944 automatic ATF leaks to diff

[Nicolas 2000]

Hi all!

Last year I bought a 944. Drove it for a while to check whether it was OK technically. It was, so we did a nice restauration. When finally finished, after 2 (!!) kilometers of enjoying my restored 944 and all that money spent, I noticed something had gone wrong in the transmission.

The complaints are:

-ATF level drops slowly, though I see no leak on the garage floor
-when first driving off, you have to warm up the car a bit and push the rev's before it shifts from 1 to 2. Once that is done, it works perfect for the rest of the trip.

I already changed the ATF + filter + pan rubber. Didn't help.

So now I *think* that I have the classic leak between tranny and differential (final drive). This causes ATF to leak into the diff, hence lower ATF level. And this causes the governor to get sticky, hence hard cold shift. Sounds logical? I haven't been able to check what's inside the diff yet, because I don't have the required hex tool nor a pump overhere.

In case of "yes, sounds logical", we (me and my car-handy father in law) would like to do the repair ourselves. In essence, the repair is:
-take governor out, clean, put back
-replace some seals
-refill diff and tranny

But this is where the problems start. Could you help me with the following 2 things:

-which seals, gaskets...(?) do I have to order? I have the PET catalog and mechanic's manual, but it is very unclear to me. On the www I see names such as "pinion seal", "governor drive seal", "final drive seal", but not how many of them I need, what else I might need and what their Porsche numbers are.
-any information about the procedure to follow? I know that I don't have to get the diff out to remove the governor, just loosen it and tilt it a bit. But what has to be done to replace the necessary seal(s)?

Thanks in advance! It would be lovely if we could do this ourselves at the cost of a few seals and fluids, because "right after total restoration" is not the moment where I want/can spend the 1000€+ for diff and/or tranny rebuild/replacement/significant mechanic job.

[Rod Schneider]

Sorry, I can't help with the part numbers, but in order to replace the shaft seals that keep the ATF from leaking into the final drive, you'll have to remove the transmission assembly and separate the final drive housing from the transmission housing. It's not difficult to do once the transmission is out, but you do have to be very careful to install the seals correctly and not damage them.

[Nicolas 2000]

Thanks for your reply! Any information is most welcome, as local forums gave zero replies due to lack of automatics in this part of the world.

Separating tranny from final drive is a matter of 4 bolts, so that should be OK.

Can I install these seals without taking the pinion shaft assembly out of the final drive? I hope I can keep the final drive in one piece and change the seals from outside. That would simplify things a lot.

Then I'd just have to find a healthy way of disconnecting the final drive from the transaxle. But for that, I think the workshop manual has a description.

[Nicolas 2000]

I've looked up more info. First conclusion: my digital workshop manual is missing the first page of the pinion seal replacement procedure. Sigh...

I'll add a range of drawings. Could you point out which things to replace?

As far as the procedure goes: I think the 2 seals that are most important are in that small round "box" (n°20 in drawing #2) bolted with 5 bolts onto the final drive cover (tranny side). And I *think* (read: hope) that I can remove that box without removing the pinion shaft. That would mean I wouldn't even have to disconnect the diff/final drive from the transaxle! So the diff could stay underneath the car. Unless I'm mistaken...

For the governor, the diff can also stay underneath the car, just loosen it a bit so it can be tilted (while attached to the transaxle).

As for seals, I was thinking about replacing:
-the two seals in the pinion "box"
-the large gasket between tranny and final drive (not in the PET catalog though...)
-the large and small ring seal between tranny and final drive
-the ring seal of the governor cover
-the governor shaft seal
-anything else? (apart from 80W90 oil and ATF if necessary, obviously )

Any comments Rod? With "the seals", did you mean the pair that's in this "5 bolt round box" at the pinnion shaft end?

[Rod Schneider]

Yes, the two seals are in the "five bolt box" (item 20). Once the tranny is separated from the final drive, you can remove the seal carrier (that #20) and replace the seals. The pinion shaft can stay in place. You should replace the other seals you mentioned as well. (Disclaimer: I've done this on an Audi 5000 transaxle, which is nearly identical in design. My 944's are both manuals........)

[Nicolas 2000]

Thank you so much! Audi 5000 is close enough for me to follow your lead. Sounds like a rather easy task then. The main challenge will be finding the right "shadetree tools" to get those 2 seals in without damaging them.

So, my shopping list is:

governor drive seal (087409133C) x1
governor sealing ring (011519345) x1
drive seals (087409529B) x2 (the ones in the seal carrier)
large ring seal between diff and tranny (010409549B) x1
small ring seal between diff and tranny (087409549) x1
small seal carrier sealing ring (089409637A) x1
"paper" gasket between diff and tranny x1 ??? (I don't think so; I think it is inside the tranny and not really between tranny and diff)

That seems to be the complete package.

