Took out my transmission looking for rebuild

Makis · 01-20-2008, 12:34 PM

Decided to take out my transmission that started to be noisy. I thinking in rebuilding it change the bearing etc. While out I check it and by moving thing around it fills pretty good to nothing obvious wrong with it. Is this normal can a noisy transmission be diagnosed like that?

Razorback1980 · Razorback1980's Garage

Noisy back end of car can be a lot of things. Usually best not to take it out until you know where the noise is coming from. You really shouldn't be hearing the transmission while you drive the car. Either that or I am tuning it out. Could be ring and pinion or bad gears or synchros...or something totally different. You should find the problem first, then remove the component.

Makis · 01-21-2008, 12:05 PM

I cannot say for sure but the noise started off about 2-3K ago and slowly i become noisier. The noise can only be one of the following:
gearbox
rear wheel bearings
tire noise
CV joints

Tire noise, wheel bearings or CV joints are highly unlikely as I checked them multiple times. So it has to be the transmission. Apparently is a common problem with S2 transmission the pinion bearings or the diff carrier bearings to need replacing. My box has 170k on it with no previous reconditioning record so I just assume it is faulty. The pinion or any gears or synchros should be OK as I am not hearing any mechanical noise. The noise is bearing type of noise which increases pitch with car speed not engine rpm. (noise the same at 60mph in 4th or 5th gear, or even taking it out of gear and switching off engine)

hpservertech · 01-21-2008, 12:17 PM

Well doesn't that kind of tell you it's not the transmission then if the sound is the same no matter what gear? Kind of a waste to remove it if your not sure that's the problem.

Sounds like the rear wheel bearings. You sure it's not just a wind noise because the rear hatch isn't sealing all the way?

Makis · 01-21-2008, 12:49 PM

The transaxle on the 944 has both the gears and the differential. The noise I am referring to is likely a noise caused by problem in the differential section of the trasnmission.

Razorback1980 · Razorback1980's Garage

You are probably right in thinking it's the differential. The best thing to do first is to get a pan and drain the fluid. If the differential is going, there will probably be some metal in the fluid.

Makis · 01-21-2008, 03:09 PM

Quote:

Originally Posted by Razorback1980

You are probably right in thinking it's the differential. The best thing to do first is to get a pan and drain the fluid. If the differential is going, there will probably be some metal in the fluid.

You write I should do this and have a look. I should also then remove the diff plate and have a look to make sure the crawn and pinion gear is OK. Don't think I can see the bearings or tell their condition though without complete dismantle.

Razorback1980 · Razorback1980's Garage

If the ring and pinion is indeed the problem, there will be metal in the fluid. No way to tell about bearings without taking them out. Never seen bearings fail here though. Usually it's the gears and synchros.

Makis · 01-26-2008, 10:28 AM

I have now removed the inspection cover and here is what I can see.

It looks like the crown and pinion gear is intact, so if it is the gearbox it must be the bearings. There was no big metal pieces in the oil and the oil looked clean and was at the right level. The magnet that is attached on the inspection cover has got hairline metal pieces attracted to it, which I reckon is normal. I will now try to remove the gears out of the main case and have a look at all the bearings. So my question is how can I tell visually which bearing is dead and the possible culprit.

mattdavis11 · 01-26-2008, 11:44 AM

Any possiblilty that the noise you hear might be the torque tube bearings? Might even be the pilot bearing.

Makis · 01-26-2008, 12:37 PM

Well I getting the noise when I take the car of gear and the noise still follows the road speed and not the engine speed. If the noise follows the engine speed when I do this, then I assume the torque tube could be the problem.

I just looked at the inner race of tapper roller bearing that is on the diff side (the one that can be seen in the picture I made) and seen that there is almost 1mm play. Not sure if this normal.

Razorback1980 · Razorback1980's Garage

Sometimes you can see it in the race but I usually have to just feel it. If you put the bearing in the race and put pressure on it while you turn, you can feel a roughness. Often times that is so small, it's hard to see though. This will be a tough problem to find.

machinist · 01-26-2008, 01:37 PM

I just replaced the ring carrier bearings today.
The one on the access plate was in great shape.
The one behind the ring gear (drivers side) was completely shot but still intact.
It had worn so bad that i could almost move the cage around enough to drop the rollers out.
It had also allowed the ring hoghead the wear into the trans. casing on the drivers side.
And to think I was still driving it.
The clue that something was wrong was that the cv driveplates were turning so ellipically that they ate the seals up and it was dripping trans. fluid.
At least now I know another thing to look for when trying out another 944.
Hope this helps.
Todd

Makis · 01-26-2008, 03:27 PM

It sound promising if this is my problem too as the pinion side from what i can see appears to be tight. I will need to remove the gear carrier in order to access the bearing behind the crown wheel. Hope that one will show more evidence of wear as the one in the front is not obvious.

Makis · 01-27-2008, 05:37 AM

I managed to remove the gear carrier and I have now removed the diff. Unfortunately the other diff carrier bearing which I can see now still looks OK normal wear. They all have the same play about 1mm. Also the front pinion bearing looks OK. So I am now not so sure at all what is really wrong with my gearbox. I will probably just replace the diff carrier bearing and put it back on the car and see if anything changes.

Makis · 01-30-2008, 09:33 AM

Trying to remove all the bearings from the main transmission case at the moment. I got stuck on trying to remove the inner bearings for the mainshaft (there are 2). I am trying the inner one and is not moving. I managed to destroy it now and only the outer race is only stuck in the cage. Will some heat help? The right tool might help but there is not much left of that bearing for anything to be able to pull with any reasonable force.

Sacto944 · 02-05-2008, 01:01 AM

Wow. I hope you solve this problem. Like I mentioned before, my car is having similar noise issues.

CV = Good.

Wheel Bearings = Good.

And a shop said they didn't find an issue with the transaxle.

One other culprit I would consider, and in your case as well, is actually the rear hatch...

Makis · 02-05-2008, 02:39 AM

I managed to remove all the bits that I wanted cleanly and now I am waiting to get the parts I ordered to try to assemble it all back together. I will replace everything in the main case ( both differential carrier bearings, two bearings for the input shaft and all the seals, but I will not do the pinion bearing outer race as I am not touching the gear carrier). I am hopeful it will fix the problem but I am getting prepared to try to find another transaxle if everything goes wrong.
If after all this intervention the sound is still the same then I will be very intrigued. Could be the hatch but not sure.

salcaroprese · 02-05-2008, 06:00 AM

Since you said the noise only varies with speed not engine RPM that tells you it has to be from the differential to the wheels. They are the only things that vary constantly with speed and not RPM. Also check anything that is not in a normal spot that may create a wind noise. I would also check the brakes and emergency brake(inside rotor) to make sure nothing small is rubbing and creating that noise. Good luck!

Makis · 02-05-2008, 03:01 PM

OK, I got my parts today and started assembling. Unfortunately one of the bearing they send me is the wrong size. See the picture below:

I put the bearing in but as you can see there is a 2mm gap either size so clearly the outside diameter is smaller. So I need to get back to Porsche to ask them for the correct part. Otherwise I have managed to put in all the other bearings. here is another picture of the diff with the new carrier bearings.