I'm trying to figure out a vibration problem that I've been fighting with for 3 months now. I think it was all started with bad tires but I think those caused another problem now. I thought it was still the tires and have continued taking it back to the tire place and they agree there is a vibration but are not convinced it is the tires. I'm not positive either as it is not constant. Sometimes worse than others and sometimes goes away for 30 seconds or so.
Anyhow, if I can put it 4wd and disconnect the rear drive shaft I can rule out the rear end and drive shaft. It only happens above 60mph unfortunately this is my daily driver which is mostly highway miles.

Let me know the best way to do this!

Have you checked any free movements in all 3 U-joints in the rear drive shaft? Specially in the rear-most one? If there is a free-play that it is.

I think you can completely remove the read drive shaft from the truck and drive on front wheels only in 4x4 mode.

I had the same problem and balanced the wheels twice and finally replaced the rear drive shaft and it now rides like a charm!

If your problem is with the drive shaft, I would recommend to get a low mile used TOYOTA OEM drive shaft. I replaced the U-joint in my drive shaft with NAPA U-joints and still had a minor vibration. I then replaced the entire drive shaft with a used TOYOTA shaft, and it rides like a baby... The shaft I bought had 315K miles! Probably someone maintained it through its life.

You will have to completely remove the driveshaft. There are 4 or 6 - 12 or 14mm bolts on either end of the shaft that attach it to the transfer case and rear axle. Steering will be very difficult in 4wd even with the rear shaft disconnected, so be prepared for that.

Four 14mm bolts by the pinion and four 14 mm bolts by the transfer case.

How in the world would by driveshaft go bad? I don't wheel this thing. Now, I must say, I've also not maintained and lubed the shaft and ujoints the way they should be and I have 200,000 miles on the thing so anything is possible. I don't think I would go with a junkyard drive shaft as you have no idea if that one is any better than what you already have. I'd rather find a rebuilt one or find someplace to rebuild and balance mine.
U joints are cheap so if that's the problem life is good but I'd like to try to narrow down the problem as this has gone on long enough. I've heard stories that there is a bearing in the transfer case that goes bad sometimes and lets the axle spin in an orbital shape that causes vibrations too. Hope that isn't the problem.

To be precise, on the transfer case there is a studded flange, and it is secured to the DS u-joint with 4 14mm nuts. They are not bolts. I just pulled my tranny, and I actually thought they were bolts, and wasted a lot of effort trying to turn heads that are actually the welded on (or maybe pressed on) stud heads. Just turn the nuts.

I assume the diff end is the same, but I didn't need to do that end.

I haven't seen it mentioned yet, so make sure your 4Runner is parked on a level surface, or on jackstands, before you remove the driveshaft.

More than one person has unbolted a driveshaft, only to then have the vehicle roll over them. Some with deadly consequences.

Tire vibrations and a driveshaft vibration generally have distinct characteristics, and should be easy for a Tech that's experienced in NVH (Noise, Vibration, Harshness) issues to diagnose.

U-joints go bad all the time and the vehicle does not need to be driven off road for it to happen. Heck, even a lowly 80's Volvo 240 will need u-joints if you put enough miles on it. Good news is it's cheap and easy to replace. That's my guess for the vibration.