SoCal Driver

The rear stub axles on the early cars are wearing out. The stub axle shaft actually peens or is hammered where the load is on this race. This means that you can get the large nut the correct torque but the bearing is still "loose" on the axle. In 10,000 miles the assembly is loose enough to led the hub rock on the splines of the stub axle. This just cascades to the spacers/seal races.

This causes the outer seal to wear out quickly letting water into the outer bearing accelerating the wear through rusting.

The example race I posted is from a friends car. The whole bearing had rusted and frozen up baking the grease into sludge and causing the inner race to rotate on the axle. The heat and slop cracked the race.

The only way to fix this is to replace the stub axle as well as the bearings and seals. There was some discussion on the "other" board about having the stub axles reconditioned -- welded up and reground.

Don't forget the o-ring around the retaining plate.

Luis de Prat

What's a rear stub axle? Are you referring to the rear wheel shaft? (PN 181.501.263).

SoCal Driver

The part that has splines that has the large nut holding the hub on. Goes through the trailing arm.

The older stub axle has two seperate bearings -- an inner ball bearing and an outer roller bearing.

The later a single outer housing assembly/race with ball bearings at each end.

jeeper31

Is there a way to check this? Any pictures? Sorry, Don't know what the "other" board is.

is this something I can do myself? How difficult is it?

SoCal Driver

Checking the rear bearings on an early 944 (924 and 924S)

Jack up a rear wheel clear of the ground.

Take it out of gear and release the parking brake so the wheel can spin.

Grab the wheel at the sides and rock it back and forth.

Grab the wheel at the top and bottom and rock it back and forth.

If there is any looseness then most likely the bearings are shot and/or the hub is loose on the splines.

Remove the wheel and see if the large cotter keyed nut is loose.

If the nut is loose then the hub, stub axle as well as the bearings are shot.

If the reason you are checking for bad rear bearings is because of a thumping noise or a squeeling noise or a low rumble then it's 99.99% sure that you have bad bearings.

This test holds true for the later bearings.

jeeper31

Haven't had a chance to check anything out but was wondering of there is a chance that this could be something in the tranny. Noise sounds like coming from middle rear of car. Like i stated earlier happens if car is in gear or out of gear and not effected by swerving. It is just a rhythmical thumping that is speed sensitive.

SoCal Driver

Hope it's the bearings! Lot's cheaper than a trans and less trouble.

I would not let it go very long. A dry broken bearing can seize up at the most inopportune time. Think spinning out into on coming traffic.

jeeper31

Also just noticed can't hear noise going in reverse. Could be didn't get car going fast enough.

SoCal Driver

Could be a broken tooth on the ring gear in the trans.

That's expensive.

jeeper31

How expensive? would I hear the sound in all gears or just some? Would the noise stop in reverse?

I think I like the wheel bearing idea better

jeeper31

Lifted car and shook wheel and got some play but seemed like very little. Took wheels off and the large cotter keyed nuts on both sides are tight. Can it still be the bearings?
Spoke to local mechanic who said bearings (which i would do myself becuase repaired at $225 a side) or tranny. Is there any other way to test the bearings? Thinking about just replacing them and seeing if this fixes problem. Should I still do the stub axles?

SoCal Driver

Don't know what you mean by "shook the wheels". I usually pull on the front while pushing on the back of the wheel or the same at the top and bottom. A worn bearing will usually impart some looseness to the wheel.

You can also rotate a wheel that has been raised clear of the ground with one hand on the backing plate and feel a bad bearing.

If you don't feel/hear a bad bearing, either the rumble or the clunking, with one wheel raised and the other still on the ground alternating sides then yes it could be a broken ring gear tooth. One of those things that prior experiance helps.

jeeper31

I shook the wheels the way you described and got a little play.

Can you explain the one wheel at a time thing? When i did his had both wheels raised. Sorry for being dense.

SoCal Driver

When you leave one wheel on the ground and spin the other with the car in gear you are spinning the inners of the differential not the ring and pinion.

You will also feel a bad CV joint with the one wheel method. I've resorted to disconnecting the CV axle at the trailing arm just to isolate the wheel bearings.

When both wheels are off of the ground and the car is out of gear there is a tendency for both wheels to spin when you spin just one. This will spin the ring gear against the pinion and you will hear a broken ring gear tooth.

Just think when you are all through with this and someone gives you a ride in their 944 you can tell them that the wheel bearings or the CV joints or even the trans ring and pinion is/are bad!

jeeper31

Had both wheels up and don't remember hearing anything while I spun the wheel. Didn't try with one wheel on the ground yet. I did manage to start car and let it run while both rear wheels up. Gave it gas and did hear sound but not as loud as when wheels down and car moving