I have a '72 Duster doing back in with a small block and A-904. I am taking out the 7 1/4" and replacing it with either a 8 1/4" or 8 3/4" rearend. Which combination will I have the least trouble finding a driveshaft that will bolt right in, no modifications?


bwhitejr

_________________
'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

By that criterion, existence of perfect-fit driveshafts, if this were the year 1989, I'd probably say the 8¾" would be the one to pick, because that was a factory-available combo so the correct-length driveline exists and all you have to do is find one. But, this being the year 2006, my answer changes to:

It doesn't really matter much. Make the rear axle selection based on another criterion. There's not enough difference in driveline length between 8¼" and 8¾" rear axles to exclude drivelines from one configuration being used in the other, and you're likely to have a tough time finding any factory driveline of the correct length without measuring, given that the junkyards are no longer full of A-bodies. Best thing to do is install the rear axle you will, measure the length you need, then go down to the wrecking yard and start measuring drivelines. If you're lucky enough to find a yard that has racks full of pre-pulled drivelines, go there!

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Not to hijack the thread, but what exactly is the correct procedure to measure for a new driveshaft? I've been thinking about a tranny swap sometime in the future, and I doubt the new one will be the same length.

From centreline of rear U-joint cap to centreline of front U-joint cap, allowing enough in/out slip of the slipyoke (take heed of whether you're measuring with the car's weight on the wheels or off...)

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

8.25 and 8.75 will use the same driveshaft. It will be 1.75" shorter than the one for the 7.25.

_________________
Official Cookie and Mater Tormentor.