2009 tacoma shakes

so I have one that has my buddy who is a mechanic and myself kinda stumped. When I accelerate at a decent pace between 24-29 mph and 31-34 mph with rpms at 1600 the truck will rattle. I'm going from 2nd to 3rd and 3rd to 4th gear. It will shift at 1800 rpm so there is a little space where the truck quits shaking then shifts. It felt like from the back right away but I'm starting to second guess that.

So here is what I did, the recall for the rear leaf springs got replaced. I heard there is a mod for that due to some shaking.
I replaced rear end fluid, it has the anti friction in there. We replaced the middle u joint in the drive shaft. The others are fine. Did a coolant flush. Front bearings and shocks were done last year. Brakes and rotors were just done.
So we took the drive shaft off and put it in 4wd it still shakes. So we put it back on and it will shake in 2wd and 4wd. We had scan tools on it, my buddy doesn't think it's the tranny but u never know I guess. Any ideas or has anyone else experienced this? Thanks!

 

Btt

 

That's weird one retorque the rear leaf springs/anything that was replaced , possible tires need to be rebalanced.

 

"The FSM is wrong it is not 37*lbf but 73*lbf."