Easy Final Drive Differential Fluid Change

audi_marv · 12-19-2011, 02:32 PM

Hey Everyone,
As a courtesy, and for therapy

, I thought it a good idea to pass this procedure on so others can try this without running into the same painful issues that I did.

Apparently, Audi Mfg. considered the Diff Fluid "Lifetime Fluid", but dedicated Audi owners know better. To be safe, and possibly spare you a ton of $$$, The Diff Fluid should be checked or changed at least once a year. This method should work on 5000's and 200's, but not sure on 100's or the V8's

To change the Diff Fluid, you will need :

- Multi-Purpose Siphon Pump (bought a Penzoil one from Meijer's for 8 bucks). Funnell, with fairly long neck.

- Magnetic 10mm socket is desired (I used a 2" long tubular magnet which fit inside a deep well socket).

- 1-2 ft. wratchet wrench extension (or multiple shorter extensions).

- Strips of duct tape.

- 1 Ltr./quart Gear Oil. 75-90w reg ($5.00), or synthetic.

- Based on outside temp, you may want to drive car around the block to warm up gear oil for easy siphoning.

Start by locating the Speedometer Gear Connector. Located on the Trans housing, just below the steering rack.
I tied away heater hoses and wires, and removed dist. cap, for better access.

1. Disconnect press-on Speedo Gear connector.

2. Thru trans. housing, locate Speedo Gear lockplate, and 10mm bolt. Use extensions and magnetic 10mm socket to remove bolt. DO NOT let bolt fall into tranny housing (speaking from experience). If you don't have a magnetic socket/telescoping magnet, then loosen bolt, apply strip of duct tape to bolt head and washer, and remove.

3. Place magnet, or duct tape strips, on Speedo Gear lockplate, and rotate gear out of housing, not allowing lockplate to
fall into housing....(yes, i did this too during re-install

4. Once gear is removed, you can see 2" round opening to place siphon hose into. Suction gear oil out.....s/b about 1L./quart.

5. Using funnel, replace gear oil.

6. Replace gear, lockplate, and bolt, leaving on duct tape or magnets....and "Viola"...you're done !!!

--- a magnet on a long wire is great for fishing out the bolt or lockplate from the tranny housing. 10mm bolt is also under a lot of stress due to speedo gear, so I replaced with a new one ---

I was shocked to see I had suctioned out about 2 quarts of oil. Thought at first I was mistakenly sucking out tranny fluid, but then realized the seal between tranny and gear fluid was bad, and that tranny fluid had seeped into the final drive area.
FRAK !!!

Guess this explains the oil residue on top of the trans housing, which a mechanic told me was coming from my Steering Rack !! There are two small plastic, bobble-head type, vent openings on top of the trans housing. One for trans fluid overflow, and the other for diff. fluid overflow.

So now I get to deal with the fluid swaps. I'm going to do this again in 2-3 months to see how much has transferred over. Easy, since now I can do this in 1/2 hour, have the siphon pump, and the gear oil is cheap.

I thought if there's a lot of transfer, to try 85-140w gear oil to slow down the thinning out process. Any comments on this ???? (yes, due to the 85w thickness, I'll switch oils after winter). Another option is to try a Bar's Leak Seal Softening additive to slow down the transfer.

I read a post here from 2000 that urged me to try this. Just didn't have the desire to do it the Bentley way, nor had a 17mm allen wrench on hand. Thanks to Tom Serrago for the 2000 post......if you're still out there.

So now you guys know what I know. Happy Motoring !!!!
Marv

one5k · 12-19-2011, 03:30 PM

i changed my seals between the trans and diff less than 20k miles ago. already fluid has mixed. i think it's just going to continue to happen. i'll just continue to top off the diff and drain and fill the tranny as often as i feel like it.

audi_marv · 12-23-2011, 10:37 AM

20k sounds about the time mine started leaking too. Not sure why diff. seal technology hasn't gotten any better in the past 20+ years.

I plan on focusing on draining and filling the diff fluid more than the tranny fluid. The diff fluid mixing with the tranny fluid won't hurt. Its the tranny fluid in the diff chamber that causes the damage.

I cleaned off the top of the trans housing where the vent caps are, and the moment i see any fluid there, then i'll change out the diff fluid.

Looking into using Amsoil the next time around. They say it contains seal softeners that will swell and stop a seal leak without eventually harming the seal itself.

one5k · 12-23-2011, 02:45 PM

yeah. but i pulled down the trans pan and couldn't believe the amount of sludge in there already from the gear oil. i had it spotless when i changed the seals..

audi_marv · 04-29-2012, 03:58 PM

Update: Suctioned out the tranny fluid and dropped the trans pan yesterday, and there was just a little black sludge at the bottom of the pan, probably from the diff fluid mixing in. I was surprised that there were hardly no metal shavings at the pan magnet, or in the screen filter.

Only suctioned out about 2.2 qts of tranny fluid, where the Bentley says you should get 3.2. Suctioned out the gear oil, and got 2 qts., when I should have only gotten one. Fluid had not started coming out of the vent caps yet.

