Race Engine Forum UK

Hello all, my name is Liam and new to this forum.
I'm in the process of rebuilding my gearbox and installing a Quaife LSD. Now being at a stage where I can’t continue without some guidance with regard to differential bearing pre-load.
I have contacted Quaife to see if they had the information I needed. They said that there diff is a direct replacement of the factory diff and would need fitting to factory specification, information they did not have.
I have the following information from the Fiat workshop manual: 1, Differential bearings not pre-loaded = 0.12mm. 2, Differential bearings pre-loaded = 0.08mm. How would one interpret this?
Any help greatly appreciated.
Thanks
Liam

Hello Liam,

If I remember correctly, when I did a similar installation, I used the option 1 (Differential bearings not pre-loaded = 0.12mm) which is much easier than option 2.

This option 1 means that you will adjust the differential statically without any load.
First I used the original shim and a feeler gauge to find out the gap between the differential body and the cover.
Then, I used other shims to slightly modify the height between the differential body and the cover in order to get a gap lower or equal to 0.12.

For information, the shims are provided by the Fiat dealer and are designed from 1.70 to 2.60 mm (step=0.05).
In the workshop manual, they advice to use a dial gauge, but I think it is easier to use the feeler gauge.

Regards,
Daniel

Daniel,

Thank you for your response. Following my own research, I was planning on measuring in the same way that you describe. I have been informed by Frank from Avanti to pre-load by 0.15? Does anyone have view on this?
From the Fiat specs of 0.12/0.08. Are they suggesting the pre-load can be anywhere between these two numbers?
Forgot to mention previously, torque setting for the box rebuild would be greatly appreciated too.

Thanks

Liam

Thanks to Daniel on this one.

CAN ANYONE ELSE ADVISE PLEASE?

Thanks,

GC

Thanks for all your help on this Guy, and thank you again Daniel.

Right! I'm going for a pre-load spec of 0.12mm (Fiat recommend .08 to .12 and Avanti .15), so anywhere between .08 and .15 and ill be happy.
I have found a machine shop that can make the shims from mild steel. Each shim will be cut from a 75mm bar and then surface ground to the specified thickness. Due to a lack of proper measuring equipment I'm having three shims made - 2.57/2.60/2.63. Fingers crossed one of them will be right.

Liam

Hi!

Hopefully You will find the "perfect" shim, if You do not - no reason for panic. You have another way to make it fit.

My technical english is not good: The differential cover that holds the differential bearing in place (no idea of what its called) is made of aluminium. The mating surface might be ground down the couple of microns to make a slightly big shim fit like a glove;-) Do it on sandpaper on a flat surface with frequent checks.

This cover or plate holds the differential bearing in place - and is the item I am talking of: (It looks the same on Your UTurbo gearbox)


Regarding the clearance - I have just a tiny little bit of experience. I never use measurements as I have found no practical way to do it properly - we are talking small clearances here.

From what I have understood - and practiced with no ill effects:

- If all the diffbearings are new: Find a shim/grind cover so the diff can be turned with VERY VERY little effort and NO play.
- If reusing good diffbearings: Find a shim/grind cover so the diff SPINS FREELY with MINIMAL play.

I am on very thin ice with this one, and am prepared get butchered for giving this advice;-)

I would contact URBANCAMO on this question....... he will most probably know.


Remi

Hi Remi,

Thank you for your help. I have now found the ''Perfect'' shim in the form of 2.60mm shim I had made by a machine shop. The box is now back together and in the car. I did have a moment where the three springs and roller bearings went flying but luckily found them (amazingly). My first gearbox experience and it went well, not as scary as I thought it was going to be.

Here are some photos of the shims and how I measured the pre-load.

Liam