I have a 97 Chevy Silverado extended cab 2 door pick up, I've been trying to figure out why I have a vibration over 45 miles an hour when coasting and I give it a little bit of gas it vibrates in the rear, slows the truck down just a little bit if I keep giving it gas it goes away if I let off the gas it goes away but in perfect conditions I can hold it there for a long time and it's definitely in the rear of the Truck
I have replaced all the bearings in the differential axle bearings new U-joints the driveshaft is perfectly balanced I checked it with a cup of water hanging from the differential I did not replace the differential itself it's limited slip and I did not replace the ring gear and pinion gear does anybody have any idea I sure would appreciate some help I'm about at my wit's end with this thank you
Mountain Mike

 

Last time tires were balanced? Could try rotating tires and see if problem moves to the front.
BTW welcome! Lots of smarter folks here than me that can help you!

 

Welcome from Miami.

 

welcome from maryland