i have a 1997 F-150 with a 4.6L im not sure what the trans is i think its the 4R70W or w/e and it has 121,000 miles on it and the trans fluid has nva been chaged. i was wonder if i should chage it or leave it. ive gotten about half and half opions. the trans fluid was low about 20,000 miles ago but it doesnt slip unless at WOT about 3 outta 10 times i do WOT it will slip and thats it.

 

My opinion? I'd do a complete change - drop the pan, clean it out, replace the filter, and drain the torque converter. Worst case, you will have to rebuild it anyway, the slipping is just going to finish killing it if you leave it alone.