7 1/4 to 8 3/4 Newb Questions

RustyRatRod said
Really? All of them I've ever seen needed the drive shortened on the order of "around" 1.5". I guess it's possible I'm remembering something different.

19DART66 said
RRR is right, you are going to have to shorten the drive shaft.
7 1/4 10.09 inches from center of ring gear to end of yoke
8 3/4 12.35 inches, that is a 2.26 inches difference in length.
So measure the drive shaft that is in the car now and either take 2 to 2 1/4 inches off, with 3/4 to an inch of slip yoke travel or find one that is that much shorter.
Other Mopar axles for reference,
9 3/4 Dana 13.47 inches
8 1/4 and 9 1/4 are both 11.69 inches
These measurements are for Mopar factory yokes if using aftermarket yokes measurements may very.

My 68 Barracuda with a factory 7 1/4 rear end and a 904 automatic transmission.

Installed a 8 3/4 rear end from a 1971 Demon 340.

741 case , small yoke.

Installed with no modifications to the original driveshaft.

When I installed a 727 small block transmission from a 70 340 Duster, I had to use the driveshaft from that car.

No issues, worked fine.

I still have both driveshafts so I will see if I can dig them out for comparison.