I have a 1997 4Runner SR5 2WD. As of the past few months, I've been experiencing an odd problem. At times, especially when cold, when I put the truck in any forward gear, when I push the accelerator, the truck does not more, the engine seems to race under load. I push the accelerator to higher rpms, then a loud and jarring "clunk" is heard from the drive train, then the truck begins to move forward. The clunk feels as if someone hit you from behind at about 20mph. It does not happen in reverse and usually goes away after the car is driven a hundred feet or so. I have experienced this at stop lights after driving for a distance, but much less clunky.
I have also had some cold issues with the transmission in reverse. See this thread:
Thanks,
Brian