Hey folks: I have a great running truck with 182k on it after I changed everything under the hood attached to the engine block. Lately though it has a rather consistent problem with the overdrive. When the truck is cold the tranny runs fine. After it's all warmed up, say an hour or so of back road driving. It will stop shifting into overdrive at 40 to 45 mph where it normally will. I can still get it to shift into overdrive if I accelerate the truck up to 55 to 60 mph, it will drop into overdrive, but If I hit any kind of hill to climb it will chatter or shudder the trunk as it wants to both stay in overdrive and try back down to 4th gear at the same time. Note: bought the truck with 157k and have never touched the tranny. I don't know about the fluid changes or if it ever had one. That I will do if the other problem can be fixed without major repair.