thrash

if so, can you do a seal-replacement as a preventative measure?

i know very little about auto trannies. is the seal replacement more or less involved than doing something like a front or rear main seal replacement on an engine? will the fluid-"logic" board in the transmission need to come apart?

is a seal replacement on this gearbox within the scope of a normal automatic transmission service center?

BforestS8

once a D2 has 100k they get hungry for $$$ and repair

jazbo123

My 98 has 160k. Other than needing a "Tozo job" it's been great.

TwoTonic

The Audi/ZF failures, at least in the early D2s, seem like a class problem. Few transmissions seem to have failed in warranty, but over 100K they tend to be a commonly failing item.

The GM products run the gamut. We actually have 4 late-model Suburbans in the current fleet and tow heavily with two of them. Both have the more recent 4L80E/4L85E series and those seem to be bullet-proof. We regularly tow with GVW > 10,000# in the mountains and approach 200,000 miles without problems.
The early series 4L60E transmission, when used in the Suburbans for towing, were very problematic. Lots of them would grenade at 70-80K. Those were mostly in the 1/2 T series, however. If you ever see a 1/2T Suburban/Yukon that was used for towing-- run the other way.

On the other hand, I also have a B-Body Impala with an LT-4 396 stroker and the stock 4L60E in it. This is a 450 RWHP car and the only work on the 4L60E has been a TransGo kit to beef up the valving-- it shifts WAY firmer than any of the three D2s I have. All three Audis vary from 'sloppy' shifts to 'will not go into reverse at all', so I'm not terribly happy with any of the ZFs I own in the A8s, even though I love the Audis.

The Impala seems like a reasonable proxy for the Audi A8. Both are 4000# sedans with 300HP. There are guys over on the Impala forums running 500 HP turbo set-ups through pretty stock 4L60s without a lot of problems. (Of course, with them all that wheelspin probably mitigates the extreme torque stressed being transmitted via the driveline. )

I don't doubt that a 'built' ZF box would run longer and more reliably, but it doesn't seem reasonable to have to do preventive maintenance every 60-80,000 miles-- especially given the cost to pull and repair. Whether it's a 50 cent seal or a $500 planetary that fails, it still ends up being a weak point in what is otherwise a stellar car.

Your experience with the ZFs is formidable... I'd be certain that an upgrade for the stock D2 ZFs would be extremely well-received. I'd love to upgrade two of my three A8s (the third one is definitely getting an S4 6MT like yours-- it's waiting in the shop to be installed) if it were possible to do so.

CalG

Without real data, our conclusions about 5HP24a transmission failures is only so much sentiment and emotion. Most all makers have transmission difficulties. Pheonix et al. are not in business just for Audi! ;-) Our list membership might be over represented by those who HAVE troubles. Why else would one "look for assistance"?

At any rate, transmissions are complicated. Small parts that fail make big trouble. Most failures have nothing to do with design or loading. $5 Rubber parts.... likely not even produced by ZF, and certainly not by Audi.

Certainly it does not pay to "Service" a transmission by performing a complete overhaul as "preventive". But regular fluid and filter changes are just good practice.

Someday statistics may be presented and we can all rest our minds on the issues of unreasonable unreliability. Yes or no I'll accept either proof. Until then, with 130K miles and still driving fine, I'm happy with the D2 as an overall package.

CalG