I thought I would post what I found was causing my problem.
I assumed my U-joints were bad, as it sounded just like that... coasting I could hear the clunck-clunck-clunck that slowed down in sync to the car slowing down.
(acceleration I could not hear or feel anything, loud muffler)

Well, my problem was simple... I had lost 3 of my 5 lug nuts and one of the remaining 2 were not tight.

I replaced and torqued them, problem solved.

But my question is, has anyone else had this happen? I remove lug nuts with a battery operated impact gun, but ALWAYS torque with a torque wrench. These lug nuts are 'gorilla' that need the special key so I don't think someone tried to take them off. there were no scratches or marks on them, and no other were loose (I re-torqued all of them)

I've been at this a long time, and nobody I talked to has had something like this. Yes, people say they come off if you don't tighten them, but not 'by themselves'

 

The only time had anything like that happen was when I was moving from AZ to IL and I had a 78 Grand Prix and I was towing a 69 Roadrunner with a tow bar. Right around St.Louis I heard some clicking on braking and acceleration and didn't know where it was coming from. Well I got as far as Joliet, IL and took an off ramp and my front driver's side wheel fell off, munched the fender, and rolled into a gully. The whole train skidded to a stop on the brake disk, and upon inspection, I found that the studs were all sheared off. I retrieved the wheel, which was ruined having been slotted at the lug holes. Not sure what lesson I learned,that time, but, obviously, I didn't tighten that wheel correctly last time I rotated the tires. I've been using an impacter to loosen lugs and a torque wrench to tighten lugs for the past 25 years and never had a problem, so I just chalk that up to bad mechanicing or other cosmic interference.