Rebuilt S80 Gearbox Rattle


NIcad7

NIcad7

EG6
Joined
Nov 19, 2011
Messages
359
Hoping someone who has handled gearboxes can help here.

Had this S80 rebuilt, however when I move it around something is rattling inside. I don't know if it's a 'normal' rattle or not. Everything feels fine, turns smooth etc. Was hoping to put this into the car this weekend!

Please have a look at the video below and tell me if that's normal or not :please:

https://www.youtube.com/watch?v=CjKMZpxWAjY&list=UUNyfLD4bUE2i6AtEIybubdg
 
Last edited:
No that's not normal. Had a few s4c LSD boxes off and one apart to fit a new LSD and none of them made this noise.
Something is moving around in there. Who rebuilt it?
 
Uuuuuggggghhhhh.

I don't know who rebuilt it, although I swapped the casing a while a go so it's most likely my fault. It feels like its the shaft in between the diff and input shaft (whatever that's called?). I'll pull it apart tomorrow and have a look.
 
when you swapped the case did you make sure the shaft was secured again with the circlip. could also be a bearing missing from the end of the shaft during the case swap causing the noise?
 
elchunk said:
when you swapped the case did you make sure the shaft was secured again with the circlip. could also be a bearing missing from the end of the shaft during the case swap causing the noise?
Click to expand...

The casing doesn't go back on if the shaft hasn't sat the the circlip iirc? could have missed it out completely I suppose? Would make that sort of noise.
Needs to come apart for sure.
 
jesse888 said:
The casing doesn't go back on if the shaft hasn't sat the the circlip iirc? could have missed it out completely I suppose? Would make that sort of noise.
Needs to come apart for sure.
Click to expand...

normally have to turn the box on the side for the shaft to seat with the circlip. to me it sounds like when he was swapping the cases one of the bearings was left out.
 
Circlip is there, seated nicely with a clunk when it went back together.

I wonder if a bearing is too small somehow? As its side to side movement considering the orientation of the shafts.

Anyways Ive got tomorrow off so I'll pull it apart and compare it to some diagrams see if something is missing.

Thanks for the help so far :)
 
Ok so pulled the box apart quickly as I'm impatient ;)

At first I thought it was the diff. You'll see in the video below, with the diff and shaft in together moving the diff side to side causes the noise. With the diff in alone it sounds perfect.

So it sounds like the shaft right? But it sits perfectly snug in the bearing. Going to pull the diff out and have a look now...

https://www.youtube.com/watch?v=2Ocy2EdIp20&list=UUNyfLD4bUE2i6AtEIybubdg
 
Last edited:
Are the diff bearing outer races a tight fit in the casing? I've come across 2 different styles off diff bearing in the past, taper and deep groove type I think
 
Yup, the diff bearings are pretty tight. If the diff doesn't go in perfectly square it will get stuck!

Just put it all back together, rattle is still there. It's more of a knock I guess.

Can't work it out :((
 
Should also add it's got a KAAZ plated diff in there although I doubt that matters much.

It's just feels as though the diff is floating in there if that makes sense? Like when I put the shaft in it pulls the diff up slightly. I don't know it's hard to explain.

I'm almost tempted to put in on the car this weekend and see what happens :D
 
Sounds like your missing a shim or maybe have a bearing fitted back to front or something like that, I wouldn't fit it, you will only have to pull it out again
 
As mentioned, when fitting new diff bearings to an LSD the bearings should come with a shim each. This shim should go between the diff and the bearing is then pressed over it.

Also when fitting a new diff to a casing you need to measure the gap between the bearing face and the top casing when its fitted. you measure this with the driveshaft seal out and use feeler gauges. iirc the gap should be between 0.01thou and 0.1thou

If the diff is not shimmed properly it will move back and forward possibly causing your rattle
 
There is a shim with the diff, but its between the casing and the diff bearing, I'm guessing that should have been put in between the diff and the bearing like you say. There is only one on one side and nothing on the other though.

The diff isn't new, i bought a '96 spec box with a KAAZ diff and 4.7 FD, rebuilt but the casing mount had snapped off. So I bought a new casing to swap it into.

I assumed everything would simply swap straight across, but clearly not!
 
I'm going to pull it apart again in a minute. Then bolt it back up with just the diff in to see if it's still knocking. Failing that I'll try the countershaft. Will hopefully narrow it down :)
 
Well individually, the diff and countershaft make no noise or movement at all.

I'll try them together now.
 
Yes there should be a shim between the top casing and the top of the bearing, when you change casings or change the diff the clearance between the casing shim and diff bearing should be checked and changed as required

When fitting the normal non-tapered bearings anyway there is usually a small shim supplied with each bearing to go onto the diff before pressing the bearing on, I guess this is to provide a bit of clearance between the diff housing and the bottom face of the bearing
 
Yep, just makes the noise when the counter shaft and diff are together. Wrong size shim on the diff maybe?

It seems to be the meshing of the gears between the diff and countershaft. As though there is a slight gap between the teeth causing the knocking when the teeth hit each other.


Hmmmm, it has a KAAZ Diff and a KAAZ FD. But I wonder is this is just an S80 countershaft instead of a KAAZ one which would have been originally supplied. Perhaps the countershaft FD gear is slightly smaller on an S80 than a KAAZ??
 
You must log in or register to reply here.
Back
Top