i had that happen once i was coming up a bridge and when i went over a metal joint on the bridge i guess the wheels didnt grip it as well so the tod freaked for a second.. sounds like yours has had this problem more than once though.. id start with havin the transmission looked at since you had trouble with your trans leaking before... if you search for joe blacks how to on changing the transmission fluid (ATF) he shows where the fluid level check is located on the transmission, which is just a bolt, you could check that and see if its full as a first step