So after roughly 4 months/4k miles, one quart of tranny fluid had leaked over to the diff fluid. Filled tranny this time with Maxlife ATF, to see if this may slow fluid transfer. Used Valvoline 85w145 diff fluid, which the tranny fluid should thin down over time. The temp will hit 80 this week, so not too concerned about the diff fluid being too thick at start up.

Guess I'll check this again in Aug/Sept. Will probably only replace the diff fluid, and top up the tranny fluid, if the Maxlife does'nt work. Got the process down to 1/2 hour, so doing this every 4-5 months won't be a big deal.

audi_marv · 10-29-2012, 09:12 AM

Next Update: Good info for new owners.....

Saw a few drips in the garage, so figured it was time to check the diff fluid. Actually, the check was a bit overdue.

Suctioned out about 2.3 quarts of diff fluid this time. I was hoping the Maxlife trans fluid might slow down the transfer rate, but no go. The 85-140w fluid was no problem during the summer, and changed to 80-90w for the winter. I'll give it another 4-5 months and revisit this again. Hopefully, i'm saving my tranny from a big buck overhaul by doing this.

I'm thinking its the seal between the torque converter and the final drive thats leaking. Unknown if this seal was changed during the last rebuild.

When i previously dropped the gear lockplate into the tranny housing, there was fluid in there. Guess I can suction this fluid out, along with the trans fluid thru the dipstick, to get the all of the tranny fluid out ?

Any thoughts on this....

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Welcome to AudiWorld!
		Welcome to AudiWorld.com. You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join AudiWorld.com today!

12-19-2011, 03:30 PM	#2
one5k Audiworld Junior Member Garage is empty, add now Join Date: Mar 2008 Posts: 78	i changed my seals between the trans and diff less than 20k miles ago. already fluid has mixed. i think it's just going to continue to happen. i'll just continue to top off the diff and drain and fill the tranny as often as i feel like it.

12-23-2011, 10:37 AM	#3
audi_marv AudiWorld Member Garage is empty, add now Join Date: May 2008 Location: Zinzinnati, Ohio Posts: 280	20k sounds about the time mine started leaking too. Not sure why diff. seal technology hasn't gotten any better in the past 20+ years. I plan on focusing on draining and filling the diff fluid more than the tranny fluid. The diff fluid mixing with the tranny fluid won't hurt. Its the tranny fluid in the diff chamber that causes the damage. I cleaned off the top of the trans housing where the vent caps are, and the moment i see any fluid there, then i'll change out the diff fluid. Looking into using Amsoil the next time around. They say it contains seal softeners that will swell and stop a seal leak without eventually harming the seal itself.

12-23-2011, 02:45 PM	#4
one5k Audiworld Junior Member Garage is empty, add now Join Date: Mar 2008 Posts: 78	yeah. but i pulled down the trans pan and couldn't believe the amount of sludge in there already from the gear oil. i had it spotless when i changed the seals..

04-29-2012, 03:58 PM	#5
audi_marv AudiWorld Member Garage is empty, add now Join Date: May 2008 Location: Zinzinnati, Ohio Posts: 280	Update: Suctioned out the tranny fluid and dropped the trans pan yesterday, and there was just a little black sludge at the bottom of the pan, probably from the diff fluid mixing in. I was surprised that there were hardly no metal shavings at the pan magnet, or in the screen filter. Only suctioned out about 2.2 qts of tranny fluid, where the Bentley says you should get 3.2. Suctioned out the gear oil, and got 2 qts., when I should have only gotten one. Fluid had not started coming out of the vent caps yet. So after roughly 4 months/4k miles, one quart of tranny fluid had leaked over to the diff fluid. Filled tranny this time with Maxlife ATF, to see if this may slow fluid transfer. Used Valvoline 85w145 diff fluid, which the tranny fluid should thin down over time. The temp will hit 80 this week, so not too concerned about the diff fluid being too thick at start up. Guess I'll check this again in Aug/Sept. Will probably only replace the diff fluid, and top up the tranny fluid, if the Maxlife does'nt work. Got the process down to 1/2 hour, so doing this every 4-5 months won't be a big deal.

10-29-2012, 09:12 AM	#6
audi_marv AudiWorld Member Garage is empty, add now Join Date: May 2008 Location: Zinzinnati, Ohio Posts: 280	Next Update: Good info for new owners..... Saw a few drips in the garage, so figured it was time to check the diff fluid. Actually, the check was a bit overdue. Suctioned out about 2.3 quarts of diff fluid this time. I was hoping the Maxlife trans fluid might slow down the transfer rate, but no go. The 85-140w fluid was no problem during the summer, and changed to 80-90w for the winter. I'll give it another 4-5 months and revisit this again. Hopefully, i'm saving my tranny from a big buck overhaul by doing this. I'm thinking its the seal between the torque converter and the final drive thats leaking. Unknown if this seal was changed during the last rebuild. When i previously dropped the gear lockplate into the tranny housing, there was fluid in there. Guess I can suction this fluid out, along with the trans fluid thru the dipstick, to get the all of the tranny fluid out ? Any thoughts on this....