Shark Attack

I feel my 85 has more gear lash than it should. The tranny has 175,000 miles on it. Can this be adjusted in the car?

Thanks
Kyle

BIMMERMIKE

I'm experiencing the same problem, with 125,000 miles on the odometer.
Is it transmission gear lash or differential gears.
Interested to hear what members have to say.

Glenn Evans

Are you both sure that it's not worn CV joints? I'd be surprised if the diff gears had worn noticeably in either of your cars, given their mileage. I presume that neither transmission has been apart, so you will not need to check shim S3 on the pinion shaft inside the transmission.

The procedure for the adjustment of the ring gear and pinion is on pages 39-12 to -29 of the WSM. The primary difficulty you face in trying to adjust the backlash with the transmission in the car is immobilising the pinion gear so that you can measure the backlash accurately. The WSM procedure is to access reverse gear via the transmission top cover plate and pin it, and engage both reverse and fifth gear to lock the pinion shaft in place. If you try to measure backlash with the transmission in one gear alone to fix the pinion, you won't be able to tell what component of the backlash is due to the gears and what is due to the diff ... assuming that the rest of the drivetrain doesn't move at all. You would need to be creative to make something to fit around the diff to pin the pinion gear itself. You would have to be sure that the pinion could not move.

If you solved that problem, you then have to get a dial gauge to bear directly on the teeth of the crown gear, tangentially to their rotation, to measure the backlash. It's hard enough to get the dial gauge plunger past the preceding tooth and aligned correctly with the transmission out of the car. I guess you could do it without removing the fuel tank ... but be prepared to do so. The WSM procedure is to remove the axle flanges and to fit a shaft with an external arm so that the backlash can be measured - relatively easily! - at the correct distance from the crown wheel's centre.

Once you have measured the backlash, you can calculate which shims you need between the case and the side covers on each side of the diff housing. I don't see that removing the side covers and reshimming would be too hard to do with the transmission installed.

The critical thing is to measure the backlash accurately. You cannot afford any movement of the pinion when you are trying to measure about 0.15 to 0.20mm, or you will think that you have excessive backlash when you haven't.

I suspect that if measuring the backlash with the transmission installed were only quite difficult (compared to really #*&@! difficult), Porsche would have written a procedure to do it. I think that, if you really think that you have excessive backlash, you will have to remove the transmission to ensure that you don't reshim incorrectly and make things worse.

Daniel Dudley

The ring and pinion are right behind the back cover. Inspection should be easy.

Glenn Evans

Correct. If you can see obvious damage to the teeth of the ring (crown) gear, or really severe wear, don't bother trying to measure the backlash.

You will have to remove the ring gear and diff to see the pinion. I am pretty sure that you will have to remove the fuel tank for access. In the absence of obvious damage, I doubt that you will see anything to enlighten you.

Mrmerlin

as fas as adjustng goes the answer is possibly, but it will be hard to do, its best to remove the trans and that means removing the rear crossmember, ( this will have to be done anyway if you choose to try to change the shims) as the rear diff cant be removed unless the rear crossmember is out of the way. I would suggest that you drain the oil from the diff and see if it has metal in it.
If it looks clear then i would refill the diff and leave things alone

Shark Attack

I just remembered I have LSD. I am going out tonight and have a look at the CV and TT and see exactly where the slop is at.

BIMMERMIKE

How will you isolate the CV and TT and check for play?

Shark Attack

Ill let you know

Shark Attack

well, my attack may be un-orthodox but here is what I learned. I have about 1/16 turn of lash and its not in the axils.

Now, my problem. I have no idea if i have a problem. It feels like a lot while driving the car. But is it for a car of 1985 MY?