I currently have the "wobble wobble wobble" and some days its better or worse, one minutes its better or worse. Likely the wheel/tires even though ive had it balanced every which way by numerous shops.

I had a U-joint develop a hair line fracture which was noticeable around 40-ish mph and was bad enough above that that I WOULD NOT drive faster than 35 to get home. It literally felt like Godzilla was chasing me down the street is shook/vibrated so bad.

Do as they said and spin the driveshaft. grab a light and inspect closely as even the smallest defect in a part spinning that fast will cause a big upset in the driveline. If nothing is seen, you can also remove one driveshaft or the other and test in 2wd/4wd to determine if it the rear or front DS.

A factor commonly overlooked is that balance is not always the cause of your bad tire/wheel creating a wobble. Shape is most often the bigger problem. You can mount a square wheel on a balancer and achieve a balanced wheel, but try driving on it. Match mounting can help, but sometimes the tire is just a big ol' smokin' turd.

When I bought my 4runner, I had the same problem. Got new tires a few days later and it went away. Tires may need to be changed, however, it could also be your bearings. Lift the truck and shake the tires and see how much play there is in the bearings.

It was tires not balanced correctly on mine. A regular tire shop doing regular balancing can do a good job if they choose to. Many shops get within 1/4 oz and call it good. That may work okay or at least not that noticeable on the back but on the front it can go right through the front end parts to the steering wheel. Just happened to me. Rotated the wheels front to back and the steering stopped shaking. Took it back and had them re-balance the wheels I paid good money to have balanced right the first time. The road balancing thing is probably more precise but a good standard balance, IMHO, should be adequate for these rigs. They aren't Ferrari's or GT40's. Saw the movie over the weekend. Good stuff!

Also had a small bit of play in my rear u-joint which caused a kind of low roar. Driveshaft shop said I needed a new driveshaft too because it was .040 out of being straight. A PO had dropped it to flat tow the rig. Literally dropped it on the asphalt which apparently can be enough to put that ever-so-slight bend in it. I kept the driveshaft. If the one in my 98 goes bad I may just put it in it with new u-joints and see if I really did need to buy a new driveshaft or if I just needed new u-joints. I've had bad luck with shops in my smallish town. They talk the talk but they can't walk the walk or they are simply trying to con their customers. I think it's probably more of a con than anything else. I think they know better. I'm running at about 50% good; 50% bad.

Before I did anything I'd rotate the tires front to rear and see if the vibration moves to the steering wheel. If it does you have a tire out of balance. I'd then remove the rear driveshaft and drive it in 4wd. The two things will go a long way toward narrowing down the issue.

To what extent would you say? Would any movement up/down be bad?

I'm curious, I checked that and it had some up/down movement and I took it to a friend to look at and he said its fine, a little movement is okay. He's a lead mechanic in a heavy diesel shop so I'm pretty confident he knows what he is talking about.

I feel like he actually may be wrong in this case and the output shaft bearing is bad and that's what is causing my vibration

Mine has 3/8" up/down. Way too much, IMO - mimics a bad u-joint

There should be zero play in the TC output (same with the diff pinion input). They are both riding on pre-loaded bearings.

(there will be some play in rotation - that is normal)

-Charlie