Hello...Had a vibration and thought it was the center support bearing....When they put the drive shaft back on the vibration was still there. So I have been driving with the 4WD on with the front only pulling and now it has been actually disengaging while driving. So I am in the market for a balanced drive shaft or an explanation on why the front diff is disengaging...

 

When you say, THEY put the drive shaft back on, was that after replacing U-joints and checking the shaft out? Any drive shaft shop should be able to tell you if it's bent and rebalance the drive shaft.
Did the vibration stop with the rear shaft out? Does it matter if you step on the clutch? Accelerating vs coasting? Do you get a vibration in neutral or only at speed? Does it vary at different speeds?

As far as the front disengaging, Is the transfer case shifter popping out of gear or locking hubs not staying engaged? The stock detent springs for the T-case shift rails might need to be replaced. Some people put the heavy duty springs from Marlin Crawler or Trail Gear in. Locking hubs can not fully engage or engage at all if they haven't been service in a long time. Old grease gets thick and nasty and the hub dials might turn but the gears won't engage. Or if they do engage, might take a while to disengage. Service your hubs if you don't know the last time they were done.

Take a look at your T-case mount and your engine mounts and make sure they are ok. Sometimes they LOOK ok so use a bar or something to pry with. Maybe you already know all this. Just throwing out ideas in case you don't.

Nice truck by the way.

 

The shop I use is an import shop and the owner has a llot of experience in older Toyotas They put on the center support bearing as I just didn’t have time to do it. After remounting the shaft there was still vibration and. he said that the yoke on the diff was actually moving out a little bit. Don’t know what to think about that. So. He left it for me to drive in front wheel drive. I drove several miles on Saturday and no issues. Then on Monday driving to work is when it surprised me. It has automatic locking hubs and when it goes out of pulling there is no clicking as they are still engaged. Just driving along and no go, but I’d did notice one thing , that the speedometer went to like 65 or so. And when I slow down I can regain pull power again. Sort of intermittent. Thinking about finding a drive shaft shop to check balance and see it it is out, but there i nothing that has happened to the shaft that I know of. I bought the truck new.

 

The flange on the diff moving could be a problem depending on how much movement and how it moves. A small amount of back lash is normal. If the nut is loose it needs a closer look. That nut against the crush sleeve sets the pinion bearing preload. Is the seal leaking? If the rear diff oil hasn't been changed in a long time, now is a good time to drain it and check for excessive metal. If none found, that's a good sign and you will have fresh oil.

Were the U-joints ok? A loose one is obvious but a siezed one can cause a vibration too. Often overlooked because they are not sloppy or clunky. Make sure the splined section of the drive shaft is not sloppy or over greased. Some of them won't allow the excessive grease to escape and put the shaft into a bind. Also make sure the U-joints are in phase if the shaft has ever been pulled apart.

I never had automatic locking front hubs on a Toyota so I don't know their quirks. I have had them on a Chevy and they were inconsistent. Wouldn't engage or disengage at times. I installed manual locking hubs after that.
If your transfer case is not popping out of 4WD, I would be taking a closer look at the hubs.

I've had an axle bearing fail after many miles but that was more of a rumble than a vibration.

I've had drive shaft vibration after lifting my truck because of the pinion angle but it doesn't look like you lifted yours.

Tire balance is good?

That's everything I can think of to check. Did the vibration just suddenly happen or after some work was done?

 

The truck is not lifted. Stock except for a little larger tires. Tires not the issue. I talked to my mechanic this afternoon and when they put the drive shaft back on there is a vibration Took it back off, no vibration. There is Carolina Drive line in Spartanburg, SC and I can send the drive shaft there’s and they will check it to see if there is a problem. And they can balance if necessary. I will inspect the shaft this weekend, universals and all May even mount and get a feel myself how bad the vibration is.. I have something else to drive in the meantime….

 

Looks like fun. I've always had fast motorcycles and 4WD's. Only car I ever had, I repo'd from one of my kids. A 66 Mustang. Another kid totaled it. Good luck with your truck. Please follow up with the fix.