Looking for Challenger Drive Shaft w/7290 Joints

[cwestra]

I am looking for a good used drive shaft around the length of a Challenger (45.60" or 45.85").  Must have the larger (2.625") 7290 yoke on both ends, with standard 7.625" long, 30 tooth, slip yoke.  I will be cutting it down to around 45" so it will work in my Cuda.  Currently I have about 2.5" of slip yoke extending out of the tail shaft with the standard length (43.60") drive shaft.  I believe this is the source of a vibration I have been having with the car.  I can't explain why the correct length shaft is not extending far enough into the tail shaft, but it isn't.

1)  I've been told that shortening a Mopar drive shaft of this type (tapered down at rear) must be done at the rear, due to the internal construction of the shaft (something to do with an internal tube in the front part).  Can anyone confirm this?  That's the main reason why I am searching for a shaft slightly longer than what I'd be cutting it down to.  With a longer B-body shaft I would be cutting the entire taper, or stepped down diameter, from the rear.  If I could shorten from the front it wouldn't matter what length it was, as long as it was at least 45".

2)  My current shaft has 7260 joint up front and 7290 in rear.  Did Chrysler ever produce a shaft with this configuration, or was my shaft likely modified at some point (for some unknown reason)? 

3)  I noticed that my current 7260 slip yoke has the splines starting about 1.5" in from the front of the yoke.  Is this the same on the larger 7290 yoke, as well?  What was the reason for not extending them all the way to the front for better engagement?

[Cuda54]

I had a full size car shaft cut down by a shop to fit my 72 cuda. After I dropped the small joint shaft out of my car. I had a new big yoke on the dif with the big yoke on the front of the shaft. They checked it for balance and made sure it was straight with new heavy duty joints too. Old full size cars are all over and easy to find.

[rebelcuda73]

This sounds like the same issue that I had to deal with my 74 cuda. Mine originally came with a 318 with a 904 auto trans and 489 rear with 276 gears and smaller u joint, but had larger for  the trans . I changed out and installed a 68 440 with a   a833 23 spline trans. But the drive shaft no longer fit. Wound up using a u joint in the rear that had both size u joints in one until I decide to change out rear. Its the center on the rear that needs to be changed to use larger u joint , I think around  80.00 or so. What I learned is that the 904 trans uses a certain drive shaft that is longer in length and uses smaller u joints. The 727 and the a833 trans uses the shorter drive shaft with the  larger u joints. I don't know  what combo you have in the car but if you are using the 904 trans  I have the right drive shaft for your cuda in my garage and I am looking to get rid of it send me a message if you need it. Otherwise I hope the info helps you out!!

[rebelcuda73]

Hey I checked the info I gave you and I made a mistake. My bad!!! I measured both of my driveshafts and the one you need with the larger holes for the u joints is about 43 1/2 from center hole to hole and the holes are about a 1 1/8 . This drive shaft would be the one that fits both the 727 and the a833 trans. I found  mine for about 80.00 at a swap meet. And if you don't want to change out the center of the rear to fit the larger u  joint they make one that is both but the larger is stronger.

[cwestra]

Hey I checked the info I gave you and I made a mistake. My bad!!! I measured both of my driveshafts and the one you need with the larger holes for the u joints is about 43 1/2 from center hole to hole and the holes are about a 1 1/8 . This drive shaft would be the one that fits both the 727 and the a833 trans. I found  mine for about 80.00 at a swap meet. And if you don't want to change out the center of the rear to fit the larger u  joint they make one that is both but the larger is stronger.

Thanks for the feedback.

Actually, I do have what should be the correct length in mine right now (43.60").  But there's a couple of unusual things going on in my set-up for some unknown reason.  First, I have the small 7260 joint up front (slip yoke) and the large 7290 in the back, not a likely configuration from the factory.  And second, even with the correct length (43.60") I still have about 2.5" of slip yoke sticking out of the back of the trans (A833).  I don't know why it's like this but I've come to the conclusion that what I need to do is just size a shaft that is about 1" to 1.5" longer than 43.60" to try and take care of a vibration I've been fighting, which is why I'm looking for a longer one to cut down (assuming I'm not going to be lucky enough to find one that length).  And I have been told that you can't cut Mopar shafts from the front due to their "inner tube" construction.  They must be cut from the back, where the stepped down diameter is.  So I'm looking for a shaft that is not so long when I cut it short I've removed all of the stepped down section.