My 03 Sierra has code p0756 and seems to only have 3rd and reverse. 5.3 with cam,headers,tune,cai. Stock 4l60e and I think a stock converter. Picked truck up from the tuner after cam change and it drove good. No slipping felt. Ran it hard a few times then parked it and let it sit. A few hours later I took it for easy drive with the family and eventually only had 3rd and reverse. Code is for shift solinoid stuck open. Do you think I could change the solinoids and filter or do you think the trans is giving up. Truck put down 309hp and 305tq to the wheels.