TSHong

It took 3.5 liters of Blue ATF to top of the trans. The transmission thumps going from 1st into 2nd gear. all the other gears shift perfectly with absolutely no slippage. Any ideas , TC or valve body?

mishar

Not sure what you are talking about. If you drop the pan it takes close to 6 liters to fill up. Without pan it would be about 5 liters. That's 4.2 engine. I believe W12 is close there. So, 3.5 liters doesn't fit. Unless you didn't pore out anything and you where that much short. If that is the case thump would be the least of a possible problems.

TSHong

The trans was that low on fluid. I did not drop the pan at all.

MP4.2+6.0

We need more info to try to help better.

For the O.P.:

I still l don't understand how you were 3.5L down. That's a symptom of something significant, not the problem. 3.5L of fluid doesn't just disappear. Likely you have a serious leak. Otherwise, someone serviced it incompetently. So,
Can you describe the thump more? Have you driven other Audi's with a similar problem as points of comparison? Also, realize when you really floor a W12, the shifting is pretty abrupt from 1-2; 450HP and about 400 ft. lbs will do that! Also owning a C5 (A6 4.2) with the prior five speed, the W12 is very smooth at easy and mid throttle, but also much crisper and faster than the older 4.2 was. Is yours smooth otherwise, like at part throttle?

And earlier, I think you mentioned a bad front torque support (which is a serious fix effort, not just a few hours on a W12). Presumably you will get some engine/drivetrain shifting from that. Could that be it? Have you looked at the other two primary motor mounts? When I posted about my failed torque support (fixed near end of CPO), one response w/ apparent experience was to look at other mounts too and they may be bad or on their way out. Net, look at all your mounts.

TSHong

I should have explained on this thread that the trans pan was leaking. there was a pan bolt that was not even finger tight. I re-torqued all the bolts and cleaned the pan are so I will check again to see if it's leaking or not.

I did not think about motor mounts or the torque struts. when Audi did a PPI, they said the right torque strut was leaking, not blown out so I did not really think about that but worth looking into.

I'm coming from a D2 4.2 so yes the 6.0 has so much more power. It is a good thump when the trans shifts from 1st to second or smaller when 2nd to first only. All other gears are perfect.

MP4.2+6.0

1. so, since I have the C5 4.2 w/ the same 5HP24 that your D2 has, the 1-2 full throttle shift in the W12 is much faster and pronounced than the 5HP24. Owned that one since new including a ZF rebuild, so know its feel when operating well. More of the fluid shift feel under hard load than the W12. I really haven't punched mine a lot recently, but the acceleration is so pronounced and so fast it can feel almost violent from 1 to 2.

2. Do check the torque mount as a suspect, plus the main motor mounts As the name implies, it is meant to offset that rocking; 1-2 is presumably where you would feel it most, and most quickly. Mine had cracked and the fluid visibly run out. Prior to that repair I think I recall the 1-2 full power shifts feeling somewhat more abrupt than now.

3. I don't recall other posts over the years about any systemic trouble on 1-2, particularly W12. Makes me wonder then more about areas like #2, though its possible you have some internal tranny issue.

4. The loose pan still seems odd. Not characteristic for OE Audi or ZF. Do you have any service history on the tranny specifically? Dealers don't usually touch the trannies except for gasket leaks and for reluctant forklift replaces for any perceived internal issues (excepting the "hoot" issue on the 4.2's leading to the fluid change plus reflash). And, is it possible it did not get the Blue fluid in it if someone else topped it up previously too--perhaps w/ the gold or even something even more off spec. for the W12? Where this leads is to consider giving it a full drain and filter replace if it continues to feel rough, you don't have a comprehensive view of the car's service history, and you have eliminated things like #2 as issues. Will cost some money for the fluid, filter and gasket. But, since the average drain probably gets close to 2/3 of the fluid out and you have already supplemented about 1/3 w new Blue for starters, I think the math is you will then have about 7/9's of it now changed to fresh and known correct fluid.

TSHong

I did not have time to look at my mounts today but I found that if you accelerate harder, the thump is less pronounced. This seems like it would rule out the mounts but since the motor mounts have electronics, I don't know. Since I was shaking out my hand controls and the thump, I was really babying the trans but I notice in tip mode and Smode , it was less pronounces. Seems like the quicker the shift needs to be, it's less noticeable. Any thoughts?

JohnnyJ A6Q

Thomas, give me a call, running out the door now but call my cell.
you got 5 mins to call LOL

Bangerla

In some ways it seems too aggressive at trying to upshift in D mode, since you will be in 4th gear by the time you cross and intersection when starting from a standstill. Downshifts in the 3-1 range can occasionally be abrupt as well. I have just become accustomed to it as being the nature of the beast. When I first bought the car, I too thought something was wrong, since it seemed to shudder at low speeds when taking off. Then noticed this was from it shifting every 7-8 mph.

MP4.2+6.0

1. Per my prior post, again if you don't have service history comfort and tranny was leaking and down on fluid, I would drain and refill it. My sense is it is fairly likely it was tampered with by someone not knowing really what they were doing--at least its a worry. Cost will be in the $4-500 range realistically w/ blue, vs. perhaps 15-20x that if tranny blows.

2. Per our message exchange, yes maybe try adaptation--both TCU AND throttle.

3. The motor mounts are electronic, but I think the torque one may not be. Would have to look again. Mine is smoother (really smooth as a 12...) since the replace, though its at or just off idle where the change seems more obvious (more like a 4.2 or other V8 before, now running almost unnoticable). But, per my prior posts, a difficult replace per Bentley, even including essentially machining a part in place by drilling a hole to allow removal of a key bolt Audi pretty obviously overlooked in the design.