I could also buy the kit 477 398 001 but that one is expensive (over 200) and overkill for my operation. One thing that makes it expensive is the tranny pan rubber (about €35 on its own) which I have already replaced one month ago. So I'll try to get a lower price for my wish list separately rather than the complete kit.

[Nicolas 2000]

The supplier can no longer deliver governor drive seal (087409133C).

Would this one be critical for the problem at hand? As it's the governor seal and I have a sticky governor (and the workshop manual mentions a damaged governor drive seal in this case), I'd like to have it replaced but it's getting hard to find this part...From what I have read, it apparently also is a hard one to replace (no stop, so you can easily push it into the diff, and a tight fit so easy to damage with shadetree tools)

Furthermore, I have more or less ignored the seals between torque converter and final drive. That's another place where ATF can enter the final drive. So I'll also order the 2 seals for that lid. That means the whole final drive has to come off the car, but so be it. Will make working on the governor easier. However, the metal torque converter seal (the one to be removed with a chisel) can't be ordered anymore. The 2 seals inside the lid however can. But I don't know if I can replace these without removing the metal torque converter seal? Or would said seal likely be reusable after having removed it with a chisel?

So that means that from the 3 possibilities (torque converter to final drive, governor shaft to final drive and transmission to final drive) of ATF to diff leaks, I'd only tackle the 2 between transmission/TC and final drive.

Now I've read that governor shaft is less likely to leak than the other two (even though the workshop manual only mentions the governor shaft ), but still...

Is it wise in your opinion to proceed with the gamble of the leak not being in the governor shaft seal?

On the bright side the supplier can deliver all the other seals required.

[Rod Schneider]

Well, it's kind of a judgement call, but most of the Audi problems were the 2 seals between the final drive and transmission. Since you're going to drop the whole thing anyway to do the torque convertor seals, you should be able to get a good look at the governor seal. It also might be worth considering taking the final drive portion to a transmission shop and let them do the seals.

[Nicolas 2000]

I have emailed 2 transmission shops with that exact same question. And I'm hunting for the governor seal and if possible the first TC seal as well.

If a transmission shop can do it for a reasonable price, they've got themselves a client. In that case, I would have to tell them 5 times that they don't need to do a mechanical overhaul though. There is some play in the diff, but nothing I (or the diff) can't live with so leave well enough alone. Ain't gonna get a super smooth ride out of this baby no matter how smooth the tranny would be.

Anyway, I hope I have a lead to the governor shaft seal tomorrow, or maybe to a good tranny shop.

The messages (not only from you) that the rear seal pair is a more likely cause than the governor shaft seal make me happy. Then again, there's Murphy.

I'll keep you informed! I hope this thread can help others in the future to get a full overview of anything related to these ATF leaks and eating diffs. Last time I drove my car, my diff still felt OK (also at 100MPH in second gear flooring the thing ) and I couldn't hear any clear whining from the back, so I have good hopes the thing still is in one piece mechanically. Obviously I'm not driving it anymore until this (probable) leak is fixed.

For completeness and future reference:

the pair of TC seals is 087409085B
the metal front TC seal is 010409568

[Nicolas 2000]

We've done the operation. We lost a lot of time because a supplier gave us simple type seals, which leaked like a seeve. They should keep 20 bars inside, and a simple oil can could be poured through them! So we went out to buy a good type of seal, redid the whole thing, and mounted everything back. The second time around, we could remove the entire gearbox and differential from underneath the car (on the driveway, without transmission jack!) in 50 minutes, which made me quite proud.

When we had the stuff apart, we saw evidence of mixed oils. The differential gear still was "like new" though! So I wasn't too late. The governor was sticky. I had to take the governor apart to the last bit to clean it. Only then did it move freely again.

For others: when your governor is really clean, the valve will shift simply due to gravity, by turning the governor 180° (holding it in your hand, not mounted in the car). If it is "sticky", this will not happen. Spraying WD40 in it without taking everything apart doesn't remove enough "dirt" to make it move that freely again.

The results so far:
-no more evidence of internal leaking (of course, I don't take it apart just to check but the levels seem stable)
-governor shifts also when cold

I'm happy!! Next time I'd do this job, I'd buy all seals myself instead of using a Porsche supplier, and I'd look for the top quality seal for each type. Once you're in there, there is no reason not to spend that extra 2€ per seal to get the bulletproof types. I'm quite confident now that the TC side will "never ever" leak again. The gearbox side has the prescribed type of seals, but these are quite good so should last years and years. I left the governor shaft seal alone, as advised by many. If my governor gets sticky again in a short time, then we'll go back in there and also replace that one. But let's not fear; the gearbox is shifting smoooooth and swift!