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Posted by: pek771 Aug 17 2022, 03:25 PM

I am putting in a Quaife TBD. I pulled the shims/spacers off the old differential. and did not note which went where. One is around .010" thicker than the other. Was this how they set up ring and pinions back in the old days? Is there a spec for this somewhere?

Posted by: ClayPerrine Aug 17 2022, 03:28 PM

Paging Dr. Evil. Dr. Evil you are wanted in surgery....

@drevil

Posted by: stownsen914 Aug 17 2022, 03:38 PM

When you change differentials, the backlash and preload need to be reset so the ring gear meshes correctly with the pinion. Since you are changing, the shims may be different than what was needed for your old differential. Dr. Evil can point you in the right direction or just do the work for you. Not necessarily complicated, but precise and requiring some special tools.

Posted by: pek771 Aug 17 2022, 07:07 PM

I found this on here.
http://www.914world.com/bbs2/index.php?showtopic=205796&hl=trans

Very interesting in that he also feels that the lash on the R&P is overlooked. I'm putting in this sort of differential so as to maximize the traction ability at lower speeds. It as fairly apparent I will need some sort of tooling for this, which I can fab up on my lathe. The old differential and the Quaife are machined the same, as far as critical distances across the case go.

BTW, the staple answer is to use the same gaskets the transaxle had from the factory, never mind any shims on the differential. I think I am going to have to trial and error it until I am happy with the pattern and then do some math to configure the Quaife.

Posted by: pek771 Aug 17 2022, 07:15 PM

Part of the issue here is that the transaxle was rebuilt by someone maybe 40 years ago. A-F-M-S-X. I replaced the X with a ZD stock 5th gear. So, the spacers which maybe were set up correctly are now mixed up, which has precipitated this entire train of thought.

Posted by: mgphoto Aug 18 2022, 08:56 AM

The “thinner” shim is usually on the ring gear side.

Also when working with these shims it is best to use metric measurements, the math seems easier whereas engines thousandths is preferred.

Pinion depth is set using shims on the pinion shaft than micro adjusted using gaskets between the case and the intermediate plate. If you removed these shims, you should be able to replace them and use the same thickness gasket for the pinion depth.

The backlash is what needs to be set when changing differentials.
The new differential will be a different size requiring different size spacers. The spacers vary by .1 mm with an additional shim at .05 mm.
Measurements start at .1 mm larger on the ring gear side and adjusted by changing spacers to get the correct backlash.

Posted by: brant Aug 18 2022, 09:57 AM

I agree... you may need to measure the side play and the shims mentioned in your thread to fit the new diff.

but the ring and pinion are set using back lash in the forward/rear directions.
the factory tool is expensive, and its a complicated process when changing the spool.

others have taken a spare trans case and cut a window in it in the past... to allow measurements of backlash. or the factory method.

usually best preformed by a professional with experience.

brant

Posted by: mgphoto Aug 18 2022, 10:59 AM

This is the tool to set pinion depth, the procedure is in the factory manual but also read the Sportomatic section as it is much more detailed in the procedure description although the numbers are different.







After the pinion depth is set the backlash needs to be set.

Spacers under the carrier bearings need to be replaced as necessary to position the ring gear in the correct position. The difficult part is not destroying the bearing cages pulling them off and replacing the spacers.









The backlash is measured with this type of rig.







The results can be very satisfying.

Posted by: pek771 Aug 18 2022, 01:36 PM

Wow, @http://www.914world.com/bbs2/index.php?showuser=10225 , nice setup. I ended up simply making a go-no-go gauge with my old open differential. I cleaned off the R&P really well, and put some R&P schmutz on the mating surfaces. So, I set it up with the thinner spacer on the fixed cover side, and the thicker one on the removable side cover side, and it was riding almost identically to where it was before. I called it good, and put it back together.