Hank,
Then you have to come over and visit. BBQ, beer and lying.
What time can I expect you?
Randy (Bakersfield CA)

I'll PM you my address so you can send the plane ticket.

I'd love to stop by next time I'm out there. Remind me, where's Bakersfield? My daughter is living in LA area right now.

Hank hit the nail on the head.I worked for GM as a tec for several years and will give you this advise.You said the u joints are tight and greased.That doesant mean they are good.You said its under torque when it happens so the first thing Id do is remove the drive shaft and remove the joint caps.Ive been bitten in the rear a few times being lazy.Remove the rear wheels and drums.Check the stud hols in wheels for damage or a cracked wheel.Also Ive seen this before.A crack in the flex plate if you have a auto.This most likly will not resonate to the rear but its good to check everything.You may hear the noise comming from where you think it is and its resonating through from where you would never think of looking.I had one before that made a banging noise under power and turned out to be loose/worn carrier bearings.This is something you wont find just by looking under the car or spinning the wheels on the lift.Another thing to check before tearing into it is the exaust.If its comming in contact anyplace you should see something.A broken dr side motor mount will cause exaust noise also.Bottom line is get a 12 pack and a good light to inspect everything.Good luck and keep us posted on what you find.

I bought all 8 Moog bushings and installing them tomorrow.
Hopefully that will solve this.
While on the rack, we will remove the drive shaft and check the u joints and motor mounts.
Thank you for your time and expertise. I appreciate it.

Randy

80 miles n/o LA, over the grapevine. Big mountain range between here and LA.
Welcome any time !!

Randy

Ok. Replaced all the bushings in the rear. Bang is still there.
Found the spot welds on the drivers side of the metal divider from trunk to cab, broken. Put 6 vise grips along that top edge. Bang still there. No reduction at all. Next is removing LR panel to see what's under there.
Aaaaarrrrrrgghhhh. I'll keep you posted.
Thanks
Randy.

Six welds broken and that wasn't it, wow. This is getting pretty interesting, I'm sure it's just getting aggravating for you. Good luck.

Found it.
S***
no laughing!!!!!

The bracket thingie that guides the parking brake cable inside the frame was upside down. It had been stuck for who knows how long. Then it came loose and flopped back under power. Under braking it would right itself but couldn't hit the frame because it was sliding over the cable. Took it off, righted it, and voilà ---- no more bang.
That only took three days on the rack and $400

So check your thingie if you have a bang

Thanks
Randy

Sorry Randy but I had to laugh a little. Glad you found it and it wasn't a major problem.

Did you need the 12 pack and flashlight to find it or just the 12 pack.Funny how in the end it always seems to be the simplest things you overlook.:)