View Full Version : Differential Rebuild or buy new?

Tbirdsc Colonel
05-30-2006, 01:53 PM
I just got a 99 cobra diff. and I was debaiting if I should just rebuild mine or go with a fard racing or an auburn Pro. I have about 102k on my 95 engine rebuild less than 2k ago and thats really the only thing I need to replace, So I figured Since its going to be out anyway

Once Dave D. Finishes my heads ill be in the range of 350 rwhp

David Neibert
05-30-2006, 02:03 PM
Do you have the whole Cobra pumpkin or just the diff ?


Tbirdsc Colonel
05-30-2006, 02:52 PM
Just the alum diff but I might still be able to get a hold of the internals but I did not think that would work? I know the 99 have 28 splines but I thought something was differant?

David Neibert
05-30-2006, 04:33 PM
I'm not sure I understand what your trying to accomplish. What are you planning to do with the empty Cobra diff case ? Did you get the aluminum case just to save some weight...are you planning to transfer all the internal parts from your existing pumpkin ?

Is the diff you have in the car now a traction loc ? Are you installing gears ?


05-30-2006, 04:44 PM
I have all of the tools to rebuild these diff correctly and the know how to make them last. I can add an extra friction to a stock TL carrier as well.

Tbirdsc Colonel
05-30-2006, 09:08 PM
Im sorry dave its just me not explainging I got the empty diff to save weight but since its out and I have 100k on mine I thought it would be nice to beef it up a little. I have the stock 95 rear with the exception I do i have 3.27 gears but thats it everything else inside is stock and never been replaced. Just kind of hoping to get opinions on if its worth it to beef up with the FMR, auburn pro or just rebuilt the stock.

05-30-2006, 10:05 PM
You mention that you have a stock 95 rear end (differential). You don't say if you have a Trac-Loc or Open diff. Both were "stock" in '95.

With the kind of hp/TQ that you'll have, you should probably go with something stronger than a Trac-Loc, in your new alum. case. If you do in fact have a Trac-Loc & want to keep/rebuild it, the alt. stacking method looks like it will handle more TQ than the Ford stacking method.

I will never recommend a Regular Auburn Cone, which I have. I can feel it slip about 1.5 revolutions before it grabes. The Auburn PRO has more bias pressure that the regular, & is more suited for SC's.

When I replace my Auburn Cone, It'll be with a Detroit Tru-Trac. The Tru-Trac is a Worm/Wheel design (clutchless). Allows full differentialization around corners, but locks solid when you race. It's suppose to handle at least 500 hp!!!!!

The OEM 8.8" Trac-Loc in SC's is a Medium Duty unit. I tore up 2 of'em (both with 30K mi. on them), before I put the (regular) Auburn Cone in.


David Neibert
05-31-2006, 02:11 PM
I think your in for a ton of work for very little weight savings. If the pumpkin you already have is a trac loc which I assume it is, I think your better off rebuilding the clutch packs using the alternate stacking method and larger "S" spring that Mark mentioned.

If you swap housings then you have to do a bunch of other stuff to get the correct preload and gear enguagement/backlash ect...ect....


PS: I'm using the stock trac loc in my 91, and I have an Auburn Pro in the 93 and both feel the same to me.

06-01-2006, 08:14 AM
If your car has the traction control button (auto) it isnt traction loc and you would need a whole new differential. The 99 cobra internals all work fine.

As Alan has said you can rebuild the diff (if it sa traclock ) with more disks and a tighter spring for even better performance.

So #1 do you even have a posi?
#2 If no get those stock 99 cobra internals
#3 Get it rebuilt..Might as well
#4 No need for an Auburn

I wouldnt even bother however just swapping everything from yoru iron carrier to teh aluminum..Get the aluminum one done then install complete,,Swap in swap out

Just my two cents