Vibration no one can find

i had a vibration like that last year it lasted for 7 months until the front rear chewed off 3 rig teeth ended up the back pinon bearing went bad

 

Try this as a test Pull Drive Shaft between the rear ends. Then see if the Vibration goes away. If so you might have a mismatched set of rear end Ratios. Asked a old foreman of mine if it can happen it does. They just had a Brand New T660 show up with a Front diff at 3.33 rear was 3.79 man that driver was SCREAMING. From what your describing sounds like one is a 3.73 and one could be a 3.75 close but NO CIGAR. Drop a Matched set of Remans in with the same ratio say 3.73 and I can almost bet you it will fix the issue.

 

I don't think that's possible. Two different ratios, one would lock up and shear pinion teeth off. No vibration just a loud snap.

 

injector? maybe one going bad or do you have good smooth power thru all gears?

 

I tend to agree with this statement. This is a stumper and we will all lose sleep until you get it resolvedFurther more, I will continue scratching my head as I am sure the rest are pondering this with you. Baffling.....

 

That would not necessarily preclude it being harmonics caused by engine vibration. Once the vehicle gets the vibration the wave has to cancel itself out.

But hey your truck. Out of curiosity did you check all your motor mounts and frame connections? I still find it more likely than mismatched gearing left undiscovered for a few hundred thousand miles.

 

Wonder if the driver's side sags causing a weight and balance problem? No time for political correctness here we have a problem to solve.

As a side note some people deal with vibration problems better than others. I worked at a auto tire dealership and we did. It is a team effort which is what most places don't do.

 

Mine's the same way under load. No idea what's going on there. I asked Kenworth about it and they had no idea either.

 

your front rear will run hotter than the back rear more gears to turn.