Just got my truck a few weeks ago and just now fully testing the 4 wheel drive out since the roads are bad, ive noticed in 4th gear with 4 wheel drive im getting a bad vibration in the floor boards below 1500rpms, and it only does it in 4th with the rpms being lower then 1500 also tonight i noticed at the stop sign i went to turn and heard a clanging noise, any ideas?

 

I'd be looking at some U-Joints first. I had a bad U-Joint in my front drive shaft, closest to the axle, and it caused all sorts of issues. 4X4 didn't like to engage quickly, and made a good clunk when disengaging. It also made funny noises while turning in 4X4.

 

joints

 

check CV joint and all U- joints. Pull the shift motor off the passenger side of the front axle, and check to see if the intermediate shaft bearings are good. the two shafts might not be lining up for the collar to mesh and will cause a clatter. if the bearing is bad there will be alot of metal shavings in the gear oil. note: a bad CV joint can cause lots of trouble. i replaced a friends T CASE cause of a bad CV joint. it got to clankin' real bad and scattered the T CASE.

 

Probably leaning towards your drive shaft u joints. They will make a nice vibration at cruising speeds. Front ones because if it only does it in 4wd, thats the only time there is torque going to the front axle.

 

mine clunks real bad going straight. pulled cover off pass side and pass side axle is kind loose i guess you would call it doesnt really line up for collar to work. i can take my fingers and move axle around. what part is bad and how do i fix it?

 

ive noticed now, not even in 4wd that at the bottom of 4th gear i get a slight vibration noise, cant really tell if its normal or not

 

I'd check U-Joints,take the shafts right out & check, sometimes only one cup-bearing is bad thats enough to cause intermittant vibration,the other posts were valid ideas also. Jeep98,I think ther are bearings either side ofthe collar to support the 2 piece axle,make sure if you take out the outer side to clean out the housing so you don't get debris into the seal. I also lay a "slimjim" or something simalar in the tube bottom to slide the axle into the housing so you don't pick up dirt/rust into seal resulting in a leak.