diff set up, too much back lash.

Sat Oct 12, 2013 11:13 pm

Ive put a lsd into a 3.7 that was already in my baur, but theres about 10mm of backlash now. where when the standard spool was in, it was spot on. How do I ajust thebacklash? Ive rebuilt english diffs for donkeys rears when racing F2 and ajustment was on the side gears but on this midcase diff I cant see where to ajust it. Do I reset the pinion higher to meet the crown wheel?, or take out the ally shim that sits inbetween the bearing carrier and casing and put it the other side to take up the slack to move the crown wheel over??? This has got me scratching my bo***cks a bit. Any help or know hlw would be greatly received as I want to fit it in the morning.

Sun Oct 13, 2013 4:18 pm

did you install a matching ratio crownwheel and pinion?

Sun Oct 13, 2013 5:15 pm

I got backlash done on a e36 diff at an engineers, they added a spacer behind the crown wheel and replaced the crush washer, set preload and backlash correctly and raped me without using lube for £200.

Sun Oct 13, 2013 6:15 pm

I believe that the Back lash is set by different size shims behind the crown wheel bearing carriers which in affect moves the crown wheel closer/further away from pinion as you described,

I don't know how you measured the back lash but 10mm seems rather large amount for a shim to take upâaaï¸a

Fri Oct 18, 2013 9:17 pm

Hi all, yes it's a matching 3.7, which has come out the car, and after thinking about it over a millicano and 4silk cut, it's the shims on the bearing carriers that alter the position of the crown wheel to the pinion. Pretty clever but this system dosent allow a bit of gasket sealer both sides of the shim (belt and braces generation). But I'm sure if the rubber seals are in good health then no sealer is required.
Thanks for the relays tho chaps, its back on the bench ready for the morning.

Fri Oct 18, 2013 10:09 pm

Correct backlash is around 1.6mm or little but less so something is wrong alright

The sealer shouldn't make as much difference. Have you the shims fitted on the same side as they were removed from?
What car did you get the LSD unit from or is it new?

The outpus shaft seals and o-rings are cheap, better to replace them while the diff is apart. No sealer required as the o-rings on the output shaft flanges take care of that.