Alright, straight to the point: when i am in decel after letting off the gas over 20mph I have a vibration that has gotten worse in the last week. I tried decel in neutral and 4wdH decel, as well as decel while turning left and right. No difference. I am sure it is not my brakes (such as a bad caliper) because if I hold the brakes with my left foot and gas with the right I get no vibe. My wheeels are clean and I am waiting for my truck to get out of the shop with new tires right now, but im sure thats notbthe problem because it doesn't happen as long as I apply even the smallest amount of throttle.

Things my search has led me to check out:
U-joints (check while unbolted from diff) and regrease if possible
Driveshaft flange bolts
Pinion nut? Where is that? Please excuse my noobiness. It sounds like its in the transfer case? I'm used to AWD drivetrains with an electronic center diff.
Front CVs not aligned. My truck does have th. Torsion bars cranked by the previous owner but I drove it for a month without this problem. I DID just work on the CV axles. Pulled one off, rebuilt it (90% sure the tripod joint went back in the right spot... my mark washed off) after that I said screw it and ran into town for a brand new axle for the passenger sise to save me the headache.

I will have access to my fathers garage next week and want to get a quick list so I can get to work on it right away. I tried to crank down the torsion bars to stock last time but the bolts were seized up. I put CLP on them but couldn't get them to turn before I ran out of time. Now that they have soaked for a week they will hopefully move, or I will just get some new bolts from toyota.

Before you jump to the same conclusion I did... the vibration was there before I messed with the CVs. It slowly got worse before and after so I believe it is a coincidence.

Thanks in advance for any help, it is as always appreciated.

 

Possibly a wheel bearing?

 

A wheel bearing would be felt during accel and decel..

Just put the rear on jacks and rotate the tire/axle and see if you feel anything out of the ordinary there. Look for looseness in any of the directions of motion that is out of tolerance and looseness for parts that aren't supposed to move. repeat same for front. It's an easy and free test and will eliminate a few parts as being the issues if nothing else.

Do you htink it's coming from rear or front?

 

The pinion nut holds your pinion gear in place, if that is loose it could cause vibration, just as you're letting the gas off. The nut is held in place by tightening it and using a chisel to punch it into the keyed out shaft, I've used an old nut before when changing a seal and had it come loose. Just something else to check, you can tell by checking the end play at the flange, easy to remove your driveshaft and check it out, and easy to change the seal and install a new nut if you have too.

 

Push up real good on the front U-joint and see if there is any play from the trans output shaft.

Check that all driveshaft grease fittings line up.

 

the cv's shouldn't be turning if the hubs are unlocked, and everything is in 2wd? if so, they shouldn't be a factor.

if the driveshaft is out of balance, or the rear pinion flange/trans flange aren't parallel, you'll get a vibration on deceleration.

get one of those cheap harbor freight protractors, you can compare the flange angles with it, you don't even have to pull the driveshaft to do it.

 

I had a decel vibration that plagued me for about a year. Pulled the drive shaft and the front u-joint was very stiff in one direction. Had my machine shop replace it for about $70.
Mine only happened over 55 mph or so. Its much better now.