I want to swap a 1994 Firebird differential into my 1981 Elky. I realize that the flange to flange dimension is too long, but if I shorten the housing & axles to the correct dimension will the brakes, etc. work? If a shorten housing will work, who can I get to do the differential shortening job, here in the midwest, or is this a project that can be done in my well equiped garage.

It's not just the length. The F-body rear does not have the upper control arm mounts cast into the center section.

The f-body rear is basically the same inside also. The only real difference is the axles are 28 spline vs 26.

Putting the effort, time, and money into an F body rearend to work in your Elky is not worth it...the end result will still be a weak rearend with 28 spline axles. Look at other options, if not a 8.5" 12 bolt or 9" ...possibly using your 7.5 housing but installing a 7.5" 28 spline posi unit and using Grand National axles, this will at least eliminate having to shorten the housing and welding brackets on that will work...you'll at least have stronger axles and nothing more. A 7.5" is a weak rear, replace a weak part with something stronger and the next weak point becomes the problem, but unless you really need a stronger rear for performance reasons, a 7.5 will last...just don't abuse it! Disc brakes can be fitted to any of them.

Putting the effort, time, and money into an F body rearend to work in your Elky is not worth it...the end result will still be a weak rearend with 28 spline axles. Look at other options, if not a 8.5" 12 bolt or 9" ...possibly using your 7.5 housing but installing a 7.5" 28 spline posi unit and using Grand National axles, this will at least eliminate having to shorten the housing and welding brackets on that will work...you'll at least have stronger axles and nothing more. A 7.5" is a weak rear, replace a weak part with something stronger and the next weak point becomes the problem, but unless you really need a stronger rear for performance reasons, a 7.5 will last...just don't abuse it! Disc brakes can be fitted to any of them.

This is exactly what I did, 28 spline axles from a Grand National with factory 3.73 gears and factory posi, along with a Trick Flow rear end cover for added strength. Low cost upgrade for much better perfomance!

Something I've wondered... Why will a g-body 7.5 blow so easily behind a real engine, but the f-body rears hold up in LS1 cars? Or maybe they don't and I just haven't read about it...

Something I've wondered... Why will a g-body 7.5 blow so easily behind a real engine, but the f-body rears hold up in LS1 cars? Or maybe they don't and I just haven't read about it...

LS1 F body cars are shredding trannies and rear ends, especially the ones that are being thrashed at the track. Sticky tires naturally add to the problem.

My Firebird has a 3.42 posi unit in it. So if I understand correctly, I can take this center unit out of the Firebird, and install it into my Elky along with some Grand National 28 spline axles and I should have a stronger differential for my new ride.

I have a 2000 SS camaro with the 10 bolt torsen dif, I want to put 410s in it, and there have been many debates on the ls1tech forums, everyone says the 10 bolts don't last, which i bet is true if you beat the hell out of the car, but I have also seen people running 500 hp through 410s in them. So I guess its in the driver and the maintence.
I'm building this 1970 el camino and I was considering putting a 6.0 liter with the t56 6 speed behind it then a torsen rear, but thinking about I'm prolly better of just putting a spool in the old rear end. Much less work, and not worth the efforts since I'm just selling the car when I'm done. I might not even follow through with the 6.0 liter cause I feel like I might lose profit margin if I go through will all the work even though it would be a bitchin ride.
Anyways, I would prolly agree to avoid trying to swap the whole rear end. Most f body owners go out and buy a 12 bolt moser.