major clunk - driveline ?

I would appreciate anyones help with this problem. Just recently this clunk started, timing is strange since I just replaced leaking oil lines and gunk't-out the under carriage. Now the truck clunks from start off. I first thought it was bushings in the front because that was the focus of the cleaning and the sound but it seems to be getting louder as if something will snap. I had a friend drive up a hill, jerking the truck and the noise seems to come first from rear and then the front so I believe it could be any part of the driveline to other suspension components. Does anyone have any advice ?? My truck is a 98 4X4 with 82,000 miles, located in Denver.

Thanks

I'd start out by putting the parking brake on and truck in neutral not running.
Then slide under and grab the drive shaft and wiggle/turn and watch both universal joints for play also looking for rust weeping out of it. Check both shafts.
Maybe take a close look at the motor and transmission mounts.
Bob B

Thanks Bob,
It seems the u-joints are okay. THe tranny/engine mounts sound like a possibility. How can you check these ? replace them would be one way but I believe that is a big job, no ?
I greased everything under the truck, all the rubber and joints. Still no avail. It almost sounds like a faulty shock. I have been reading on this forum and notice a lot of owners have noise problems. It's almost like a electrical problem, what do you think...it can be anything !
I thought pehaps it was the leaf springs, i sprayed them down good with wd40.
I do appreciate the reply.
Thanks

This might be your problem, It solved my chirping/clunking problem. Good luck.

this site explains some clunking noises.

http://www.startribune.com/viewers/story.php?template=print_a&story=3856014 (http://www.startribune.com/viewers/story.php?template=print_a&story=3856014)

my 2000 gmc sierra would make a thunk/clunk when starting up from a stop. i put in a new "nickel plated" slip yoke ($139.00 wholesale) with recommended grease ($33.00) and the problem has been sovled for 2 years now. a buddy and i did the install so total cost was under $175.00. i bet the dealership would charge at least $600 for parts and labor.

I had the clunk noise coming from the slip yoke after a new transmission was put in. I noticed it most when I would stop hard at a changing red light, it would clunk when I released the brake to proceed. I pulled the driveshaft and greased the splines, never heard it again.

James

I had this same problem with my 2002 Sierra. I had to remove the driveshaft and put synthetic grease on the yolk that slips into the tranny. Make sure it is clean first. Make sure the splines are lined up properly or you will go through alot of u-joints. That fixed my problem, maybe it will fix yours.