Over the past few months i have been having a vibration issue with my 4runner. It was a high frequency vibration similar to a u-joint and could be felt mostly in the steering wheel to the rear end. The driveshaft was inspected and greased u joints were fine but the vibration would not go away.A few days ago while coasting to a stop i heard a grinding noise from the rear end and realised that the rear wheel bearing was trashed. I had changed them 2 years ago...why did they fail? Well before i installed them i carefully removed the seal from the bearing and packed it with some extra grease. When i removed the failed bearing the seal had popped off likely from pressure from the extra grease. then my water crossings and ocasional mud bath did not do too well for it. I have had wheel bearings for years without a failure before i tried to pack extra grease in them..I replaced the bearing last night and boy oh boy...the vibration went away...Just for your info...HIGH FREQUENCY VIBRATIONS..MAY NOT NECESSARILY BE A BAD DRIVE SHAFT...CHECK YOUR WHEEL BEARINGS.

 

At what speed did you start feeling the vibrations? I have a similar issue whenever I go past 80mph

 

Vibration started around 20 -70 MPH...Above this it started to smooth out. Disconnect your rear driveshaft and go for a spin on the road to see if your vibration goes away. If you have cranked your torsion bars up you could get vibration from the front too. If you have freewheel hubs you could isolate the front drive train vibration. Look behind your rear wheels for oil leaks or sweating behind the drum housing. Smell for gear oil. Find a clear road accelerate to about 30 MPH and switch off the engine ..coast and listen for clunking and grinding..be carefull not to lock the steering wheel when doing this...use a straight road...lastly put the rear tires in front..could be Tire problem...tire problems tho are usually a wobble, shimmy or a bump hopping..Vibrations are usually drive train..Shafts or bearings.