DIFF NOISE

[CHESTNUTXE 7,354]

After rebuilding the b/w diff its smooth and no noise until you take your foot off the gas,then a humming sound,i took it for another run today and found just coasting in neutral there is no noise at all ? any idea's what it could be,all bearings are new.

[SPArKy_Dave 8,895]

Incorrect pinion pre-load would be my first guess.

[CHESTNUTXE 7,354]

too much or less dave ?

[SPArKy_Dave 8,895]

My gut instinct says too much.

Which means a new crush tube.

 

You need to paint the crown wheel teeth, and check the mesh/contact pattern (as well as check for pinion endfloat).

[CHESTNUTXE 7,354]

The guy at the diff shop gave me a 030 shim to put in next to the old crush tube and i tightend it all up

[gerg 10,871]

Sounds like a slight misalignment of teeth, but might bed in eventually. Noise on over-run is better than under power.

 

I know some truck diff places used to lap in gears to get them mated. They'd set up a motorised jig that had the diffs turning slowly in machine compound overnight.

 

When I did up my EA diff, I had a similar outcome to yours but I just left it and forgot all about it.

[Thom 6,654]

Did the ring and pinion come out of the same diff?

[CHESTNUTXE 7,354]

yes its the same diff i have rebuilt 3 times now and im over it ! i did what i was told i did the pinion nut up untill there was no movement then give it a little bit more to nip it up,i got it to 120ft/lbs on the tourque wrench,cant i just back it off a bit ? plus i painted the mustad color paint on the gears and checked the meshing before i sealed it all up it looked good,1/3 off the way from the bottom and in the centre so i put it all together and she is as smooth as when going forward,just wwhhhhhhhhooooooooooo when off the accelerator.

[CHESTNUTXE 7,354]

The diff doctor says probly what gerg said a misalighnment of gears but he wont no until he takes it apart,so im gunna get them to set it up ,then its fixed for good.

[CHESTNUTXE 7,354]

Monday its booked in at the diff shop,he also has good 2nd hand sets of 3.08 and 2.92  ,while its all out again,im thinking of going to 3.08 ?

[gerg 10,871]

Depends on what box ratios you have, what type of driving you mostly do, etc. Won't be much difference between them but I'd go 2.92 myself.

[CHESTNUTXE 7,354]

The clevo pillowblock will be going in soon,its only mild,with fmx,3.27's at presant.

[CHESTNUTXE 7,354]

i got the car back from the diff shop and it is so quiet,i was shittin hard that the bill was gunna be $700 or $900 and the bloke only charged me $220 i was stoked,he said the gear meshing was out and the pinion cup wasnt sitting flush because of me whacking out the old ones and damaging the diff housing,but they said it was a good effort to get it as good as i did under the car 3 times,so all up $220 and $230 for bearings i allready paid for,good lesson learnt just give it to the experts !

[gerg 10,871]

Not a bad rap really for a pro to tell you that. See?.... You did learn something (and hopefully others too)

[CHESTNUTXE 7,354]

i just woke up and cant wait to take the car for a spin,it feels normal now.