Hey guys I was driving home today and i noticed that when im going around 20-25 and I coast I can hear this clanking sound coming from under the truck its not like a fast paced sound but I can hear it over the motor when im coasting, I also noticed my tires have sounded a lot louder in the past day or two idk if that has anything to do with it but the truck goes into gear fine and it shifts through all the gears fine (auto tranny rebuilt 80k miles ago) I checked the driveshafts and they have no play in them, I put it in 4low though and when I release the brake to take off the truck accelerates and then it slows down and then it like releases and does it again, Please help! This is my daily driver too and its my first diesel.....

 

u joints on the front end maybe? had the same issue with my half ton last year. unit bearings are easier to pull off the knuckle than the old shift on the fly hubs. shouldnt be too hard if thats what it is

 

pull the plug on the diffs and see if its coming unglued. if its parts are disintegrating the oil will have particles and could look like silver paint. only reason i said diff is the clanking and the hanging up. could be a cracked brake drum or rotor too

 

front ujoints at the end of each side of front axle