Hi

So my car is a bit ill and is being looked at by the good guys at DMS and Dixon.

I had a 4.44 final drive fitted and after picking the car up I noticed that when the car is warm the rear diff is locking up

I noticed it when pulling away from the kerb with a lot of lock due to the different speeds the wheels at the rear have to turn. Its very pronounced.

Dixon is looking at the car this week and I'm sure will ge to the bottom of it. But i'm curious as to peoples thoughts on what might have caused this?? Any one else had the diff locking before?

As the diff internals werent disturbed I'm not sure Could it be some metal shavings from the new gearset breaking in getting in to the LSD perhaps?

The current plan is to change the diff fluid and put in some friction modifier, hopefully that will sort it.

I'm really worried though obviously, I drove the car a good 70 odd miles before noticing the issues and getting it back in. I also have a track day 11th March. I'm thinking it might be better to cancel it if I can? I'm worried about it locking up at speed whilst on track, especially with the high temps it will be running at and perhaps the gearsstill breaking in... Think this would be a good idea?

 

Why put in friction modifier? That's a bodge if ever I heard one.

The diff worked before, it should work again without any special fluids.

Got to be to do with the lash setting between pinion and ring - probably too close.

Who fitted the kit for you?

 

Dixon, so it was in safe hands. Friction modifier is what's being recommended.

Could lash cause this then? I know little about gears. They did come with a lash setting value in the box.

 

EDIT

I disagree, but you are entitled to believe that.

 

mmm, Ive not heard anthing like that and to date service has been great, but thanks for the views.

Regarding the back lash, this is something that could cause the diff to lock up you think then? Could you explain how? From diagrams I see the final gear simply bolts to the diff unit. I'm interested to understand to make sure it gets rectified properly, if I have a blown diff a few months down the line I'm not going to be a happy chap.

 

Well, i'm using a process of elimination - systematic fault cause.

I am not an expert in differentials BTW.

My best guess is...

Actually, i'll PM you

 

Fitting a 4.44 does involve stripping the whole diff down, and re-shimming and backlashing. It's quite tricky and needs dial indicators and precise shim calculation. It will not be shavings.

 

We are looking at it now and will get to the end of it to sort this out no matter what.

Straight line run is fine and is only start locking up when its warmed up. When its cold you can do whatever and it will make no noise and run smooth.

Backlash has been set to the recommened setting from the manufacture, we might take it out and recheck the backlash if needed and inspect the diff unit.

Will update how we get on with this later.

 

Sorry perhaps I was getting my wording wrong. The diff casing needs to be openeded, but the torsen diff itself doesn't need to be opened I understand, the final drive attaches around it?

As it happens only when the car has warmed up could some metal be expanding putting pressure on the diff unit internals? Possibly due to the final drive gear being around the diff and still breaking in? Could it be the backlash is out causing excessive heat maybe?

 

You should replace shims etc for peice of mind,they were in mine. My diff was done around 4years ago and is still going strong.