The Stovebolt Site Forums The Shop Area Driveline rumble noise when decelerating - help! - 500 mile trip tomorrow!

first off, sorry I've been out of here for so long, but very busy with work and the truck usually runs great
however: right now I have an issue. when I drive I'm good. Then I kick the clutch, get off the gas, and it sounds like I'm driving over a rumble strip.
I suspected my drive shaft park brake (1 ton) but I removed it, same deal.
No play in driveshaft, so no u-joints or center support.
In short: help!
I need to drive it on a 500 mile round trip tomorrow, leaving in 12 hours

When my truck did that, it was due to the rear end pinion nut backing off and allowing too much play in the gears. It wrecked the pinion and ring gears. Hopefully yours is something different.

Ed thanks you got me on the right track. Quickly disconnected the driveshaft at the rear end. the nut is securely in place, but my pinion bearing is definitely shot. and who know what else.
New question: will I wreck it if I drive 500 miles tomorrow??

Yes, change your plans

Unless you are looking to meet some new friends, I would fix the bearing before the trip.