Diff guru diagnosis

Sun Jun 14, 2015 2:12 pm

Hi guys , I recently purchased a diff on here for my car , it's a medium case 3:91 torsen LSD , it's been on about a month now and I've noticed I'm hearing a clunking noise in between throttle apllication and lift , I've had the car on a ramp to investigate , the guibo looks fine as does the joint at the diff end of the prop .. The noise sounds internal , almost behind the rear case . If I stand under the diff with a wheel in either hand and move it forward and backwards I can hear a metal clonk/dong like sound . Also one of the output shaft at the rear of the diff has play in it , should that be the case ? I've spoke to a guy and he said the diff should naturally have some slight play but I'm not convinced .. Any help wod be great . Cheers guys

Mon Jun 15, 2015 10:01 am

The diff will have play in it because its full of gears compared to a clutch LSD, the noise will be the CV joint

Mon Jun 15, 2015 1:12 pm

Output cups on my torsen have a little slack that's the splines of the cup to the inner of the diff, 1st gear clunk is pretty common on z3s that had the torsen.

It comes down to lots of small tolerances stacking up. fraction in the shaft splines, fraction in the cup splines, a fraction on each of the gears inside, a tiny bit in the CWP a tiny bit in the prop ujs a tiny bit in the prop splines etc, etc.

Unless it is really bad I would not worry about it, if it is quite bad then check out your propshaft UJs, if they are dry they wear fast and become loose.
It is possible to grease them with a hypodermic needle and some thinned molyslip.

Mon Jun 15, 2015 5:31 pm

Cheers guys .. It's not really bad just slight play and I'm absoloutly anal about stuff like that .. If it's loose , rattles , creaks or leaks i will find it !!!

Mon Jun 15, 2015 7:33 pm

I know what you mean, I was not happy with the slack in mine until I had spoken to a few people about it (Gareth included) and found it was perfectly normal for the torsens.

Mon Jun 15, 2015 10:18 pm

Thanks dude , I'm Gonna refresh my entire rear end and prop to eliminate any play that's amplifying the diff movement .

Mon Jun 15, 2015 11:41 pm

Actually both of the above are very good points.

When ever I have a subframe out I tend to add a plate to the top of the rear part now. Seen a few crack even with stock engines.

Fri Jun 19, 2015 3:14 pm

Mine used to clunk between gear changes, turned out the 4 bolts on top of diff housing worked loose. Try it!

Sat Jun 20, 2015 11:02 am

Was on my old car. Diff was on and off quite regular changing cwp's and changing ramp angles/diff pre loads etc. Tightened it up and was all good then! Cheers