View Full Version : Quattro system not working. 1999.5 A4 1.8T

10-16-2018, 02:51 PM
So when I bought the car, the driveshaft was disconnected because the car had bigger tires in the back compared to the front. I got a new set of winter wheels with all the same tires with the same wear. I went to go put the driveshaft in and the output mount for the driveshaft coming from the transmission just spun with no force behind it. I still went and put the driveshaft to see what would happen.

I drove it out of the garage and went to a gravel parking lot and it still will just oversteer while trying to do a small drift. No power is getting to the rear wheels. A quick drop of the clutch proved my point when just the front wheels lost traction. The rear diff and axles are all there and work fine because I had to hold the wheels while a friend tightened the bolts on the driveshaft. But the fact that the front output from the trans just spun makes me believe the center diff is broken?

There are no grinding noises coming from anywhere. Drives, shifts, and accelerates just fine. Is the center diff in with the trans or is it a separate piece? From pictures it looks like it can be removed from the trans without removing the whole transmission. Any help would be great! I didnít buy another A4 for the AWD system to be a bust just in time for winter haha.

10-16-2018, 05:18 PM
If the car moved, everything is fine. If anything in the drivetrain is broken, it won't move. The car is biased to the front wheels

10-16-2018, 05:42 PM
I just donít understand because my old 99 A4 would kick out in gravel and as hard as I tried this one did not. Iím convinced that something is broken. And it shouldnít do a standing burnout in first after letting the clutch down. It acts nothing like my last A4 that was identical. If the car can still work missing a driveshaft I feel like a broken component sending power to the rear can be broken and still have it work.

10-17-2018, 02:32 AM
If the car was running with the driveshaft disconnected to the rear then the center differential has probably been welded up or something like that.

10-17-2018, 06:05 AM
^This. An A4 quattro will not move an inch under its own power with the driveshaft removed. If yours did, it's been modified.

You can pull the tail section off and inspect what's been done. It will probably require a donor torsen center differential to return the quattro feature to working order. Also, please provide photos of whatever modifications you find. This is interesting.

10-17-2018, 11:39 AM
^I will have too look into that. Iím still kinda fresh to Audi. But yeah the car as it sits drives fine and it was driving fine with no driveshaft. Was sitting in the trunk since I bought the car. And I can take that center diff off while the trans is on the car.

10-17-2018, 01:52 PM
If that is a question: yes, you are able to remove the tailshaft housing and the center Torsen T1 differential unit while the transmission is mounted in the car. Just need the driveshaft removed first. Here's a little guide:


10-18-2018, 02:58 PM
So I jacked up the rear of the car and the driveshaft spun the rear wheels. But the front wheels were on the ground and the car was in gear. Donít think theyíre supposed to move? Investigation continues...

10-20-2018, 02:51 PM
So I finally had some time to pull the center diff off and you guys were correct. It has been welded. Anybody have any idea where to get a new one? Iíll post pics when I get home to my laptop since itís hard to do it on mobile. Tried looking one up online but it just shows rear diffs.

10-20-2018, 03:59 PM
Find someone that wants to go RWD and just swap them diffs. Or go RWD yourself 😃. That would be easiest. Next would be pull one at the yard or find someone selling one.

10-25-2018, 08:58 PM
So here are the pictures of the diff. You can see the welds on it. So here is my theory. The guy had two different tires front and rear. Like completely different tires. So I feel he ran those tires and over time the center diff just started to eat itself. These center differentials are hard to find on their own so the owners dad I believe just removed the driveshaft. Then found out that it wouldn't be that easy so then he welded the diff to make it all work for cheap. The diff that was in the car makes a lot of noise even with being welded and there was a LOT of metal shavings on the magnet. The new one is out of basically a clone of my car. Same year, engine, trans, paint, interior, options and everything. Its got 80k more miles that my car but it seems to be all good. For $50 it was a steal. Tomorrow I'm going to put the new one in, throw in some gear oil, and give it a drive. I am praying to god that nothing is wrong with the rear diff.


10-26-2018, 06:18 PM
Thanks for posting the picture. I'd probably agree with your timeline of the failure event. That's an interesting way for the guy to "fix" it.

Glad you found a torsen so cheap. Rear diffs are mega cheap, too. So no worries there.

10-26-2018, 08:26 PM
Now take said welded diff and sell for $50.

10-29-2018, 09:03 AM
Now take said welded diff and sell for $50.

I think this one is done for in many ways. It makes a lot of noise when turning the shaft and it doesnít turn the back side at all. Iíll keep it around in case something were to happen.

10-29-2018, 09:05 AM
Also, the car works! Went to the gravel pit and the car got sideways no problem! Been driving it for over 3 days and I have had no issues, noises, or leaks!

10-29-2018, 11:01 AM
You have saved a quattro. Good on you, sir. [az]