drive shaft?

99 sierra 4.8 - "clunking" coming from rear end when put into gear ... also does it when shifting at low speed .....u joint? ANYBODY????

I too get a clunk when I put the tranny in gear. If its like a whinning noise when your moving more than likely its a u joint. With a jack pick up the back diff lifting the tires off the ground, chock ur front tires and put in drive letting the tires spin freely. You'll see if its the u joints.

I too get a clunk when I put the tranny in gear. If its like a whinning noise when your moving more than likely its a u joint. With a jack pick up the back diff lifting the tires off the ground, chock ur front tires and put in drive letting the tires spin freely. You'll see if its the u joints.
............. so what will the joint do if it does need replacing ? , what should I be looking for ? I appreciate the advice , but getting under the truck while the tires are spinning with the truck truck running sounds a little dangerous , but I'll do it anyways .... probably .

known problem with gm trucks. gm fix is to pull out drive shaft and put some special grease in the slip spline. they did this to my truck and the clunking was gone.