help!

[ShoreMan]

ok so yesterday my dad calls me and he's pulled over on the side of the road with the truck off saying he has the stock trans guage pinned on h. (he doesnt have a trans gauge but he will soon!) we get there and i happened to have my friend who works at a ford dealership we had checked the fluid and it seemed fine and nothin burnt. i follow him home to make sure hes alright. the whole ride home hes on the phone with me giving me the play by play....the gauge would go up to h and drop back down to half and back up in a half second it sounds like. back and forth the whole time, tow haul would come on and off too.

today we let the truck run on flatter ground for about a half hour then checked trans fluid again. a little low. we fix it up and let it run for like another half hour to get the fluid cyclin. we take a 2 mile drive to the dump to see what time it opens tommorw. checked the gauge, fine. turned around head back and i hear O****!! the gauge had been pinned....again. i check the trans for mud(thats why mine was runnin hot recently) intercooler, radiator everything is spotless. we get home fine but hes freakin out cause he drives about 200 miles a day and needs the truck everyday.

ok so what are you guys thinking, trans never slipped at all as i think about it. its a 04 6.0 stock tranny 150k miles and we just bought it with 122K. its got a banks 6gun and a air raid intake if that helps anything. my friend who works for ford, his dad who works there and i all think hes just got a bad sensor on his tranny...yes no? help!