I picked up the Lucas Transmission Stop Slip fluid this morning for $9. I had the extra ATF so I did drained the pan and refilled it. I added the Lucas first, then two quarts of ATF. The initial test drive was about 20 miles of mixed city and country road driving. So far I will have to say I am impressed with the difference. I did not "feel" a real difference but the temps stayed at 180 or less the entire time. Previously it would shoot over 200 degrees when under hard acceleration or coasting to a red light from any speed. This time the trans slowed the 4Runner down like it should without spiking the temp so fast I could watch the gauge move like the RPM gauge.
This is just the first few miles so I will keep an eye on how well it continues to work over the next few weeks. So far I am impressed though.