Got a new to me 05 Mack Granite with a 460 hp E7, 18 spd Eaton, and 44000lb rear axles with camelback suspension. Also has the large floaters on the front. Got a vibration that starts at about 35 mph and gets a little better around 60. Any idea where to start? Thanks for your time.
tire
If it's not a tire then check u-joints and pinion shaft bearings.
Where are you feeling the vibration? Steering wheel? Floor? Clutch and shift lever?
:iagree
Thanks for the help. Feeling the vibration in the floor and seat mostly. Not in the steering wheel or shifter.
It's probably going to be in the rears then. Are you hearing any noises like whining or squeaking? What type of wheels are you running? Full disc Budd type or clamped on rim? The clamped on type need to be tightened evenly or they will create a wobble and vibration. Could also be a bad u-joint or wheel bearing. Might help to take it out on a highway and have a spotter drive behind and along both sides and see if he sees or hears anything.
A common source of vibration that goes overlooked is loose slip joints in the drive shaft. It lets the shaft get crooked as g forces rise from the rotation. Also check you steer tires for out of round, you can balance a oval but the cam action will shake the truck at speed.
Thanks to all who replied. The new tires (cheap) were out of round. Previous owner had the new tires on it (Lamarch??). But that is what it was.