Have 69 Dart 4 speed ! Just bought it ! Has 2" narrowed rearend. Had to make up new driveshaft. [had b body 4 speed] . Professonly made, balanced, I had it made up maybe a little short...2" out of tailshft. Any way I got bad vibrations 45 mph and up. Ideas ???????

 

Chris -

Welome aboard.

A perfectly balanced drive shaft that's 2" too short can give subtle or not so subtle vibration, usually when decelerating. Don't ask me how I know ...

The fact that you're getting it at a specific speed or rpm still suggests that the drive shaft may not be balanced as well as you think or one or more of your wheels/tires hasn't been balanced. The U-joints may also have to be looked at for alignment.

Archer

 

I don't have the answer for you but, welcome!

 

welcome..
i my self never had a problem with the u joints not being aligned
i have seen professionally balanced driveshafts not be balanced correctly.
also tires being out off balance. if you have adjustable axles and they don't have the play needed (to tight) that can cause a vibration also.

 

also dont have an answer, but welcome. and thanks for teaching a drive shaft can be out of balance. learn somthing new every day

 

Thanks ! I'll double check it ! Chris

 

You can check driveshaft balance yourself, now I'm doing this from memory and at 56 that can be iffy. First get yourself a couple of hose clamps that will go around your driveshaft. Take one and put it on the shaft, TIGHT (mark shaft in quarters). Take the car for a spin, if the vib is worse move the clamp 180 degrees, take car for a spin again if it's worse still move clamp back and add other clamp in the same position, take car for spin and see if it's better. In short move one or two clamps around and see it you have any improvement, if not the problem is elsewere.

BTW, I went thru this with my Cuda after I bought it only to find that there was no nuts on the tranny mount!!