my truck is a 4.2L v6 engine, would somebody please help me explain why my truck when it starts, it feels like normal, but once i change gears the truck starts trembling. I have already changed the serpentine belt (it tore), new oil change, and new fuel filter (since i thought that was the problem) but nothing helps. i ran a diagnostic, and says that both air sensors are defective, but I just want a second opinion as to what is causing that trembling when i accelerate. my second guess was the transmission, but it doesn't jump gears. any help is well appreciated, thank you.

 

Please give mileage and exact code numbers. With the code numbers, we can more accurately research the problem. Some places tell you what the problem is because they want to sell parts. So please post the code numbers. Thanks