7.5 to 8.5 Swap

[ve3oky]

I just read in one of the forum threads:

"8.5 10 bolt rear axle assembly. Found in 84+ H/O or 442, and turbo cars only. May also be found in other models as a swap over the years. Comes in 3.42 on Regal models and 3.73 on Cutlass models. Posi is optional, not standard. Requires a 1 inch shorter driveshaft."

This is the first I've heard or read that the drive shaft will need to be changed, can anyone confirm?? or am I reading it wrong?? thanks.

 

[FE3X CLONE]

Driveshaft needs to be changed. The 8.5" driveshaft is 1" shorter than the 7.5" driveshaft.

 

[ve3oky]

well that sucks .... makes my plans hard 🙁

Here is my situation, looking for input/suggestions. In order to get my car "saftied" I need to do brakes and brake lines. I have a lead on a 8.5 rear thats fully built was thinking that would solve my saftey issue. I'm also in progress of building up a BBB 430 with a TH400 that I was planning to stick in later.

I cant see the engine being done in the next year, its a slow project .. but I hate the idea of needing two new drive shafts (one after putting the 8.5 in and one a year later for the engine swap).

Should I just do the brakes in the 7.5 and do everything else later??

 

[dogsht]

You normally just get the driveshaft from the donor car that had the 8.5 in it.

 

[ve3oky]

You normally just get the driveshaft from the donor car that had the 8.5 in it.

Ya I think the drive shaft is long gone/lost ... I will keep my eyes open on the used parts lists, glad I double checked.

 

[85GPLef41]

if you have a line on a 8.5 then definetly jump on it The drive shaft would be alot cheaper getting it done twice then blowing up the 7.5 and starting back to square one... I thought the th400 had to use a 1in shorter driveshaft as well? could be wrong though...

 

[Blake442]

Just have your stock driveshaft cut and rebalanced.

You'll need a 1" cut for the 8.5" rear.
You'll need another 1/2"-3/4" cut for the TH-400.

I had my driveshaft cut and rebalanced locally for about $90.