Rear End Sourcing

[Bren]

So I'm trying to source a Posi-traction rear end for a pin drive IRS for the roadster and I can only find the 8.8" non-posi-traction rear ends at the local junk yards. I'm expanding my search, but none of the junk yards will go out to verify that a car they have has posi-traction, which means me traveling to all of these places on the hope that they have something.

Can I get a non-posi-traction rear end and buy new internals to make it positraction? I'm worried that the inside of the pumpkins are not the same on the posi-traction and regular rear ends. Has anyone done this, or am I going to have to keep searching for a rear end that will work?

Thanks

[Gordon Levy]

I can put one together for you

[Bren]

How much does that run?

[Gordon Levy]

Give me a call tomorrow

[CraigS]

The center section is different between solid axle and IRS. The side gears in the IRS need the groove for the axle snap ring to fit into. Other than that swapping the center section is pretty easy as long as you buy a set of spacers and have a dial indicator so you can adjust ring gear free play. If you need to change gears too, that is a whole nother story so concentrate on getting the right ratio. This one says it will fit both solid and irs diffs
http://www.americanmuscle.com/ford-31spline-88-carbondisc.html

[Bren]

The center section is different between solid axle and IRS. The side gears in the IRS need the groove for the axle snap ring to fit into. Other than that swapping the center section is pretty easy as long as you buy a set of spacers and have a dial indicator so you can adjust ring gear free play. If you need to change gears too, that is a whole nother story so concentrate on getting the right ratio. This one says it will fit both solid and irs diffs
http://www.americanmuscle.com/ford-31spline-88-carbondisc.html

So my question is if I can get a non-positrac IRS and get new internals to convert it to a positrac IRS. Is the center section the same?

[Gordon Levy]

It is the same the issue becomes the retaining clips locking in. It will take a little trial and error but it would work fine. I have a mark 8 complete diff ready to be built.

[mcwho]

Try this site:

http://www.car-part.com/

you can search for parts anywhere in the us that u like, in the description area they will sometimes list of its a posi and the ratio also.

[Kpt112]

Bren,

I am in the same boat as you. I have already obtained my Lincoln Mark VIII rear. I am contemplating if I should just replace what I have in the rear with new parts or upgrade to positraction. Anyone that can weigh in to help me make my decision would be appreciated. Positraction is twice as expensive, will it make that much performance difference? I plan to put in a 302 Ford Engine and a tremec T5 5 speed transmission. So many decision. I really appreciated the feedback from the build community.


Thanks
Kevin

[RickGT40]

Bren,
To answer your question directly, you can put a TracLoc differential into an open diff IRS pumpkin. You have to make sure the diff is IRS specific or you will not be able to easily remove the axles form the diff. If you go looking for TracLoc diffs in junk yards you can tell open from posi diffs by the tag on the rear. TracLoc diffs are IDed with a L in the ratio numbers. The Lincoln open diff has 3 08 on the tag while the TracLoc Thunderbird will have 3L27.
I built a rear for my IRS MKIV. I used the Lincoln aluminum case, a T-bird 3.27 TracLoc diff and new bearings and seals.

[aarvig]

I can put one together for you

I agree...contact Gordon Levy. He is the man when it comes to all things Factory Five.

[Bren]

I agree...contact Gordon Levy. He is the man when it comes to all things Factory Five.

Thanks for the advice, guys. But I ended up contacting Gordon and getting my rear end stuff from him. My car is on the road already.

[CHOTIS BILL]

Just for reference for others I also used a Lincoln Mark VIII IRS and put a LSD in it. The only mod required was to increase the length of the splines on the FFR supplied axles with an abrasive disk grinder which took about 10 minutes.

Bill Lomenick