Tell me about LSD diffs and their oil....

[Muncie]

My new daily A vx commodore has a slight low speed shudder when you turn sharply u turns turning out of driveways etc. The lsd certainly works as this things tail happy im going thru all the fluids and engine and trans are done but im getting conflicting info on needing an additive synthetic semi sythetic oils etc whats the general concensus you mechanic guys out there what do i need to settle it down. Its a mild shudder it sounds like when you push your thumb across a clean plate while doing the dishes to me it might be the wrong oil in there so best dump it and rule it out.

[johnnyfive]

Ask your dealer for the expensive additive in a little bottle, chuck it in with new fluid if you're feeling flash.

 

Go do some slow figure 8's (not skids) in each direction a few times. 

 

Happy days. 

[thegreatestben]

Go to nearest Holden Dealership and buy AC Delco oem stuff?

 

Cam could be worth a PM if you aren't friendly with the local dealer.

[Muncie]

Does my fault sound like tired oil or no additive? Hate to poor pricy additives into a rooted diff. Ive only played with nissan stuff r200's before.

[Roman]

Firstly, what type of LSD is it? Different oil might fix shudder in one type but not another.

 

My experiences with a plate type.

Getting shudder means the plates are grabbing too much and so the tire skips instead. As the diff stays locked.
Unless there's grooves or something on the plates causing it to bind or something, but you wont know that without pulling it apart.

In my experience:
 

Used some type of LSD oil available from Repco and had a mad shudder.

 

Tried tried the redline equivilent and it was much better, even though same oil grade...  but shudder still there.

 

Then I added a bottle of Cusco friction modifier oil (you can get this from BNT) and it was night and day difference. Still shuddered though!

 

So ended up disassembling LSD and reducing preload and changed plate order etc, and this totally transformed how the car behaved.

Then went back to the original (cheaper) type of oil with no modifier in it, and life has been good ever since.

 

TL;DR: Changing oil made some amount of difference, but didnt make the issue go away.

 

[Roman]

Does my fault sound like tired oil or no additive? Hate to poor pricy additives into a rooted diff. Ive only played with nissan stuff r200's before.

An oil change could make all of the difference, if it's been in there forever... Worth a try as your only other option is dissasembly.

[mint16]

The factory Holden diffs for that model are cone-type LSD and they are poose.

From my experience, if theres a shudder, its terminal. Worn cone surfaces.

There were plenty of occasions like this when working for a Holden dealership, especially with cop cars under 100km on the clock.

Using the GM additive did not reduce the shudder, the only fix was to fit another diff (used) and hope for the best that it didnt have the same issue.

[Muncie]

Bummer its bearable at present so will give it an oil change hoping for the best and keep an eye out for another diff. Its only low load it does it so not noticed 95% of my driving.