Drivetrain Vibration: Please Ring-in before I go to Dealer

[trulli3300]

I've got a drivetrain vibration, only occurs when I'm on the gas. Here are the clues:
1. goes away completely when I take my foot off of the accelerator. 2. No vibration in neutral. 3. no noises parked or driving. 4. reduced slightly when in 4WD. 5. Creates a slight and fast "shuddering" in the car most noticeable between 25mph and 55mph. 6. slowly getting worse - within a weeks worth of driving.

The Runner has 200k miles on transmission. Its a '99 LTD with push button 4WD. I have already gone through pink milkshake last year(what a horror). Trans fluid and coolant are what they should be. The trans shifts as smooth as ever. Is it possible it may be a transmission mounting? Is it possible it is a failing U-joint even though there is not clicking or ticking when engaged? Is it the planetary gears in rear axle(no whining)? I will get under the car this weekend but I need some clues as to what to look for.

This thread is linked to my phone so I can respond more quickly if you have any questions or answers that can help. Thanks.

 

[Elton H]

im goin with u joint park it on a flat surface and rock it back and forth it should clunk if its bad

 

[trulli3300]

@Elton

Thanks, there's an idea. Although I'm just a little guy. By the miles I drive now, I only have it the U-joints lubed once a year. I do my own oil changes. Its possible there is some worn-in free play that my have become too much. I am hoping this is all it is.

 

[JohnsD90]

Thanks, there's an idea. Although I'm just a little guy. By the miles I drive now, I only have it the U-joints lubed once a year. I do my own oil changes. Its possible there is some worn-in free play that my have become too much. I am hoping this is all it is.

A bad u-joint causes a lot of vibration for the size part it is, it created an uncomfortable vibration at highway speed, and it got so bad i finally changed it and it felt so nice to drive a smooth 4runner again.

 

[Kurtis]

x3 on the U-joint. Just grab that booger near the U-joint and wiggle it. I shouldn't move. If it does...get a new one. When you install the new make sure the caps are tapped out a bit to let in the grease. U-joints often fail because some ding dong didn't leave enough room for the grease to get into the caps and bearings.