solid) cross sectional area, so it is still likely meaningful in terms of stiffness. The part number as well as manufacture date was clearly visible in white printing along the bottom center area of the bar, basically in between the two sides of the exhaust. Makes it handy to check your installed part number. Unfortunately, the painted number on the new bar wasn't so clear, though it was well tagged to start.
The new and old bars, with the new bar label; note old bar part number and manufacture date is clearly visible:
<img src="http://pictureposter.audiworld.com/26081/img_3020.jpg">
Picture 1
More on stock bars: So mine was a 4E0 511 407J in a W12 as you can see in the picture just above. Turns out my parts listing says that is the "sport suspension" bar for any 4.2 A8/A8L. Clair also mentioned the Audi dealer parts system said it was the bar for cars with the BVJ motor, which is the FSI 4.2. Maybe they went to a stiffer bar automatically at that point. By the way in writing this up, I noticed the 2008 specs add 30 or 40 pounds to the curb weight of a 4.2 over prior years. Could be some of the new features and sound insulation, but I bet maybe they just caught the spec up in part for what I'm guessing may be a bit heavier 4.2 motor with FSI). Note there is no such thing in the US as a "sport suspension" W12 like there is for a 4.2. You might guess they would go for plush, though this bar use that I confirmed in the field contraindicates that. I am guessing when I pull the front bar off, it will also be equivalent to a sport suspension version on a 4.2. The air shocks are different in a sports suspension car too, but so far I haven't found that number on the car. Using the heavier bar does make some sense just given the extra car weight.
Also for reference, my A8 parts listing says the non-sport bar part number is 4E0 511 407D. I am hoping someone can climb under their non-sport 4.2 A8 or A8L at some point and confirm that, or do so if they replace their bar. I don't have a diameter measurement on that either if someone cares to contribute it. Remember, if you have a stock (non sport) bar, doing this with the S8 bar is taking you up "two notches." You could consider using just the sport bar instead. But my advice would be probably go all the way to the S8 bars if you want it stiffen it up in general. Stiffer bars do have some effect on the overall suspension and not just cornering, even if you leave the air shocks alone (which on an A8 with the cost and electronics, coupled with the MMI adjustability to start, is what I would do almost for sure).
How do I know which suspension I am supposed to have?: It's on the build sticker actually, which is copied in your service manual if it is all up to snuff, or if not on the sticker in the wheel well area in the trunk. It is the last code on the far right hand side of the second line of codes under "options." 1BK is a standard suspension (what mine says, but W12 style if you will), 2MA is a sport suspension, 2MB is an S8 suspension.
Getting ready for the install: Here I have to say Bentley was pretty worthless. It said I had to dismantle the whole rear exhaust, take off both wheels (not good for roll bars when trying to keep suspension loaded; more below) and also detach the rear air shocks from the suspension. Didn't matter for a W12 or any other D3--toward the rear what is under there is very similar, just somewhat bigger. No way was I headed this overblown direction (took Bentley only three lines to summarily say disassemble half the rear of the car!), just wasn't going to happen. From my C5 experience I knew you could typically snake them out with some levering and persuasion. But this bad boy was definitely meatier in the rear than a C5 and I could see those parking brake motors and lots of suspension bolt up points were looming.
Tools: as it rolled along, it was basically the normal metric sockets, various extensions, a torque wrench. A starred 12 point Allen type tool is needed to get the roll bar clamps off the body--mine is unmarked, but I think they would call it 10mm. You need to use a 3/8" drive or regular wrenches to get at the bar end bolt--it is close to the rear caliper parking brake motors. I usually used ½" drives otherwise. Also some Locktite to put on all the bolts, assuming you aren't going to bother replacing them. Definitely needed a drop light or something similar to see when doing some steps.
Manpower: it's a one person job straight up, unless you need help with the beer or a tool and parts jockey, and/or someone to talk to. Unlike the C5 where you have to wrestle the exhaust and one guy pulling and one guy working the bar in or out is best, with the approach I arrived at for the D3 it was just me all the way through without breaking a sweat.
A step-by-step breakdown of my technique. This is the home DIY version without mega pro tools. It differs radically from Bentley actually in the key approach--bar comes out sideways, not straight down and not at an odd angle by brute force like the C5--which is why I detail it here:
1. Drive rear wheels up on ramps (or do it on a four corner lift where the wheels still carry the weight). From experience with rollbars you typically want the suspension loaded up when you bolt the rollbar up. Helps avoid groaning noises too. Turned out I found out later this was very important for the trailing arm connection too. Put car in jack mode via MMI (more on why that later...).
