7 1/4 to 8 3/4 Driveshaft question.

[Arizona A-Body]

Im getting ready to change my 7 1/4 out for an 8 3/4 rear in my 69 Barracuda. My question is what do I need to expect to do to my driveshaft. I presume that there is difference in length.

Thanks

 

[64physhy]

The driveshaft will have to be 1 1/2" shorter, and depending on which carrier and yoke, you'll probably have to change it over to use larger U-joints. I think with a 741 with a small yoke, it would be the same (driveshaft would still need shortened). If you can find a driveshaft out of an A body that was equipped with an 8 3/4, you might be able to just get the shaft and save some trouble.

 

[pettybludart]

I have a 66 Dart,6 cyl. auto(had a 7 1/4)I also had a 73 Dart Swinger 318 auto,7 1/4 ?? I put a 8 3/4 with .489 in and used the swinger d.shaft with a larger u-joint.I bolted it in after u-joint swap,it seems to be working no problem(length wise)Hope this helps!

 

[Arizona A-Body]

Thanks for the information guys. Next step, the install!

 

[340 swinger]

The driveshaft will have to be 1 1/2" shorter, and depending on which carrier and yoke, you'll probably have to change it over to use larger U-joints. I think with a 741 with a small yoke, it would be the same (driveshaft would still need shortened). If you can find a driveshaft out of an A body that was equipped with an 8 3/4, you might be able to just get the shaft and save some trouble.

If you do find a proper 8 3/4 drive shaft kicking around take the time and have it balanced. I did the same swap and thought I would save the expense of cutting down the drive shaft and just slid in the proper lenght shaft that I got from a friend. Big mistake. I knew the car had a vibration and ignored it. One evening I decided to try the car on a g-tech and at about 90 mph the vibration got real bad and the cap came off the front u joint. Most of my newly built 727 was laying in pieces on the road.
Just my .02 cents.