Well, there seems to be no consistency to it. I can't reproduce the
condition on command.
Just say I'm driving down the road and giving it enough gas to put a
load on the drivetrain. Sometimes when I let off, I get the noise and
vibration. It literally sounds like someone dropping a few machine
screws into a set of turning gears. It's loud, and there's a good deal
of vibration. The whole event starts and ends in less than a second.
It's a very short but noticeable burst of noise and vibration.
I tried to make it happen yesterday... going from acceleration to
letting off completely, sometimes slamming the brakes. Tried
accelerating and letting off in the middle of a curve at different
speeds, sometimes braking as well--no luck.
Also, I didn't mention, when putting it in gear, or going from reverse
to drive or vice versa, there's a pretty loud bang. Me and a buddy
took turns watching the driveshaft while changing gears in his
driveway. You could see it move and then stop violently. Also, if
you're driving with the drivetrain under load, and release the gas
suddenly, you hear a slight bang...more like a loud thump. And then it
happens again if you give it gas while coasting if the drivetrain is
NOT under load. You gotta ease back into the gas to keep that from
happening. It sucks when you're on the interstate and some idiot hits
the brakes at 80mph. You suddenly let off the gas and BANG!
It just seems there's always been a good deal of slack in the
drivetrain--at least as long as I've owned the truck (since September