What's the highest amount of torque your modified FD rear end was able to handle? What did you have to do to it? How many drag passes were you able to get in before it needed to be rebuilt? What was the weight of your FD?

BTW: My last FD had a Kaaz LSD and and chromoly axles, so I already know about that. I am looking for setups on cars with 700+ ft lbs of torque.

 

My car made 381 rwtq last year on the dyno, it weighs 2770#. I drove 2 years with the stock 4.10/torsen and just swapped to a 3.90/s4 t2 clutch diff. Haven't broken anything yet, if you can avoid wheelhop the mazda stuff can handle quite a bit.

 

Noone running this kind of power or what?

 

What's the best step to take to stay away form wheelhop? I'm assuming all poly bushings, will changing spring rates have any effect?

 

http://www.kgparts.com/brace.htm

 

Good question and thanks for the answer also!

 

a friend that races pro modified makes 835 hp and only 585 torque, so i dont think you will find street fd much over 400 tq. my friend runs modular ford 9 in.

 

I think he's doing the v8 thing in his FD.

 

Are you looking to keep an IRS setup, or go with a solid axle?

If you want to stay with an IRS, go with an 8.8 Cobra rear end. Jimlab is currently making the cradles to do this, but I hope to soon be taking this over!

You might also try PM'ing Lupe on the forum. He swapped in a Ford 8.8 solid axle.

Your only other option is the same that you've already posted...Kaaz LSD, and chromoly axles.

-Alex

 

I already have someone that can put a built 12 bolt in with a tubbed rear, but I want to know what I can do to avoid that this year and then have the 12 bolt put in for next year. I know I will probably blow the rear regardless, but I want to at least get 5 good passes.

The engine in my car last year came out of a car putting out 700+ ft lbs of torque, and I am going to top that this year.

 

Gurumotorsports.com

Dont know the torque rating on it, but they said its one of the best torsen diff's you can buy!

 

Will that be good for a drag only application though?

 

clutch type are better than torsen type for drag racing. KAAZ is probably the best you are going to get in the stock FD rear.

 

From all the research I have done, the S4 TII clutch type diff is just as stout and costs quite a bit less. Not to mention it is a more streetable setup too (no clunks, no crazy breakin, no special fluid needed).

 

I don't mind the clunks, I got use to that quick. I just want to have the best parts possible in a stock FD rear end to avoid a 12 bolt this year.

 

Hey Dan, I didn't know you were on this forum!

*Back to Topic*
I'm sure there isn't too many FI LS1/2/6 cars here making 700 ft/lbs...

 

My $2 cents on this topic...

DON'T go with the Cobra IRS 8.8 setup....That would be a big mistake if you have a car with 700ft lbs of torque...

 

True, they are the weak link with stock Cobra's and are awful for drag racing.

 

It looks like I will just be going with a built 12-bolt. Thanks for all the help.