I've recently picked up a '99 SR4 TRD with 109 K on it that has an automatic transmission. I haven't driven Toyota 4wd's before, and the drive train is making a "slapping/bumping" noise like that of an old U-joint going out in older pickups. and I don't know if it's normal or if it needs to be looked at (I do have a 30 day drivetrain warranty, so I want to act fast). When driving down road, if I let off the gas pedal slowly there is no "bump" or "slap", but if I let off fast you can hear it and feel it. Sometimes, it also happens from a dead stop when I push down on the gas there is a "bump" sound/feeling. The problem, if any, doesn't seem to be in the transmission but somewhere in the drivetrain. I hope this is descriptive enough for someone to offer an opion, and thanks in advance for any suggestions.