Shake when driving

Could be rear bushings, could be a u- joint, carrier bearing, broken spring.

 

Could also be a bent rim or rear shock problem.

Could also be an engine issue, but more likely a drive line issue.

 

yes.

 

Does the vibration start in the steering wheel or the floor?

 

Cupping or step wear on drives is usually from bad rear shocks. Vibration? New shocks, check the ride height, Volvo has a frame mounted adjuster, two different settings, depending on width of frame rails. As mentioned the rims, and rear spring bushings. Check the whole driveline for play. Starting at transmission tail shaft and yoke, carrier, all U joints, drive shaft and rears yokes. If it’s good leave it alone. Throwing parts at it can be expensive and aggravating. Check the whole front end, Bad engine and transmission mounts are sometimes the culprit when all else is good. If the Trucks over 7 years old. It’s possible.

 

Vibrations are always difficult to pinpoint because there can be so many causes. This^^^ helps. Generally, a shake in the steering wheel indicates something in front, while a shake in the seat, or floor, indicates something in back. A bad U joint usually vibrates under power. Things like bearings or mounts don't "go away" and I suspect a balancing problem. Brake drums, driveshaft, and of course wheels and tires have weights and, I'd start there. The reason it's prevalent at 65, is that's the speed it probably ran for years. A worn engine harmonic balancer I heard, causes weird vibrations too.