Silver90Quattro

Has anyone ever experience or heard of the rear diff failing? As in: LOUD humming/groaning at virtually all speeds, but loudest at 35mph and 50ish? I replaced the left rear wheel bearing thinking it was that (only 50k miles on bearing since first replacement), but noise is still there and getting worse. About to replace right rear wheel bearing (only 50k miles on that bearing), but I dont want to do that and have it be the diff all along... I have never run it dry (seals leak, common problem) and have always used Synthetic since 163,200... Car has 227,600 on it now.
Thanks very much for your time!

Brian
'88 90quattro

MikTip

Not uncommon..........especially with 227,600 miles! ;O)

RS4000

i replaced the driveshaft bearing.
although, you can get new diffs from force5 for $50 each.

Silver90Quattro

Thanks for the reply... yes I have already replaced my Ctr. DS Bearing, is this what you are refering to, or you mean a bearing within the diff?

Silver90Quattro

Thank you very much for the reply, you guys are so great!
What fails within the diff that might cause the noise I am describing?
Are replacement parts avaiable?
What other diffs might fit, with a taller ratio than the stock 90q? I am sick of turning like 3600rpm at 80mph on expressways... seems hard on engine and LOUD at that speed!
The car is not fast anyway, so it does not really bother me if acceration suffers slightly. My mother has a '93 100csq with the 5spd. Nice smoooth quiet car! Any chance that diff or a later model 90 series diff would fit?
Any ideas?
Thanks a bunch!

MikTip

Replacement gears are very rare & expensive. Plus require special tools to install & setup.

Basically you can get rear diffs from 1988-1992 Audi's

Maybe some here-<ul><li><a href="http://www.car-parts.com">http://www.car-parts.com</a</li></ul>

RS4000

there's a bearing where the DS meets the diff, that's what makes noise

Silver90Quattro

"Basically you can get rear diffs from 1988-1992 Audi's"

So I can use any rear diff from 88-92 Audis?
Is this what you mean?
Again, I would like to try something a little taller.

Thanks so much, that parts site is GREAT!

repeater

There really isn't anything other than 4.11.

cuatrokoop

or change the final drive on both the trans. and rear diff.

Doing the ring and pinion (or crown and pinion) is time consuming and requires a great deal of setup due to the number of shims required to maintain the tolerances and get a proper tooth/tooth interface between the gears. Best left up to a professional.

A transmission swap with one that has the same final drive ratio but different gear ratios is something you could do if you have the tools, time, and knowledge/manuals.