Vibration 2004 2500HD

[Hindsy]

I have a 2004 2500HD with around 114k on it. Truck doesn't run the highway very often, but recently on a highway run I noticed a pretty heavy vibration as I accelerated above 65mph. At first I thought it to be an exhaust leak, but as I slowed below 65 it decreased. If I let off the pedal it also quiets down, but increases as I press back on the pedal. is this in the drive train? I'm assuming possibly the U-joint or out of balance? I don't have any issues noticeably when at lower speeds. Thats issue one...

 

I also have been having issues with the 4 wheel drive. recently had to use it and it did not want to shift out of 4 high. During a short trip at camp it said I needed the 4 wheel drive serviced. What type of service should be performed at this point?  While I was hunting it was parked for a few days and was fine once I started it and went into 2 wheel drive. 

 

 

[riverbanks]

Can you try to isolate the vibration for the forum?tough online,where is the feel from you? front,mid,rear?and your transfer case actuator is getting slow to respond 

[Hillwood]

The frequency of the vibration is what helps to isolate it.
Is it more of a wobble or a buzz?

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[Hindsy]

2 hours ago, riverbanks said:

Can you try to isolate the vibration for the forum?tough online,where is the feel from you? front,mid,rear?and your transfer case actuator is getting slow to respond 

 

1 hour ago, Hillwood said:

The frequency of the vibration is what helps to isolate it.
Is it more of a wobble or a buzz?

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Feel is more toward the rear. frequency is more of a heavy hum. 

[Hillwood]

Take the driveshaft off and check the U joints.. they should be smooth and no binding.

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