Porsche Enthusiasts Club Forum

I have traced a slight knocking noise to what appears to be the output bearings in the gearbox. There is 2 or 3mm of out and in play on the bit where the driveshaft bolts onto at the gearbox end, drivers side, and it clicks when you move it in and out. The driveshaft bolts are not loose. The noise is a slight knocking at low speed which manifests itself into a drone at higher speed, seems to go away when turning right. There isn't any play in the passenger side one.

Anyway, what sort of job is replacing the output bearings? Does the box need to come out? Can you get the bearings ok? Do I need a gearbox rebuild?

Car is a 250 turbo with LSD.

Help appreciated!

Stuart

In out play at the driveshaft flanges isn't an issue, any play sideways is an issue. It is possible to DIY but it isn't for the feint hearted. You'll need a manual either on CD or hardcopy.
TBH I reckon it is a knackered CV joint as this is what mine was doing but only once it was really hot.

Hi Jim

The inner CV's are about 6 months old and the outers are a month old, wouldn't imagine it would be them. I could swap the driveshafts round and see if the click moves to the other side?

If it's the gearbox and not the CV's that's making the noise is it still not a concern to keep driving it?

Cheers

Stuart

Ah that is different, unless a new 'un is faulty. It could be output shaft bearings or possibly one of the diff gears. LSDs are noisy anyway but it is worth checking it still works. Jack the car up at the back & turn one wheel forward, the other should turn in the same direction.
Have you checked/changed the oil in the box.

It still works fine! Both wheels spins same way. Changed gearbox oil a few months back.

Stuart

Sounds like take the diff side cage off time And have a nose inside. I assume you have the transmission manual?
If you are really unlucky it could be the crown wheel damaged.

Compared to a wheel bearing I think this is an easier job. Though realistically it's better to do it with the gearbox out! You need a press & a puller. But you don't need to re-shim the diff' as bearings are made to such fine tolerances it should go back just as it came out. So long as your reusing the same one. Mine does not have an LSD & if thats your problem & you want to keep it then it will be expensive. Bearings for the turbo box are more expensive as there an odd size. When inspecting the bearings in yours they should be shiney. What usually happens is that the chrome wears off the balls & they are then rough & start to break up. Not good for the rest of the box. I'm on with mine at the moment so will let you know if it works when finished! My output bearings are shot.