8 1/4 Driveshaft Q's

[MOPARJ]

I have my 8 1/4 now in my 73 Duster. I have a 8 1/4 driveshaft thats the right length, but its bent and I do not want to use it, since it is quite a bit larger in diameter for some reason. Every small block car I have had has always had about the same general diameter for the ds.

I am going to take them both to the driveline shop (7 1/4 unit and 8 1/4) on Monday and have them compare the two and shorten the 7 1/4 down to size and rebalance.

My question involves the u-joints. My 7 1/4 shaft has good u's on it currently and I would like to reuse them. Should they match up with the yoke on the 8 1/4 rear, or is there different sizes?

 

[dgc333]

They should be the same size. I put an a-body 8.25 in my 68 Barracuda to replace the 7.25 and the yoke on the 8.25 was the same 7260 size u-joint as the 7.25. I shorted the 7.25 drive shaft.

NOTE: the drive shaft shop I use won't balance a drive shaft with used u-joints. They insist on new ones but they were the cheapest place around, $30 for a pair of Spicer u-joints.

 

[dodge freak]

My drive shaft was bent and the shop straighten it. They told me most are bent

 

[66dartgt]

Might I suggest measuring the distance from the tip of the trans output shaft to the face of the axle companion flange with the car on the ground ?

Take that dimension with you when you visit the driveshaft shop and tell them to shorten the unbent shaft to the correct length based on your measurement. Sometimes you might find that the correct length driveshaft is longer or shorter than one you know came from the correct vehicle application. Most driveshaft outfits will ask for the measurement for thoroughness. No need to do it twice !

Good luck with it !