Oh s%$#, Houston we have a problem...
<img src="http://pictureposter.audiworld.com/26081/img_3007.jpg">
Picture 2
2. Observe from underneath that the rear trailing suspension link on both sides is dead nuts in the way to possibly get the bar out. (The "oh s%$#" moment for me that caused me to pull out Bentley). The picture above is from directly below the driver's side rear trailing link. Up is toward the rear of the car. The roll bar is the black tubular part in the lower right middle that then heads behind the trailing link. Okay, so attack it. ABSOLUTELY mark the position of the mounting bolts for the inner trailing link bolt up point. Mark BOTH the front and rear with a Sharpie. Mark between the eccentric washer and the rear subframe it bolts to on both sides with at least two distinct perpendicular lines. This bolt controls rear toe, so if you fail to do this, you will be screwed and end up needing a rear alignment. Do it, or be sorry when you are forced to approximate! Once marking it, remove the bolt--18mm sockets on both sides. Without much force, you can pull the arm out of the subframe area and well out of the way. Do not remove the outer end--it would be a waste of time and no reason to at all.
Note in the next picture taken on the driver's side somewhat to the rear and below the suspension and again showing the obstruction caused by the trailing link, that I marked the washer and surrounding subframe. It is in the upper right. Nothing fancy. The antiroll bar is in the upper left part of the picture just at the shadow transition line.
<img src="http://pictureposter.audiworld.com/26081/img_3008_copy.jpg">
Picture 3
Now, with the link cleared away, notice below what a straight shot things are now to get at. The next picture was taken from directly below, also on the driver's side. You can see the bushing clamp bolt up point clearly at the aluminum subframe. Up is toward the back of the car (note part of muffler), down is to the front (note CV axle--curvature is close-in lens distortion not my car!):
<img src="http://pictureposter.audiworld.com/26081/img_3009.jpg">
Picture 4
3. Proceed to unbolt bar. Both the clamps that bolt to the rear subframe as well as at the ends where it bolts to the links. Here is where you need the 12 point allen head tool (apparently 10mm size; you can see the heads with the slight greenish tinge in the picture above), and clearance is tight on the sides for the end bolts because of the parking brake motor units on the back of the rear calipers. Still straight forward to do with a 3/8" socket drive (16mm). Doesn't seem to matter what order you do it in.
4. Pull the aluminum rubber bushing clamps off of the bushings; they interfere with trying to get the bar out otherwise. Notice in the picture above they actually extend through a punchout in part of the subframe that is sheet stock welded on.
5. Take one wheel off. Yup, here is where it goes totally off script and Bentley (and probably Audi for their tech training) completely missed the boat. There was no way I was going to drop the exhaust and all that stuff, especially in supersized W12 form. I tried snaking the bar out with it unbolted and the trailing links out of the way--the old C5 brute force idea--but there was no way it could have gone. I would have sawed it easily, but that doesn't help the install. But wait, I noticed it looked like a straight shot out the side if I took off a wheel. For anyone (probably not a regular D3 owner...) who ever took a steering rack out of, say a C3, it would be familiar. Seemed like removing either wheel would work. Based on how I had the car in my garage, I chose the rear right side one. I actually put the car in jack mode here, but I think you could do it back at step 1, unless it changes the suspension geometry a lot for the trailing link bolt removal at step 2. I doubt it does. Since I had it on ramps already, I used a floor jack (with a rubber pad) at the rear jack point and took the right rear of the car up another few inches (left side still on the ramp). I unbolted the wheel and put it well aside.
6. Insert jack stand. You need to get under the car later to get the new bar in. Safety first. The car was so high and a D3 underside is so smooth that it wasn't clear how to use a jack stand at first. Eventually I put my now freed up ramp base (mine are the metal two part type with a flat top) under the rear differential area and then jack standed from there to just under the differential case. It was well positioned and sturdy. Note if you use a drive-on four post type lift, it might get tricky here since you would now need to jack up one wheel and then get it off. Regardless, now remove the jacked up wheel.
7. With the wheel off, it was a cinch to pull the bar out. Much easier than threading it out on a C5 actually. Basically I simply rotated it by 180 degrees to the where the bent ends were now well clear of the bolt up points and rear rotor splash shield. Remember W12 brakes are bigger too, so if I could get it, any D3 would be as easy or easier. Pulled out sideways with a few twists and minor tugs. No major forcing or levering needed. A nice feeling, since now I knew the new one was definitely going in without a big hassle.
