Newly Rebuilt 915 Tranny - Major Fluid Leak

goldgunner · 10-15-2006, 10:42 AM

Background:
Around a year ago I had my 915 tranny rebuild by a local Porsche - Audi shop that are locally recognized as capable - but to my knowledge not in the same category as Mayo and Zim's. But, according to them they've re-built hundreds of 915's as well as countless engines.

I had some earlier concerns that I posted on this thread:
Transmission Bracket - For Clutch Cable?

Now here it is a year later and I’m coming close to completing the rebuild – finally getting the car on the road for short runs to tune my EFI settings.
In the middle of the tuning process I had to re-drop the engine and replace the main flywheel crankshaft seal because of a more than acceptable oil leak.
With probably around a total 1 hour road time I’ve no more engine oil leaks – what so ever.

But, I did start to notice some bluish transmission drops slowly accumulating at the bottom and bottom front of the transmission housing.
Not too bad and not bad enough to drop the engine and transmission to get to the nuts to re-tighten what I assumed were somewhat loose flange gaskets.

Now, today, as I do some more tuning I happen to look into the shifter coupling that I’ve left open to yet perform some fine adjustments and what I see is a Pool of Blue Transmission Fluid almost over the lowest recesses of that area. So while I’m soaking this up and trying to calm down, I’m writing this to get a reality check:

This transmission fluid is most likely from the seal at the transmission 'nose' shift bar end? What is the correct name for this seal?

Is there any excuse or reason why this seal should so apparently completely fail after little more than 1 hour post rebuild road time?

After dropping the freaking engine and transmission again (so freaking close to completing this project and getting on the freaking road), take the transmission back to the same shop for their ‘warranty’ repair? Or give up on them and go elsewhere – like Mayo?

Or is this a seal that I should replace myself? Can this be done without disassembly of the tranny case?

Thoughts?

Thanks in advance,
Jim

78-911SC · 10-15-2006, 12:41 PM

Jim I had the same thing happen and I found out I had put a little to much fluid in and it was coming out the air vent on the top of the tranny. Let some out, cleaned the tranny as best I could and it cleared the problem up. Hope it's something simple.

Jim Sims · 10-15-2006, 12:47 PM

Make sure the hole in the vent is facing forward. Installed properly the shift rod seal should last more than an hour, provided the shift rod isn't bent or scored in the area that runs on the seal. The seal can be replaced in the car but it's "a lot easier" to do with the transmission out and by taking the front cover off at the cost of a new $1.00 paper gasket and of course a new shift seal. Check the vent orientation first though.

goldgunner · 01:25 PM

Thanks Fellows: Earlier in the process I had discovered that the tranny vent was incorrectly facing towards the rear of the car - with the typical result that tranmission fluid was 'blowing' out of that vent. I turned the vent to face towards the front of the car and that solved that problem.

I've inspected the tranny top, bottom and sides and no evidence of significant leaks. Hence my interpretation that it must be the 'nose' seal around the shift rod. I don't see how any other leak could end up coming out in the tunnel at the shift coupling...

Does my description make sense?

Is it possible that an overfill condition would cause this out the shift rod seal? Is there meaningful pressure behind that seal?

goldgunner · 10-15-2006, 01:56 PM

Follow on:
Jacked it up, got underneath and slid the rubber boot off the nose of the transmission from around the shift rod and - yup - the boot was full of transmission fluid, the shift rod seal is wet and that's what's leaking.

I suppose with some careful picking I could get the old seal off in-situ...
however it looks like pressing a new seal in would be dicey to ensure squareness, but possible.

Any thoughts, please?

thanks,
jim

Jim Sims · 10-15-2006, 02:37 PM

"I suppose with some careful picking I could get the old seal off in-situ...
however it looks like pressing a new seal in would be dicey to ensure squareness, but possible."

This job has been done in place, but it's a "pain." I think it's in 101 projects?

goldgunner · 02:46 PM

Another follow on:

Jacked up the car to level and removed the transmission fill plug.

Surprise~! A LOT of fluid came out... And a lot came out after I repluged it and got a large rag to catch it in. This on top of the Large amount of fluid that had come thru the front seal into the tunnel at the shift coupling.

Only thing I can figure is that my professional rebuilders had my 915 on its side to put that much fluid in...maybe they assigned it to their 'shop turd' to do - without instructions. Maybe...whatever...should never have had that much fluid in it.

Guess I'll continue on 'as is' and see if: A. Reducing the fluid volume solves the fluid leak thru the seal, and B. Whether any change in transmission function occurs.

(I'll buy and bring in a new seal - just in case)

Jim Sims · 10-15-2006, 02:50 PM

I guess they wanted to make sure you got your money's worth - wasn't this the $1900 rebuild job? That was reasonable price for a nominal rebuild but they could have least put the right amount of oil in. If the transmission was run with that much oil perhaps it could have blown the front shift rod seal although I'm surprised the pressure didn't get relieved out the vent. Is the vent fully clear? Reminds me of a friends saying: "I can make mistakes myself cheaper than I can pay a professional to make mistakes."

goldgunner · 10-15-2006, 02:57 PM

Jim - I wondered about the vent: seems if there was enough excess pressure to blow thru the front shift rod seal, there would have been fluid coming out of the vent - there was none.

While I have it jacked up, I'll figure out a way to probe the vent opening and ensure that there is a clear passage into the case: should be...

Yes - this was the $ 1900 rebuild that I wasn't thrilled about - from what I could see on the outside. Guess I should have been happy with the outside and more concerned about the inside. My tuning runs have been fairly aggressive and no transmission issues (yet) so it's doubtful there's a hunk of gears or something at the bottom of the case taking up space and pushing the fluid high out the fill hole.