VOLVO VNL 670 VIBRATION HELP

I have seen bad trailer tires cause exactly what you are describing... Check to see if your trailer tires are out of round (egg shaped)... It doesnt take much.

 

Update: I replaced the leveling valve, and rod, and my vibration is all but gone.
The rod had at least an inch of play, both bushings were shot. The valve may have been OK, but I had a new one so I replaced it.

 

How much did it cost you to do all that? I have a similar issue where I get vibration on heavy loads around 50-55 mph in 11th gear. If I drop to 10 I won’t feel vibration but runs or higher rpm. I have dropped both differentials dropped, changed washers seals adjusted bearings but still it’s not gone. Threw on new set of tires, still no luck. Only thing left is what you have mentioned to do.

 

When your transmission was acting up did your engine feel like it was chugging, and were you getting poor fuel mileage? I have a 2013 vnl 780, bobtail I get a kind of jerking sensation feels like unbalanced steers between 55 and 62 mph. When I'm loaded (usually heavy 44k-48k), it happens all the time, except when let off accelerator. Steers been balanced twice now, and hasn't helped either time. Mechanic checked driveline said all was good. I had thought it was carrier bearing, but suppose not. But my engine chugs when it does it too. Watching the tach it's got a tick, maybe of 25 rpm. Doesn't feel like someone pushing in and letting off a clutch and the engine doesn't Rev like trans is slipping.

 

Drive line angles out of specs. Check ride height, rear sprigs bushings and pads.

 

Thanks, where do I find the info for what the ride height should be at? I've measured when loaded, and it's been 40 inches on both sides from ground to 5th wheel slide rail.

 

Ride height is specific to the vehicle. And check drive line angles because worn spring bushings, weak springs can change differential angles and cause vibration