I began to notice that when the truck is cold.

I began to notice that when the truck is cold, it has to warm to normal temp before trying to engage in gear. If not, it will do a hard jerk into gear after sitting in what feels like neutral for a few minutes. It drive great, but shudders when driving at almost any speed especially when speeding up. Loss of acceleration, and check engine light comes on and off. Sometimes now when I sit at a long red light or train tracks, the engine temp raises to 3/4 hot and when I begin to move, it almost immediately goes back to normal. SOMETIMES I can smell burning coolant. Had engine codes read, suggested O2 sensor, catalytic converter, torque converter sylinoid(sp?) Among other things. Someone told me to check the transmission fluid-was really low. Added some and it helped. Going to have the transmission fliter changed.