BC

Thats whats inscribed on my LSD unit ring gear. Is that total backlash at the teeth or the special VW tool + 80mm out from that diameter - measured there - which by out out radially would increase the total movement.

Page 39-19 in the WSM.

borland

The 0.77mm in the WSM is just an example. You need to use the spec provided with the ring/pinion set you have. Read the manual for how the gear set is marked.

The VW388 just provides an approximation for the specifed backlash. I determined this using the WSM photo, perspective, and 3D measurments to arrive at this conclusion.

You can measure the actual backlash directly from the tooth face (tangential to the ring tooth face) using a dial indicator.

BC

The .76 is the actual number scribed on the ring gear.

borland

The inscription on my 90' S4 is:

7664 E74.98 F0.18

That translates to a....

0.18mm backlash, where the setting range is:

0.13mm - 0.18mm.

I still have a MS Excel spreadsheet that I created for my car when I reset the differential. It's for an automatic, but might help with the manual. PM me with your e-mail address if you interested in a copy.

BC

Thanks alot.

BrenCamp AT Gmail.com

Vilhuer

Check out this old thread:

https://rennlist.com/forums/928-forum/184546-differential-adjusments.html

Imo000

Gear backlash is always measured perpendicular to the ring gear teeth. If you measure it at the middle of the tooth it will be accurate. Sometimes it’s a little difficult to set the dial indicator to sit 90 degrees and at the middle of the face so if you can set is as close to this point the better reading you will get. If the dial indicator is a little off 90, then don’t worry too much about it, cause the inaccuracy will be very minimal (not even worth mentioning). If you are using a different method, you can introduce some unwanted errors into the equation.

I’ve set rear ends this way in several occasions (not in a 928). Also my father has a gear cutting machine shop so I’ve been around gears and the way they are cut/measured for quiet a long time.


I hope this helps!

BC

Well, I noticed a 7 inscribed in another part of the ring gear, so I now know the 7 looking number is a 1, so that makes the backlash .16mm.

I think I need to make sure the new differential bearings are seated properly, as there will not be enough room to make it that small with the current measurements.