99 3/4 ton diesel 4x4,241hdwhen in 4wd i have loud clunking under front of truck.iv'e checked in the diff and both axle u-joints and front bearings.all look good, could it be the front drive shaft u-joints making this noise?any body had trouble with this?thanks in advance

cv joint in the front shaft sounds like its shot

Is it worst when you have the steering cut hard vs straight ahead?

either your u joints or the double cardan on the Front DS

be careful if it is your front cv joint.i broke mine this year.as it did took out my fass fp wire harness wrecked the end that mounts the drive shaft to the transfercase & broke the rear trans. fluid line off the trans. which was the hardest part to fix.if the noise does not appear to be from a ujoint it may be an issue with the engage fork or collar inside the axle housing.hopefully it's just a ujoint their not too bad to replace.

The unit on the front driveshaft is called a Double Cardan joint, not a CV joint. A Double Cardan joint consists of two u-joints and a middle ball joint held in place by springs. Its purpose is to cancel out u-joint angle vibrations by allowing the differential pinion angle to be set at a different angle than the TC output u-joint. When the u-joints and ball joint dry out or get contaminated from road salt, ect., then the DC can vibrate and make lots of noise. Turning simply causes driveline binding and will aggravate the situation. You have the CAD front axle so its not a concern "IF" you're not using 4wd but as mentioned, if you're using 4wd then be careful because if the DC is in poor enough condition, under high load conditions it can break which will cause all kinds of damage under there.

BIG thanks to all.it was the front prop shaft.i would have thought it could have been re-built, but nobody had parts.$280.00 , 1yr warrantyMERRY CHRISTMAS everybody

Always keep an ear our for your Central disconect collar popping off too. Vaccum accuated diaphram goes bad and makes for costly repair. Just for future problems...

i had the same noise. i opened the front diff and everything looked good and my father in law was under the truck helping me and noticed the drive shaft(transfer case side) had a lot of slop in it. took it out and replaced the u joints($160)and the noise is gone. my not be your problem but i had the same sound and that fixed my problem