Diff Oil Leak
 

On my 99' 2.5 Tiptronic I have a oil leak from the diff. It seems to be coming from behind the driveshaft, between the diff and the CV joint.

Any pointers?

I have a 2001 boxster S, and I just fixed a similar leak. Symptom was a very slow drip from the passenger side of the differential, most visible on the output shaft that the rear passenger side axle bolts into, and behind the CV joint. The top of the aluminum transmission protector just below the axle was slightly wet as well. In my case the problem was the differential output shaft seal. Seems to be a common problem. Relatively easy fix, $25 part - I have the 5 speed ZF transmission; a ZF seal is easy to find as many cars use this transmission. You should also drain and refill your differential oil when doing this procedure.



The procedure from my memory:



Raise the boxster

Remove the aluminum transmission protection plate

Detach the rear sway bar from the mounts behind the transmission

Remove the passenger side rear wheel
Unbolt the passenger side rear axle from the transmission (5 or 6 fairly large allen bolts) and drop it out of the way

Remove the transmission output shaft (as I recall it's held in by a central torx bolt, once this is removed it slides out easily)
Remove the differential filler plug and suck all of the old differential gear oil out with your mity vac. Mine was gross.

Clean the newly exposed area behind the output shaft thoroughly with brake cleaner

Clean the output shaft itself thoroughly

Remove the damaged seal. Be very careful to keep the area clean and to not scratch the housing where it fits into. There is a fancy ZF / Porsche special tool for this, but I used a needle nosed pliers and a vinyl coated bar to get the old seal out and it wasn't too bad.

Clean again thoroughly
Rub some fresh differential oil on the inner and outer edges of the new seal.

Tap in the new differential output shaft seal. You need something round and hard just barely smaller in diameter than the new seal to push it in. Make sure you get it in flat and even. It taps in pretty easily.

Reinstall the output shaft, reinstall the keeper bolt.

Refill the differential with fresh gear oil until it overflows the filler hole. I filled, turned both wheels by hand a bunch of times, sucked out the new dirty / clean mix, and refilled again with fresh fluid to get as much of the old gunk out as I could.

Reattach everything you removed in the opposite order.



Pictures and instructions for much of this are in the 100 porsche projects section on Pelican and in the 100 projects book - look for the procedures to replace the shocks (that talks about how to remove and reinstall the rear drive axles) and also look for the section on how to change the differential gear oil.


As I recall it's also possible for a leak in this area to be coming from an o-ring inside the differential, but the differential output shaft seal seems to be the most common place for a slow leak.



Hope this helps.

Excellent. This is very likely my issue as well. Will have it changed. :cheers:

Does anyone have the part number for this seal for a 99' Tiptronic?

http://986forum.com/forums/uploads02...1601802443.jpg

3? or (3)?

3


Save money by ordering the ZF part, which is literally the exact same as the Porsche part, for 1/4 of the price.



https://www.pelicanparts.com/More_Info/98639702700M103.htm?pn=986-397-027-00-M103&bt=Y&fs=0&SVSVSI=1048

What is the difference between 3 shaft sealing ring for lid and (3) shaft sealing ring for flange?

I got the porsche part, which is the same as the zf part. 55 bucks. Most expensive o-ring ever.

Sorry to revive an old thread, but I did this to mine today but I noticed some play on the output shaft before and after replacing the seal. The bearings looked good and the part of the shaft where the needle bearings roll is smooth with no ridge.

Did you notice any play on yours? I have about 1/16" or less of side-to-side and top-to-bottom play. How much play, if any, is normal? Does anyone know?

What concerns me is that I didn't find any play on the left (driver's) side.

Diff O ring
 

Great thread! On my 02 S the O-ring (5) on the side cover is leaking along with the axle shaft seal (3).
I'm planning on getting to this over the winter. Am I looking for trouble removing this cover?
My first project with the car was to do the IMS, RMS, mounts, clutch, etc. That was about 10,000 miles ago so the car and I have already been intimate.
I have the 100 things book but it doesn't go into the cover seal and the Haynes doesn't show anything trans related. Oops, can I say trans?
Rob

From what I've seen when I replaced the seal, the cover should be easy to remove. I actually bought the o-ring when I bought the seal just in case mine was leaking, but it wasn't.

While you're there, please check the axe shaft for any play. Mine has some side-to-side and up-and-down play and I'm wondering if it's a common thing.

I'm just curious...

Why would you pay more than twice for a part that is manufactuired by the manufacturer that manufactured the part... for you car... and for Porsche. I mean... Porsche contracted with ZF to manufacturer the part for them, Porsche, then slapping the $30 "P" on the part.

I'm just curious... :rolleyes: