[KPerson]

For the second time in a month my truck has shifted out of overdrive while I have been passing someone with the truck at WOT.
I wait for it to shift into overdrive and it dosent, I notice that my light is on on the O/D off switch. Is this a TPS issue or a temp. sensor. The truck is unloaded and it's only 60degrees here. I dont know where to start. Once I push the O/D button everything goes back to normal.

I have changed to a synthetic ATF, but I cant see that being the problem..


Thanks
Kurt