driveshaft lenghts

[miller]

I am keeping the 8 1/4 in my car until next fall (when the college has time to go through my 8 3/4 rear end). Will the drive shaft need to be a different length to go from the 989 to the 727 transmission, or does the lengths only differ with the rear ends?

[flyinlow]

The 727 is differrent length and a differrent slip yoke.  Most 440 used bigger u joint 7290. Mancinni sells driveshafts made to order if you can,t find one locally.

[miller]

I currently have 3 driveshafts (one from a 67 charger 383 car, one from my 318 charger, and one from the 440 new yorker), which one of these would be the best bet to cut? Also when i put the rear end in would i have to modify the driveshaft a second time?

[flyinlow]

I would think the 67 383 would be pretty close.

Yes I think the yolk to axle length is differrent for  8 1/4 and 8 3/4 However , I started with a 73, 318/904/ 8 1/4.  I swapped the rear axle  to a 8 3/4  first. I drove the car with the 318/904 / original driveshaft for 3 months .  Their is a little wiggle room on the slip yolk/transmission depth of engagement. Try what you have on hand first.

There are two sizes of yokes for the 8 3/4. 7260 and 7290 which is the one for  big blocks. And to make  things interesting there are fine and course spline pinions.

If you have a 7260 yolk on the 8 1/4 axle (probably do) they make an adaptor u joint to mate your 7290 driveshaft to a 7260 axle.

The 8 1/4 was used behind 400 2bbl. smog motors.  A healthy 440 will break it eventually. If avoid slicks and dead hook launches it will live for a while.