The money shot (with some near field blurring). The bar is rotated 180 degrees now. You can see the bolt hole at the near end toward the lower left. The bright somewhat fuzzy silver object with the half circle cutout is the right rear brake caliper with the wheel now off. Dropping straight down from what seems like the lower left of the brake caliper (actually maybe six inches behind it) is the near side trailing link which was unbolted and left out of the way. The reddish looking thing you see running vertically in the lower center is the same trailing link over on the far side (just distorted with the zoom effect and the lighting). In the upper middle and partially in the shadows you see the bar snaking back toward the far side. (The more pronounced bent pipe that seems to start behind the exhaust pipe in the center of the picture is actually part of the fuel vapor recovery system, not the roll bar.) That little white triangle in the upper middle is actually light all the way from the far side from gaps in the wheel spokes, thus showing how it is now a clear passage left to right to remove and reinsert the bar:
<img src="http://pictureposter.audiworld.com/26081/img_3018.jpg">
Picture 5
8. Start reassembly. Prepare new bar by removing the bolt up clamps that are likely on there from the dealer, plus all the paper label stuff. Clamps need to stay off until you bolt it up. They get in the way of threading it back in for starters. Remember visually which is the front and which is the rear of the clamp shell--the two shapes vary from front to back of the shell. Maybe mark an arrow with a Sharpie.
9. Thread bar back in like you pulled it out. Likely you will need to go under to get it unsnagged as you snake the "front" bent end of the bar past the exhaust pipes. But again, it's not a tough force fit. Here's where you better have that jack stand (or two) in place for sure, especially given the wheel is off completely.
9. Once the bar is in the general area it will end up, get underneath and get it closer to the final position.
10. At this point I started looking at the rear trailing links again. Good thing I did as it turned out. Basically with the car jacked up, and the rear suspension now unloaded this link will not bolt back in without at least undoing the other end, and probably then hammering on things. But wait, don't do that. The fix is easy.
11. Reinstall and torque wheel. Replace ramp (if you are using them). Remove jack stand. Lower car back down so rear suspension is fully weight bearing (but still up high on the ramps).
12. Swing the rear trailing links back into position, working the long rubber bushing through which the bolt will pass (visible in Picture 2 in the lower center) back up into the subframe area where it fits--it is now a straightforward fit that wasn't possible when the wheel was off and the suspension unloaded).
13. Now bolt back up the rear trailing links. Here is where you really need those alignment marks with the Sharpie from earlier. Note the bolts have slits perpendicular to the threads. Those need to face upward, as I found out after a quick false start. Start on either side. Put the bolt in from the front side and the eccentric washer on the rear side, Sharpie marks facing out (ask me how I learned that...). Apply a bit of Locktite. Then bolt it up to where it is just close to snug. Do ALL the tightening on the nut side only--that slit fits into the washer that has a tooth in the center hole to match and you don't want to force it. When you are close to snug, then turn the bolt on the head side (from the front of the car that is) just marginally WITHOUT holding the nut with any wrench. That causes the eccentric washer to move on the nut side because of the tooth in the washer that is in that bolt groove. Voila, you are now a rear alignment pro and setting the rear toe alignment back to where it started. Now line up your Sharpie marks on the rear eccentric washer exactly (or start over when you found the washer went in backwards and you don't see the marks...) by turning the bolt head from the front with the socket drive. Once you are there, snug up the nut a bit more so things won't move easily. Now, really nail the adjustment from the bolt head side too. If you look the Sharpie marks on that side won't quite be right. It is the minor play in the slot of the bolt transferring through to the back side washer. Simply turn the bolt head side back a bit the other way without touching the nut side. Now those marks should line up dead nuts too, and you should find the rear side unchanged. Assuming all is in order, now tighten the rear nut side down to torque (95nm).
14. Repeat #13 for other side trailing link.
15. Now proceed to get the bar bolted back up. Start by working those aluminum bushing shells onto the rubber. Note they bolt to the subframe only one way. Follow your marks from #8 (or if you laid them out as you removed them, how they were put down back in step 6). Or, if you just forgot or kicked them, just look for the outlines of the old ones on the rear subframe and match them up. Now work those bushing shells up toward their bolt up points. I stopped here without bolting them in to be sure all would work at the ends in the next step.
