Vilhuer

As WSM gives +/- limit for backlash adjustment I would try to move a little inside these limits by changing shims before changing ring and pinion. Even this kind of minor change could help.

Jim bailey - 928 International

Actually Russel I was talking about ANOTHER customer ! I do show the O-rings in stock on OUR shelf for like $9 each ....shipping is however $$$

DSC928

Oh sorry.....send him my condolences!

Schocki

If the noise stays after adjustment and the ring and pinion look OK....
I'm going to turn the volume up on the radio that's it.
The noise came with the car when I bought it. But it never really bothered me in TX (took the highway to work). Different story right now in Germany. I'm driving the car about 2 times a week.

The car is going into storage at the end of Setptember and I have all winter to take a look at it.
I also found an aftermarket source in Germany that sells all kinds of O-rings, you just need to know the size...

Vilhuer

PET and WSM do not list o-ring size but I do have manual trans kit and few side covers on hand. Might have another partial kit with unneeded rings too.

Schocki

Not for the 92 GTS, but for the 91 model

If I can't get the rings from a supplier in Germany I might contact you Erkka.

Schocki

Removed the cover of the differential housing today. To access the differential I removed the heat shield on the gas tank and dropped the rear portion of the exhaust (partially). I fabricated the pinion holder to according to the WSM and measured the backlash.

According to the numbers on the ring the backlash should be 0.1mm. I measured it multiple times and the most accurate value was 0.25mm. Way beyond specification. Adjustement itself was not that bad. Removed the CV joints on the tranny side and removed the CV flange. The carrier bearing housing is held in place by a couple of 13mm bolts. When the housing comes of the O-Ring becomes visible and the washers that adjust the bearing pre-load and the backlash.

O-Ring size: Inner diameter 110mm (Carrier bearing holder diameter is 115mm and the groove depth is 2.4mm) with an o-ring thickness of about 3.5mm should be fine. I left my o-rings in place they still looked good and where in good shape. Hopefully everything stays dry...

Since my differential had to move to the pinion (towards the passenger side), I had to remove one washer. One on the driver side was exactly 0.15mm, so I was lucky . The removed washer was placed later on the passenger side carrier bearing housing. This assured that the pre-load remained the same.

Took me 3 hours today to get this far. Backlash is now back at the factory value. Assembly in reverse order will be done tomorrow.

BTW
The wear pattern on the ring was excellent and the oil looked just fine. More after the test drive....

Bill Ball

Can't wait to hear the result...or NOT hear it, in this case. Hope it does the trick.

borland

Per the WSM:

“Backlash required is stamped on ring gear.
Adjusted backlash value could be less by
0.05 mm, but must never be greater than the
stamped value.”

“Check backlash at four places on periphery.
turning ring gear by 90” each time.
Measurements must not deviate from each
other by more than 0.05 mm.”

My gears set inscription is:

7664 E74.98 F0.18

So, from the inscription on my car, the backlash is 0.18mm. And the permissible adjusted backlash, per the WSM, is in the range of 0.13mm – 0.18mm.

I found a combination of shims that resulted in an average backlash setting of 0.14mm while still maintaining the proper bearing preload.

Schocki

Gear set inscription is: F75.00 F0.10

Thanks for the info borland. Did the measurements already as described by you. My backlash was definitely way beyond tolerance (0.25mm). Haven't measured it again yet after moving the shims.
But it should be just fine.

Before the measurements there was a "feelable" play within the gears. This is now gone... we'll see

Assembly after church service today.

dr bob

I'm sure you know this, but just a reminder for others thinking about this task-- Be sure to measure that you actually have the correct clearance. There needs to be enough room for the oil film between the gear faces at all times.

Schocki

Project completed

The backlash measures now between 0.07 and 0.08 all the way around (checked every 90 degrees).
The noise went down about 50% and is what I expected. The good news is that the speed band where the noise starts end ends is little narrower. Starts a little later and eds sooner, but nothing significant.

So question is was it worth it? Yes and no.

No: The noise did not disappear completely, but was improved.

Yes: Looking inside the differential housing and finding nothing wrong was definitely worth the time. There were NO metal deposits of any kind on the magnetic plug. Cleaning out the housing with a clean rack did not show any wear or metal pieces. The car is good for another 120k the way the wear pattern looked.

Below a couple of pictures of the self made tool and the tool in action.

Bill Ball

Schocki

Don't want to fire up an old threat but I have to ask you guys about this:

A guy in the Netherlands says that his inside gears in the differntial housing have a lot of play. Aybody has some experience whith the adjustment of the inside gears.

Bill Ball

AFAIK, there is no "adjustment" for those gears.

My open diff has always allowed more than 3/4'' of play measured at the rim of the rear wheels with an audible click if I rotate the wheel back and forth. I checked other 928s and didn't find as much play or any click.

When I investigated this, I found the pinion/ring backlash to be within spec but I observed the small gears "rocking" on there shaft. I suspected their bearings or inside gear surface or shaft had worn. That was probably 6 years and 80K miles ago. Nothing has changed in the interim. I had planned to replace either the whole inner gear assembly or the complete diff, but since it has been totally stable, I have just left it alone. Unless your buddy has some performance issue related to the small gears, he might just watch and wait as I have done. I do have a spare open diff as well a spare small gear assembly (gears, shaft, bearings) sitting on the shelf if needed.