Take the existing rear ujoint and see if it fits properly in the joint sadle of the pinion gear. IF it fits, then the size is no different. Slip your driveshaft into the transmission and see if it will fit into place. Slide the yoke into the trans as far as it will go. When you lift your driveshaft into place, see how far the drive shaft slides back into place. If you have to slide it back more than 2 inches, your drive shaft is too short. If it doesnt slide back any, or less than 2 inches, its too long. If its too short you will need a new driveshaft, if its too long your existing one will need to be cut down. Dont try refabricating your drive shaft yourself. You have too much at stake. Cutting or fabricating driveshafts require machinery to balance them.
If the drive shaft doesnt fit; IE too long , slip the front yoke into your transmission and measure the distance from center to center, from the u joint in your yoke, to where the ujoint should be in your differential. Take this measurement and your drive shaft, old u joints, yoke etc to a driveshaft shop in your area. Give them the measurement you have. Be sure to push the yoke into the transmission as far as it will go. Do this measurement with the vehicle resting on the axles. If your rear axle is just hanging loose, you could get a false measurement. Do you have the driveshaft that came with the rear end you installed? If so, you
If you have the drive shaft that fit your new rear end, you may want to compare it to your old one as well. If the rear u joint is different for the new rear, then having the driveshaft or at least the rear u joint yoke from the drive shaft that fit your new rear will be needed when they make the new driveshaft, providing the two rears use different u joints.
If it's any consolation, I had just taken a
12 bolt drive shaft and I cut it down to fit
the 10 bolt. The only difference was
the cup size on the 10 bolt rear yoke was smaller
than the cup on the drive shaft.
So I got a U-joint with two different size
cups and that's it.
I would venture to say if your just swapping
rears you shouldn't have any major problems.
Unless you have a Th400 with a bolt in trans yoke
out of a Grumman...like I do, "now there's some problems ".
"There isn't anything that one can't overcome" :thumbup: