I have an '01 4runner with 120K. I haven't driven it in a couple weeks and started it up yesterday and when I put it into drive and pressed the accelerator the engine revved but tranny didn't engage. I put my foot back on the brake and waited a few seconds and the transmission engaged. I checked fluid, looks and smells ok (no burning smell, bright red) What's going on? Thanks!

 

Was the fluid level okay? Maybe since it had sat for a while it just needed a few extra seconds to pump everything through.

 

When is the last time you checked your rear brakes? It sounds like they may be sticking, hopefully not because of leaking inner seals....

 

I also have an '01 4Runner. I am a bit paranoid about things right now, since I just had a milkshake this past weekend. What you describe is very similar to what mine was doing when it started spewing the milkshake. Keep an eye on the color of the fluid in your coolant tank, and see if it ever overflows.

It doesn't help that you are at the mileage to start worrying about the radiator going out (i.e., milkshake). There are several recently active threads that are talking about this that you can look into.

 

Most of the milkshake threads I've seen have stated 160k-190k for when their leaks started to happen. It could be a small leak though, as opposed to the complete failure of the seal which is when it usually gets noticed. If you're that concerned about it, just get an external tranny cooler and cap off the radiator outlets, but it could be something totally benign like kball said.