Noticed recently that the truck is exhibiting a what seems like slack in the drivetrain at highway speeds. Basically if I'm on the highway and come off the throttle for a moment, then get back on it there is a clunk like the driveline is re-engaging. Not sure what might cause this. Any thoughts?

Within the last year: replaced transmission and rearend if that helps.

Hmm, wonder if I should check those u-bolts...

 

Did you check the u-joints yet?

 

...could be the slip yoke splines are dry..or worn...

 

I would put my money on the u-joints. You can check it by putting the truck in neutral and crawling underneath and rotating the driveshaft back and forth with your hand. At that point you should be able to pin point were the slack is coming from.

 

Don't overlook checking all mounting points such as spring perches, axle to spring u-bolts, transmission and motor mounts.

 

Thanks for the suggestions. Wrecked my knee a couple of days ago and now i'm laid up on the couch not driving and certainly not crawling around under the truck. I'll let you know what I find once I'm mobile again.

 

That doesn't sound good. Take care of yourself!

 

Maybe the noise was coming from your knee.