Thread: Recommendations - Rear Diff for IRS

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Hi everyone!

We've reached a point in the project where we can actually start building instead of tearing down.

We're working on just getting a rolling chassis now while spec'ing out a SB Chevy to drop in.

We have an IRS as shown in the attached pic to (hopefully) resuse.

The rear diff pulled out of this car ('97 Eagle Talon) was part of an AWD setup, and was stated by most to not be strong enough for a RWD conversion that might one day reach 500 hp from the initial 350 target.

We were initially thinking a Ford 9inch, however we're open to anything (really, anything!). Cutting and fabbing is no object!

I'm searching the 'net also for others who have done this, so please be patient with me. Essentially my question is:

What would you recommend for a rear-end that needs to handle at most 500hp (altho 350hp is fine if $$ is a factor)? Also, we'd like to reuse the IRS that I've shown in the attached pic. I'm waiting on measurements from my partner's 9inch he's got in his '37 p/u project.

Any and all help/comments appreciated.

Well, if you look at some of the DSM's running 500hp, they have the stock 4-bolt rear diff......So it should be able to take at least 250hp.

Why didn't you look for a Corvette chassis? The '84 and up vette's sell for pretty cheap when theyre smacked-up, and that diff can take 500hp (its a mid-sized Dana I believe).

What car is this going in?

Originally posted by BlueDSM
Well, if you look at some of the DSM's running 500hp, they have the stock 4-bolt rear diff......So it should be able to take at least 250hp.

Why didn't you look for a Corvette chassis? The '84 and up vette's sell for pretty cheap when theyre smacked-up, and that diff can take 500hp (its a mid-sized Dana I believe).

What car is this going in?

It's going in the '97 Talon that crankwalked. I got bored with the car actually.. and it's a project now. I could have rebuilt the 4G63T and moved it around and put another tranny on it, however that's not the project I want to do.

The stock rearend will take the power you are correct.

I"m trying to keep the stock chassis and build an x-frame to tie the two subframes together.

Thanks!

Some of the later T'Birds had 8.8 IRS rears, most were the 8". There's a number of companies making a 9" Ford IRS, Heidt's for one. Check them out.

Originally posted by Dave Severson
Some of the later T'Birds had 8.8 IRS rears, most were the 8". There's a number of companies making a 9" Ford IRS, Heidt's for one. Check them out.

Thanks Dave! I happened across an article from about 7 years ago that spoke of the Tbird IRS/rearend capable of handling over 350hp/340tq.

It will be worth looking into!

84 - 96 Vettes had Dana 36 differentials in the automatics and Dana 44s in the stick cars. The 44 has more beef. C-4 parts make a killer IRS.

I've been running a 84 vett front susp. and a 9" rear for 15 years (good combo)
I have a 86 vette dana 44 ( 44 are from the stick trans) sitting in the garage (ebay $750 and $170 for shipping) I hope to go around corners faster
the drag strip will not allow IRS if you go faster than 11 sec or maybe 12 im not sure what time it is for the 1/4 mile, iam not in to the drags, I want to try auto cross
the vette front was very easy to install
the rear looks like it will be easy also (just not sure what angle to set the 4 links from the rearend to the frame

Hi again gents.. thanks for all the help.

I have a line on a Lincoln Mark VIII rear diff/axle/hubs. My understanding is that this is an 8.8" rear-end also, and most certainly IRS.

This rear-end was used with the 4.6L V8s (280hp) .. if I recall.

Can someone confirm this? I'm still looking myself so any help would be appreciated.

Also looking into the Jag rear-end which was Dana-based.