I have a 3.9 non-lsd diff and wanna swap for a TII 4.10 LSD diff. I know I have to switch both output shafts and axles and gasket. Do I also have to switch the rear casing that mounts to the car or are they all the same ?

I have an S5 GTU was automatic n/a now is a Bridgeport S4 turbo, S5 TII 5spd tranny. I need an LSD to complete the conversion. And the LSD I plan to buy is an S4 clutch type. Thanks.

 

Are you sure yours is not an LSD? The GTU's came stock with an LSD. It could just be worn out and need a rebuild.

I am also trying to figure out i my car has an LSD or not, it is not easy. i think i am going to have to open the diff to find out.

 

Just swap the whole diff to save headaches. This was discussed not long ago.

To tell if you have a lsd, lift the rear of the car, spin one side, and if opposite side spins the same direction, u got lsd. opposite =open

 

Yeah, i know of this test, my test just came up funny. On my NA car the other tire spun the other way easy, open diff.

But on the parts car the other wheel didn't spin at all.

Whats that mean?

 

Hold the driveshaft and try it again

 

Driveshaft was held for the test. When the other one didn't spin i thought that might be the problem, but i held the driveshaft and still, spin 1 wheel and the other does nothing.

 

Yes I'm sure it's a GTU and the 3.9 diff ratio's were non-lsd and only on automatic tranny powertrain.

 

I can save myself a headache and a hole in my wallet knowing that I dont have to swap the rear casing that the diff bolts onto.

 

As far as i know the TII diffs are 1" bigger then the non turbo diffs, so you would need to get the whole diff from a TII to use it's LSD.

Also, the driveshaft and halfshafts would also need ot be changed.