Eight and three-quarter rear end driveshaft issue

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Tad

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Hey guys, got the eight and three quarter-inch put in and got the correct length driveshaft to my 904. I went to hook it up at the third member and realized the joint on the end of the drive shaft is too short side to side. When I put it into the third member there’s about a half inch space on either side. Is there a special joint that goes in this one? Something that goes from an a body drive shaft to a third member out of a B body?
 
Short answer is yes.

There are 3 u joints typically in mopars 7260 (small) 7290 (large) and another I don't recall off the top of my head.

Looks like you need a 7260 to 7290 conversion joints.

BUT measure, measure, measure before you order
 
Forgot to mention... Other options are change the pinion yoke, or the driveshaft yoke
 
Yeah, there is a special conversion joint that you need to use that has a shorter length for your driveshaft and a longer length for the rear end. I’ve used it two or three times, but I don’t remember the number for it. I’m not sure the auto parts stores can help you out either because they don’t seem too knowledgeable about such things. Maybe somebody here can chime in with the correct part number.
 
your local auto parts store can get it also, 346 is the no. they should be able to interchange it.
 
On a side note... How long did you make your drive shaft. center of joint to center of joint?
 
Dana67Dart said:
On a side note... How long did you make your drive shaft. center of joint to center of joint?
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It was already made to fit the 8 3/4 rear end. I measured 57 1/4 from rear center to the front edge of the pleats that bolts to the transmission. It still has the old-style hook up in the front.
 
Tad said:
I measured 57 1/4 from rear center to the front edge of the pleats that bolts to the transmission. It still has the old-style hook up in the front.
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Ok thanks

I forgot to ask what car? year?
 
Tad said:
I measured 57 1/4 from rear center to the front edge of the pleats
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Wow, that seems way long. My 74 Dart Sport was only 48 3/4 inches center to center on the U joints. Did you measure with the rear suspension hanging or did you have jack stands under the rear axle tubes with the weight of the car on it?
 
Bad Sport said:
Wow, that seems way long. My 74 Dart Sport was only 48 3/4 inches center to center on the U joints. Did you measure with the rear suspension hanging or did you have jack stands under the rear axle tubes with the weight of the car on it?
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Suspension was hanging. New rear springs as well. It’s a 65. The original driveshaft that went back from the 904 to the 7 1/4 inch rear end was around 61 inches long.
 
Bad Sport said:
Wow, that seems way long. My 74 Dart Sport was only 48 3/4 inches center to center on the U joints. Did you measure with the rear suspension hanging or did you have jack stands under the rear axle tubes with the weight of the car on it?
Click to expand...
A 74 Dart Sport is essentially a Duster and has a 108 inch wheelbase. A 65 Dart has a 111 inch wheelbase. Of course, that doesn't explain nine full inches difference.
 
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