Need Help With Driveshaft Issue

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68droptop

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Okay guys, I need some help. I'm doing the last few things to get my Dart on the road after my big brake, mini-tub, spring relocation, tires & wheels project. I went to put the driveshaft in today and found a problem I did not anticipate. I have two driveshafts, and neither one will fit.

I bought this car last fall and for now I'm leaving the 318/904 in it to drive this summer. This car had 7 1/4 rear, but I just installed an 8 3/4 rear from my '69 donor car. It's now has a 904 trans with a 8 3/4 rear end. I have two driveshafts, and neither one fits.

One shaft is from the 904/7.25 car and it's too long and the u-joint is too small for the rear end yoke. The other shaft is from my old '69 Dart 440/727/8.75 donor car. It is too short. I didn't check, but I think the shaft yoke is too big the the 904?

What do I need to do? Am I missing something obvious?

Thanks for your help!
 
When you mix match engines, tranny's and rear combos like this you got one choice and that is a custom drive shaft. The BB and 727 is a longer assembly therefore needing the shorter shaft and the 7 1/4 and 8 3/4 aren't comparible.

terry
 
This has me thinking..
Ill have to make a post. but what about an aluminum drive shaft out of a new truck?
one of those huge light super strong ones? would it work?
 
Couldnt you have the shaft shortened? Also, I believe they make u joints that fits two different sized yokes.
 
It only costs about $50 to have a drive shaft shortened and balanced. I have done it twice now; first when I replaced the 3 spd manual with a long tail shaft A833OD and second when I swapped the 7.25 for a 8.25.

You can get a conversion u-joint at NAPA that will fit the smaller yoke on the drive shaft and larger one on the 8.75 or get the small u-joint yoke for the 8.75 or when you have the shaft shortened have them put the bigger yoke on the shaft.
 
If you wanted a factory driveshaft you would need to find one out of a 4speed - 8 3/4 car, it would be the right length. You are correct than the 727 yoke is different than the 904 yoke. Also if you found a 4 speed driveline you would have to put your 904 yoke on it because the 4 speeds have the same yoke as the 727. A 3 speed manual - 8 3/4 driveline would bolt right in because the 3 speed manual yoke is the same as the 904. Now that I made your head hurt from all this, it would be easier like the other guys mentioned to get the long one shortend.


Chuck
 
I've decided to shorten the longer shaft and use the conversion joint at the 8 3/4.

Thanks for all the help. I appreciate it.
 
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