I've got a 87 pickup 4x4 5 speed...ive noticed that if i drive in a gear and let off the gas momentarily then step on the gas again, i could hear a quick clank that sounds like something is catching up slack. it sounds to be right underneath the cab about in the middle towards the back, could it be tranny mounts, or maybe u-joints??? how could i pinpoint the problem

 

i also get a clank buts its when im in reverse and turning. You should check the ball joints by jacking the front end and trying to wiggle the tire up and down.

 

Engine off, in gear (say 2nd), hand brake off. Grab onto rear wheel and roll truck forwards and backwards. Observe slop.

 

unhappy, if it has slop what would that mean?

 

It will have slop, brand new right from the factory there is a bit of play in the trans/tcase/axle gears, but watch for WHERE and HOW MUCH and listen for the clank.

Other ideas; shifter hitting the side of the tunnel opening, motor mounts shot, tranny mounts shot, combination of the above, u-joint bad, spare tire carrier chain dangling (mine has this problem,) muffler loose, remains of dead road kill stuck under truck.... Keep and open mind and look around.

 

U-joints and spline shaft slip yokes need to be greased. Otherwise, as Flamed said, look for loose mounts, etc.

 

i put the truck in gear today and pushed it back and forth, it sounded like the noise was coming from the rear end inside the pumpkin...what could it be??? should i change the oil in there?