Going from a 71/4 to an 8 3/4 rear in a 1970 Challenger with 904 automatic

[DY31970]

Can the driveshaft with the 71/4 be us when switching to an 8 3/4? Or will a different length length driveshaft ben needed?

 

[Chryco Psycho]

I recall it is about 3/4 " shorter with the 8 3/4
You might just have enough travel in the slip yolk but you do not want it going solid through the range of travel

 

[pschlosser]

Agreed. The parts book shows the 8.75 drive shaft is about 2.00 inches shorter on the Challenger 1970-71.

P 3578 778, 318 Eng, A904 Auto, 7.25 Axle, 52.03 x 3.25 inches, 2.125-inch Yoke
P 2883 779, 318 Eng, A904/727 Auto, 8.75 Axle, 49.95 x 3.25 inches, 2.625-inch Yoke

 

[413]

Shorten it or get a another, don’t try to force it in there. It won’t be a good happening.

 

[DY31970]

Thanks guys for the information. So the driveshaft is 2.08" shorter for the 8 3/4, and the yolk is .50" wider for the 8 3/4.

 

[moparleo]

Here is a factory spec chart.