While towing home a parts truck, I had a complete lack of power for going up hills... A few times the truck refused to shift into overdrive as well... I stopped and checked the k & N... it was a little dirty, but certainly not clogged or anything; Normally, this truck has plenty of get up and go and has no problem getting up to speed; After unhooking the parts truck, I took my truck for a drive, and she was back to her old self again... is this a sign of the transmission going south ?!?