Help! vibrating rear

[tomgok]

I have a vibration coming from the back of my 76C3, it only happens when sitting at idle backing out of the garage or just sitting at a light. I checked to see if the exhaust was maybe touching somewhere and it is fine. I thought maybe the brakes but I don't feel anything in the pedal. I wouldn't think it could be the rear end because it only happens sitting still. Any ideas ?

 

[KANE]

tomgok!

So, this vibration is only in reverse.. and only at low speed? Does it increase with speed- or as you let off the brakes?

My inclination is some sort of rubber mount, bushing, or something. Could be the cross member to diff mount that sits underneath the u-joint where the diff and driveshaft meet. Could be the u-joint too. Who knows.


What else can you say about it?

 

[Mac]

Motor mount or tranny crossmember loose or failing???

Mac

 

[BigJimZ16]

I have a vibration coming from the back of my 76C3, it only happens when sitting at idle backing out of the garage or just sitting at a light. I checked to see if the exhaust was maybe touching somewhere and it is fine. I thought maybe the brakes but I don't feel anything in the pedal. I wouldn't think it could be the rear end because it only happens sitting still. Any ideas ?

Is this an automatic trans? If so, Motor mount or transmission tailshaft housing support.