I am having two problems. The first of these is that when the car is in reverse, while reversing there is a squeeking noise (only in reverse though). The second is that at idle, the car no longer moves foward on its own and when gas is applied the car kind of leaps foward. I had the transmission fluid changed about 3k mi ago and have been told that if the place that changed it flushed my tranny that can permanently damage it and be causing these problems. Is this true and do ya'll think this is what my problem is? Any advice would be much appreciated.

Specs:
99 4 Runner Limited 2wd
83k mi

 

Sounds like low on fluid. My old Mercedes diesel was just doing the same thing. I just put a new water pump in it and after disconnecting the trans. cooler lines at the radiator and losing a bit of trans. fluid, I noticed the same symtoms, weird noise and engaging only when applying throttle. It was exactly 1 qt. low, with the trans. fully warmed up, it was off the dip stick low, added 1qt and level was normal and trans. is perfect now.
I know on my wife's Honda CRV you have to use Honda trans. fluid or you end up with a hard shifting problem within a couple thousand miles. Does your Toyota manual talk about using only a certain type fluid, is that what was used on that last service?
May not be the issue with you but hope so. Good luck. If it's not one of those issues and you don't have extremely high mileage, I'd go back to the shop and see what they want to do about it.