vibration and droning

[rattlesnake]

The 70 cuda runs wonderful but has had a droning noise accompanied by a vibration. I cannot tell where it is coming from for sure, sometimes I would swear it is coming from the rear but other times I think it is coming from the front. I don't really know how to explain the noise other than to say it is intermittent, it sounds like something caused by maybe a gear with one side of the gear worn or rusty. It disappears completely when I let off the gas but is always there while cruising or under acceleration. I replaced the rear U-Joint thinking that would fix it but it did not. The front U-Joint feels solid. I also thought maybe the driveshaft is out of balance. What a puzzle. Any thoughts?

Rattlesnake

[1 Wild R/T]

http://www.cuda-challenger.com/cc/index.php?topic=93146.0

[jhaag]

Manual or auto? If noise goes way under deceleration it is most likely the rear gear. Could also be in the trans if a manual.

[734406pk]

Do you feel this vibration/ noise in the floor pan? Or maybe the shifter if a manual? Take the rear seat out and go for a drive or have someone else drive and listen to the rear axle etc. could be pinion bearings?

[rattlesnake]

The cat is an automatic. I am wondering if it is the tires because it sounds and feels differently depending on what road I am on. I am running the triple nickel Nittos. I does sound like it is coming from the rear.

[burdar]

I know in the 80's the factory bolted a big weight on the back of the transmissions.  I think it was supposed to cut down on some vibrations.  The bolt holes are already in the tail shafts for the weights.  Would adding weight at the tail shaft do anything in this case? 


EDIT:  I just googled those tail shaft counter weights.  A few people have reported that those weights fixed their driveline vibrations.  One guy bought a new balanced driveshaft, rebalanced his tires and checked his pinion angle.  The vibration was still there.  The weight on the back of the trans fixed it. 

[734406pk]

I know in the 80's the factory bolted a big weight on the back of the transmissions.  I think it was supposed to cut down on some vibrations.  The bolt holes are already in the tail shafts for the weights.  Would adding weight at the tail shaft do anything in this case? 


EDIT:  I just googled those tail shaft counter weights.  A few people have reported that those weights fixed their driveline vibrations.  One guy bought a new balanced driveshaft, rebalanced his tires and checked his pinion angle.  The vibration was still there.  The weight on the back of the trans fixed it. 

This is possible. I've seen that weight before, some have it and some don't. I would try to drain some lube from the diff and check for metal and adjust your tire pressures to see if it changes the noise. At least you know it's coming from the rear axle. Does this car have an 8-3/4 rear?