Drive shaft length

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RedFish

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Woulld a 7.25 rear and a 8.25 rear use the same drive shaft ?
The donor car is a 75 Valiant so its longer wheel base would require a longer shaft than the 67 Barracuda too, right ?
 
Everything I have found says that the 7 1/4 drive shaft needs to be shortened 1 1/2" to fit properly. I'm getting ready to do the swap in my 73. Ross is running a stock 7 1/4 drive shaft in his sisters scamp with a 8 1/4. It works but you can feel it.
 
360scamp said:
Ross is running a stock 7 1/4 drive shaft in his sisters scamp with a 8 1/4. It works but you can feel it.
Click to expand...

This cannot be good.

With a properly fit drive shaft, you only have an inch of play between the yoke and the tranny and if you try and use one that is too long you can destroy berrings in the tranny and the rear end. If you run one that is too short then you run the risk of destroying the splines and bushings on the trannies tail shaft or having it come apart and driving the drive shaft into the pavement which will say the least cause a lot more problems.

To correctly check your drive shafts fit. Have the car sitting at ride height, slide the yoke into the tranny all the way then you can pull it out 1" to fit the rear end, no more and no less than 1" if you need more than that or it doesn't come out an 1" then have a drive shaft made to fit.
 
Thats why I wish he wouldn't have said Ross is running, because I'm not the one doing it and I have warned the person doing it that it is not right but said person isn't listening to me.
Anyway I would highly recommend against it.
 
I'm gonna need new U bolts for the 8&1/4 rear too. Anyone know where the best buy on those is ?
 
RedFish, 7 1/4 in. rear centerline of axle to centerline of rear u-joint is
10.09 inches. 8 1/4 is 11.69 for same measurement. Hence, shorten
driveshaft 1.6 inches. Correct me if I'm wrong, but aren't both a 67 and
a 75 considered late a-bodies with the same wheelbase? If it was a 66
it would be an early a-body with a 106 wheelbase.
 
Orv Grote said:
RedFish, 7 1/4 in. rear centerline of axle to centerline of rear u-joint is
10.09 inches. 8 1/4 is 11.69 for same measurement. Hence, shorten
driveshaft 1.6 inches. Correct me if I'm wrong, but aren't both a 67 and
a 75 considered late a-bodies with the same wheelbase? If it was a 66
it would be an early a-body with a 106 wheelbase.
Click to expand...

Thanks for the drive shaft info. The wheel base went from 108 to 111 on just some models. I know 4 door Valiant changed, dunno about the 4 door Darts. anyway... I can get a shaft shortened 1.6 easier than lengthened.
I googled the U bolts and found 7 inch and 9 inch lengths. Dont know which I need.
 
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