Switching from a 7.5" to 8.5" rear end???

[Yedi]

I am going to be swapping my old 7.5 non posi rear end w/ a 8.5" posi I just bought. I have UMI control arms, and a 200r4 transmission. From what I've heard, all I need to do is cut my driveshaft 1" ??? is this right? I have both complete brake setups, your help would be great.

 

[Roc87]

You will more than likely have to shorten the driveshaft. I went from the open 7.5" rear in my elky to an '86 GN 8.5" posi and I had already done the driveshaft for using a 700, and didn't have to shorten it anymore, but I probably should....It's that close. Had I not had the driveshaft done a few weeks before (before I found a decent deal on the 8.5) I would have had it done. My suggestion would be to do the swap and see how much the driveshaft had to be shortened if any. Other than the driveshaft, everything else including brakes are just the same. HTH

 

[fc227]

When I went from a 7.5" to an 8.5" in the Olds. I had to get a drive shaft that was shorter (about 1"). I was running a Th350 tranny, I used a drive shaft out of a GN (Both rear end & Drive shaft I got from Jack Cotton) and it worked out good. The original drive shaft was too long.

I am not 100% sure but I believe the Th350 and 200R4 are the same length.

 

[Bweavy]

8.5 Drive shafts

We have them in stock for $75.00 plus shipping.

 

[Yedi]

thanks for the help guys. as far as I know the th-350 and 200r4 are the same length, when I did the swap, I did not change my driveshaft and it worked fine. Thanks for the offer Brian, I will kep it in mind.