I'm overwhelmed with info and need help! Fox body/rally cross car setup advice needed

OK, so my focus got killed last month.  I needed a winter beater/rallycross car.  I have always wanted a notchback mustang and wanted something funky as well.  We found a rough but serviceable  91 mustang in Vermont.  It is a four-cylinder car, but on a test of muddy roads in vermont, she really seemed to haul the mail.  Honestly, we were in mud to check the car out, so I didn't get to test it as much as I should.  I now find that it doesn't have pos traction or the posi is broken.

I am looking up five lug swaps for the car and now wondering about swapping the rear from another mustang, but I don't how that will work with the 2.3 engine.   I am obviously not looking to be competitive for rallycross, just for fun.

So:  Has anyone swapped a rear end in a fox body?  I cannot find a limited slip for this application, anyone know if there is a limited slip that would fit?

Thanks

No factory 2.3 NA Mustang had a limited slip, sorry. You have a 7.5" rear end with an open differential and likely 3.08 gears.

A common swap is a complete 8.8" rear end from a 5.0 with an automatic, it will have a clutch type limited slip with the same gearing. Manuals had 2.73's usually. You will keep your driveshaft, suspension, brake lines, and everything.

The next step up is an 8.8" from an 87-88 Thunderbird Turbo Coupe, which will be wider, but have a limited slip with a 3.55 (manual) or 3.73 (auto) and disc brakes with the 4-lug pattern. You could then swap on 87-93 5.0 fox Mustang 11" front rotors and a 93 Cobra master cylinder.

5-lug stuff is a whole different conversation.

OK, thanks.  Do you know what year mustang had that rear end?  I'm tempted to run this car as is, it did really well in mud and dirt with studded snow tires.  I'll start shopping for a rear end for this thing.

Thanks

In reply to thedoc :

1987-1993

IMO, keep the 7.5 unless you get a screaming deal.  The 8.8 weighs a lot more and the 2.3 needs all the help it can get.

I am shocked that there are no used Traction-Loks available for the 7.5.  At least, I assume that trac-loks are available in the first place, V8 Fox Mustangs didn't get the 8.8 until 1985-86ish., before that it was all 7.5 all the time.

edit- They were available but I guess hard to find used. You can buy a new clutch pack diff for $320-350, which ain't bad at all for a NEW diff.  Used often go for that much, and then you have to rebuild it.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=7.5+ford+differential&_sacat=6000&LH_TitleDesc=0&LH_BOPIS=1&_osacat=6000&_odkw=7.5+traction+lok&rt=nc

Trac Loks for 7.5s are hatd to find now. The SVO had them but SVO = choo choo money.

Best bet is an ‘86 to ‘98 V8 rear end.  94 plus is wider and has 5 lugs with disc brakes.  Roll those fenders.  I have a 94 GT rear I will sell for $250 disc to disc in Dallas.  

In reply to Knurled. :

So this will bolt in to my rear end?  I was planning on keeping this as stock as possible, just from a cost perspective and the hilarity of this car as a rally crosser.  This is all a great lesson for my son as we have a bigger car fleet than budget, and auto cross season is here.  This also gives me the time to work on this car on days without auto cross.

Thanks for your input,  There is so much info on this that I can't keep it straight!

If you want Traction-Lok for a 7.5 you should look at Ford Ranger  PU's.  I had a '89 with the 3.73 and Traction-Loc behind a 5 sp 2.9 V6.

You will have to pull the diff out and install it in your rear end but it's either that or go with the heavier 8.8 out of a V8 Mustang.

In reply to jimbbski :

So the rear out of the truck is lighter than the mustang?  Is that a bolt in?

In reply to thedoc :

The truck rearend would be a source of a Trac-Lok, not a bolt in assembly.

I didn't know Rangers with the 7.5 could get them.  The only Trac-Lok Rangers that I've seen were 8.8s.  Also some of the most wear I have ever seen, like a quarter unch of end float.

FYI - the differentials in the 7.5's and 8.8's are not bolt-in removable pieces like a 9". You have to disassemble the entire housing and press out the pinion and races. When you move the gears and differential to a new housing, you have to set up the back lash all over again.

I have never seen a factory Trac-Loc in a 7.5. There are aftermarket ones, and you can install them into your housing and gearset, but be prepared to spend far more money than just grabbing an 8.8 from the junkyard.

In reply to Javelin :

why replace gears?  Just pop the diff in and out.

Dont Fox bodies tend to rip the floors to pieces in rallycross use?

In reply to Knurled. :

The OP was wanting more acceleration.

MrChaos said:

Dont Fox bodies tend to rip the floors to pieces in rallycross use?

And autocross, and drag racing, and potholes. Ask me how I know.

I rally crossed a mustang and auto crossed it...oh wait they weren't fox bodies.

I'm on the hunt for a parts mustang

Knurled. said:

In reply to thedoc :

The truck rearend would be a source of a Trac-Lok, not a bolt in assembly.

 

I didn't know Rangers with the 7.5 could get them.  The only Trac-Lok Rangers that I've seen were 8.8s.  Also some of the most wear I have ever seen, like a quarter unch of end float.

The 7.5 was the only rear end installed in the Ranger up until 1989-90. From that point the larger 4.0 V6 got the 8.8 and the 2.3 the 7.5.  So based on the fact that any 7.5 Traction-Loc rear end you find in the junk yard is at least 30 years old it's going to need a rebuild before you use it. The "end float" is simply an indication that the clutches are worn and not the bearings being worn out.

I have a used set of 3:73 gears that may or may not have useful life in them.  $25 plus shipping.