96 Tacoma Drivetrain
 

Lately when going from P to R, P to D, D to R, my truck has a "jolt" intermittently and now there is a squealing that I feel is coming from the drive train. It gets louder while accelerating and seems to grow quieter under deceleration and go away completely at high speed (50+). It isn't belts or brakes i definitely know those sounds. I am thinking U-Joints or the Center Carrier Bearing. The transmission fluid looked good as did the rear end fluid so I am just assuming again that it is an issue between the 2 aka drive shaft area. Also when I took the plug out of my rear end to check the fluid level there seemed to be some air pressure built up inside. There is a plug in the top of the rear end where I would normally believe a vent of some type would be but am not sure if this is normal for off road usage to prevent water from getting inside. Thanks guys I'm new here and glad to have found this site.

Take a look at your center support bearing. Unbolt it and let your driveline hang down, then spin it by hand. It should be pretty obvious right off the bat what the problem is.

As for the pressure in the rear, sounds like the vent has failed. Its supposed to allow air out, but stop crap from getting it. Its basically an open vent. If its plugged, it can build up pressure and force oil out your seals down the axle tubes.

What am I looking for with the center support bearing? excess play in the rubber? hard to spin the bearing itself? If the center bearing is fine should i just throw all new u-joints at it?

Excess play, or a very hard to turn bearing.

I would consider taking the driveline to a shop for a proper balance and inspection.