Switching from 8.2 to 8.5--driveshaft length identical?

Hi guys, when making the upgrade from original 8.2 BOP to an 8.5 Corporate diffy in a GS (1969), will the driveshaft need to be modified? Or can you just bolt it right on without needing to lengthen or shorten it?
Thanks.

 

The drive shaft will need to be shortened 3/4”. That’s it. They both use the same 3R u-joint.

 

I just went through this last weekend. As Brian says, you will need to shorten the driveshaft 3/4".
Greg

 

Thanks, Brian.

 

Thanks, Greg. I knew there would be people here with the answer.

 

JUST REMEMBER... To be absolutely safe. You should install the rear and measure BEFORE cutting the drive shaft or having one built.
AS WE ALL know- Nothing in the world of MUSCLE cars that are over 50 years old is ever just PLAIN AND SIMPLE.
Jim

 

I'm glad I've been following this thread pretty close as I have an 8.5 10 bolt I purchased from Everyday Performance to install after I finish with my 455 build. I already know I'll need a new driveshaft anyway but didn't know about the slight difference between the 8.2 and 8.5 rears. So glad for all the important info on this site!

 

I just switched from a 8.5 back to a 8.2 and didn't change the drive shaft.

 

Presumably you had enough adjustment in your slip yoke to still have sufficient spline engagement ?

 

2.5,
What car did you do that on?

 

It is the 70 stg1 4 speed.
I don't have the car with me to be able to check it.

 

Didn’t that car have a Pontiac 8.2” in it? If so,the drive shaft is the same for the two different rearends.

 

You know, I hadn't thought of that. I didn't do the install but it was done by a shop that is very good at that kind of work and are Buick guys as well as race guys ,so I didn't give it a second thought.