ok so like the title says it wont shift when it is warm, when it is cold it shifts just fine untill about 30 mins of driving. Then it will start to slam in gear and then it will get sorta stuck in 3rd. The only way to get it out is to shift it into second but then it wont go into first, and also it wont go into overdrive, it is a 5.7 vortec with a flat pan tranny and i have changed the fluid and the filter so far and dont know where to go from there please help asap