I have an 8.5 lying around. What would I need to do to replace my 7.5 with it? I can't find any info on doing this kind of swap and was wondering if it was possible on our cars... labor is cheap over here in case I need to unweld brackets and weld them on the 8.5...

 

Short answer, no .

Long answer, anything is possible! I'm willing to bet SOMEBODY has done it, but I know this has been discussed before, and I can GUARANTEE you it would require A LOT of custom design and fabrication to make it work. And then, even once you've got it IN the car, the axles are way shorter than the 4th-gen, so you'd need crazy spacers or lug adapters, and/or longer axles (if they're even available? ) so I just think it's way too much work and hassle, when there are perfectly good 12-bolts and 9" diffs out there that WORK with NO p!ssing around to make them fit . Heck, I've heard of guys doing Ford 8.8" swaps ... I think one of those would fit easier than the old 8.5"?!

 

The answer is yes and no...

Yes there are guys who have fabricated one to fit a 4th gen but its expensive.

You will have to cut all the mounts off your stock rear and weld them all onto the 8.5. You will most likely have to shorten the rear also. With that you will need new axles, bearings seals ect... Your tq arm will need to be modified to fit, ABS and brakes are different, ect...

In the end, if you pay someone, you could have bought a 12 bolt and a 9 inch for the money you just spent.

If you can fabricate everything yourself and you dont mind the countless hours of labor you can do it for around $1000 in parts.

But you have to ask at that point, for anouther $800 you can buy a complete rear and have it shipped to you with a warranty in half the time. You screw up your angles with the 8.5 and all your work is out the window anyway. You also have a rear that is not as good or as strong.

So yes it is possible. No its not worth it.