16. With the bushing clamps now on the (still loose) bar, work the ends of the bar into the ends of the suspension coupling links they bolt to--the dumbbell shaped things. The first side is easy. Just get a bolt (with a bit of Locktite) in there a few turns. For the other side, you need to force the bar back toward the side you first bolted loosely while also pushing the other coupling link dumbbell shaped thing outward to slide the bar end inside of it. It has a bit of a lip that holds it all together when lined up. Again, moderate force by hand was all it took. Just fit the bolt in a few turns.
17. Now with the ends loosely in place, bolt the bar up to the subframe. Those bushing clamp caps are a bit fussy getting into the punched out part of the subframe sheet plate aluminum, but again it should go by hand with no levering. Once generally in the area, apply Locktite to those 12 point bolts and work them all in loosely ( a few turns), doing both sides. I used the 12 point tool on a socket extension with no ratchet to turn them in, since the bolt heads are round, not six sided, and are hard to turn with just your fingers.
18. Now bolt the bar up tight. Doesn't seem to matter in terms of fit which part you do first. I did the ends first so the bushings would be bolted in most at their "rest" final position to minimize squeaking downstream. Torque the bar end bolts to 65nm. I did not have a 3/8" ratchet type torque wrench (there is no way to fit a ½" drive in there with the brake caliper in place, so I went with the feel o meter--decent pressure with a 3/8" drive. The swivel head type was best since the access to the bolt is a bit off angle and there isn't enough room to fit in a swiveling joint type socket extension. Then I bolted up the bushing clamp shells--gradually going back and forth among the bolts to ease everything in and then tight once I got to metal to metal contact of clamp shell to the subframe. Now torque these (25 nm). Low enough torque I had to use a 3/8" type torque wrench to set it low enough. Mine doesn't ratchet but that was fine here since you access them in a straight upward direction.
19. Okay if I remembered all the steps, it's about done. Of course if you have a W12, here is where you take a detour and unplug the solenoids on each side for those low speed exhaust valves that close off 2/3's of the flow at low speeds, but that's another posting...
20. Remove all tools. Get in car (in clean clothes...), take out of jack mode (it does it automatically if you forget), and drive it off the ramps carefully.
There you go, 20 logical steps later, all with pretty normal equipment and without first disassembling half your car too.
Front's are much easier from experience. Half a dozen no brainer type steps from the C5 experience and from what I have seen under the D3 too. That will be a future installment.
Total elapsed time, maybe 5 hours. But at least an hour and a half of that was checking out the exhaust and cleaning stuff up around the car. And I was doing lots of other household stuff off and on, and I explained to my teenage son how sway bars work. Now knowing Bentley is worthless and doing it this way, I would say about two hours + start to finish for the rear with the right tools nearby.
Road test results/comparison to follow.
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cqhall (04-26-2020)
02-23-2008, 10:18 PM
#2
AudiWorld Member
Umm, that was an amazing write up!!
I did this on an allroad in the past but assumed the D3 was going to be too daunting. You have demystified it for me and I may consider doing this sooner rather than later. Even though I have the sport suspension, some more roll control would be welcome.
thanks!!
thanks!!
02-24-2008, 02:17 AM
#5
AudiWorld Super User
Thread Starter
Now in my picture poster
<center><img src="http://pictureposter.audiworld.com/26081/audi_w12_stylized_silver_1280_size.jpg"></center><p>
It's a Photoshop artistic effect of some stock Audi A8 photography. I have it as my wallpaper on screen.
I will e mail you the bigger file.
It's a Photoshop artistic effect of some stock Audi A8 photography. I have it as my wallpaper on screen.
I will e mail you the bigger file.
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02-24-2008, 08:51 AM
#8
AudiWorld Super User
Thread Starter
Where it started.
<center><img src="http://pictureposter.audiworld.com/26081/audi_w12_silver_1280_size.jpg"></center><p>A nice picture to start.
02-24-2008, 09:26 AM
#9
AudiWorld Senior Member
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Patiently awaiting your impressions !
sadly I'm learning I'm not as good a wrench as I once thought I was... went to do the mirror swap ( A8 to S8 ) today and prompty shattered the passenger lense trying to remove it.... they seem to be pretty touchy.
so... think I'll let the shop swap those once I get the new Euro mirrors and maybe do the swaybars, pending your thoughts....
Time to complete ?
next mod ?
so... think I'll let the shop swap those once I get the new Euro mirrors and maybe do the swaybars, pending your thoughts....
Time to complete ?
next mod ?