Truck cabin vibration at 30mph, stops after

Yeah sounds like tire or drive line vibration

 

Have your U-Joints checked.

 

U-joints or maybe the drives haft is out of phase if you had to remover the drive shaft for any recent work.

 

Ok, alignments never cause or fix vibrations. Never have an alignment done to try to repair a vibration, you are just wasting your money. Volvo likes to use maintenance free, or grease-less u-joints and slip joints. These will dry up after a while and start to seize. The only way to check is to disassemble and try to move by hand.

 

i would lean toward U-joint too, or wheel balance, are you running wheel balancer ? or did you had the tyre balanced when mounted on rim ? if not i would check on that, or maybe snow accumulation inside the rims, seen that a few times, rims is packed full of snow and ice, and it makes the wheels go off-balance ......

 

I have to agree with 4vmach1

 

A drive line problem will usually change with acceleration.

 

Bad injectors.

:smt064

 

i would tend to agree for bad injectors....