Truck has 45,000 miles. Pristine condition. No towing,basically my Sunday truck. Tow my boat in Summer occasionally , 6,000 lbs. I drove the truck today on a 50 mile trip,no issues. When I got in the truck to return home, I went out and started the truck to let it warm up, 40 degrees outside. Let it sit there idling about 15 min. Then I put in reverse to back up and it was as I hadn't put in gear. I thought I had went to neutral. Had to get on throttle to get it to move. Finally started backing up but felt rough. Then went to drive and could not feel it go in to gear again. Had to give extra throttle again. Then engine light come on. Got on highway and it never shifted into overdrive. Indicator was showing 4th all way home. Tried to pull off from red light and it don't feel good! When I got home, pulled into garage, got out with truck still running and I can hear a slight rattle coming from transmission. I also hooked up my smarty to see what code and it shows, transmission control systems or something like that. I just did a transmission service on it about 3500 miles ago. I am scared this thing is gone and I know it will be big bucks to fix! Advice needed desperately ! Thanks in advance.