Which is coming from under the seat portion of the truck. The other day I was chasing down another 1st gen up 6 miles of uphill twisty curves and as I hit each curve I felt this clunk underneath my seat. My 1st thought is the muffler, but that is solid and won't budge. It clunks at either a hard left or a hard right. Remember, this was going up a grade of twisty, snakey turns back and forth. No way I could replicate this noise turning either direction from a straight run of road. The forces of inertia is needed to cause the clunk. What is loose down there?

 

which truck?

 

If it's the 4X4 I suspect the shackle bushings.

Or maybe a flashlight under the seat.

 

Sorry, I should've mentioned. My W250 4 x 4 is the culprit. Hey, don't mean to hijack my own thread, but while you all are scratching your heads on this one, what would cause, on the same truck, a clunk noise which comes on when switching from forward to reverse? I was out hunting, and I had to turn around on this logging road. Back and forth from D to R to get turned around and the shift is so hard their is a definite clunk. I realize that an idle higher than spec could cause this, but I am only at 800 rpm's at idle. The truck runs like a dream especially with the addition of POD'S and STAN'S exhaust. Shifts awsome under load. It is only from a dead stop that the shifts get clunky hard. Am I just expecting more from a 4 x 4 or is this to be expected?

 

D to R sounds like a u-joint...

 

Usually a thunk from d to r is wear in the differential. Dave took care of that issue on his truck...maybe even did a writeup?....As for the clunk, yeah, on a 4x4 I would suspect shackle bushings. I know mine are shot and I get the same noise through the twisties...thought it was cab mounts but that's the one solid thing on my truck, as it turns out

 

I have the same problem except if i just crank the wheel all the way left or all the way right it will clunk. Weird thing is it doesn't happen every time i do it, maybe 75% of the time. Anyway least you are not alone...lol...