I just had rear end put in from a 80 trans am. It looks a little wider. So anyway I get a vibration in 3rd and 4th gear and make a noice when I let off the gas. If I engage the clutch the hum lessens. So I didn't know if this might be the drive shaft or a bearing in the rear end. Any thoughts?

 

That part right there concerns me and it should concern you as well!

 

check the ujoints on the driveshaft.

 

All 1970-81 Camaro and Firebird rear axles are the same width. Not sure why it would look wider. As for the noise, it could easily be the rear axle, if you didn't have the noise before. I would head back to whoever sold you the rearend and have them check it.

 

Check the oil level. Was it changed?

 

Thanks for info guys. I'll have the driveshaft checked & U joint checked. I think it might be the u joint. I will for sure double check the oil level too.

 

The noise may be due to wear between the ring and pinion gear, backlash increases with age/wear and will result in noise on deceleration. The vibration is more likely the u-joints/driveshaft like stated here already.

 

Found it. As soon as the car went on the lift I saw it. It was a U joint and the bolt that connects the u joint to the youlk was loose. You could rattle the drive shaft with you hands. not good. So I went back to the place where they installed the rear and had them pay for the service. But now the car runs like new. Also made some carb adjustments this weekend and the car runs like the wind. Can't wait for the spring/summer to get some more work done on it.