Yeah, bed mounts. Sorry, wasn't real clear there. :D Spring mounts and such as well. Anything that could possible generate the noise.

uncertain
 

it feels like the shaft is slamming back on u joint when hitting gas and pulling away from u joint when braking? does that make sense? is that possible? i know theres always vibration in the floor i have a flowmaster dual exhaust though.
I'm just trying to explain this the best way that i can.
does that sound like bad u joints or a whole drive shaft problem?

Thats very common behavior coming from a neglected U-joint. They will just keep workin even after the needle bearings are long gone, and only ever give you those subtle side effects. Replace 'em, they are cheap and easy to do.

The OP's issue is exactly what was wrong with the front u-joint of the driveshaft of my truck. There was a "thunk" sound upon take-off and sometimes when slowing or braking. The cap was broken and every needle bearing was missing, thus allowing it to "flop" around.

http://i160.photobucket.com/albums/t...e/100_2420.jpg

Word to the wise -- pay the extra $10 and buy the American made u-joints instead of the Chinese made garbage. I accidentally had purchased one American made and one Chinese, and the Chinese was 0.010 too large and wouldn't fit the yoke.

thank you soo much. I'm having it fixed monday.

So the alignment is done and it runs smooth. The u joint wasn't the culprit. its the spider gears on the rear end. The mechanic said not to worry about it unless it gets really bad.

Spiders are cheap, but are definately a step up from u-joint replacement. Find a buddy who knows his stuff and you could knock it out in a couple hours.

My friend's '86 had a bad ujoint in the rear of the rear driveline, and in the cv joint up front when he bought it. Every time he put it in gear (4 spd manual) or shifted it made a big 'ol CLANK! and in 4x4 it made the same noise with every rotation of the driveshaft. Needless to say they got replaced shortly. Then he blew his front spiders in a mudhole.

I get the clank drifting down the hill when it shifts into 2.

Drifting? You should post a video ;)