I have a 2000 4x4 CTD long box,I have noticed a groan or binding type noise on deacel as well as acel,about 12-20 mph,drop it out of gear(auto Trans) and noise is not present.I had one guy tell me possible retainer clip on rear output shaft in transfer case may be broke,took it apart and it was fine.I am thinking possible rear axle,carrier bearings or spider gears,the truck has 188k on it.Just like to know if anyone else has run across this problem.

 

Check the oil in the diff for metal etc. I would also check the pinion for slack and see if that may be the culprit.

If nothing jumps out at you run it awile longer and see if it gets worse and is easier to find.


Good Luck

Jason