Truck starts bucking for no reason when I push on throttle it will gain speed and bucking stops. this is only at a constant speed that this happens.

Run fault codes and look for MAF/MAP and throttle position sensor problems.

If the idle speed is not steady, you could have a sticking idle speed control valve, or a dirty throttle body.

Problem with electronic throttle control maybe. Any light's lit on the instrument cluster or messages engine power reduced . Could be a sign a position sensor is going bad . The gas pedal assembly has to sensors as does the throttle body . You could try cleaning the throttle body bore . Having a qualified repair shop hook up a diagnostic scan tool to view sensor data would be a good thing .
007 Idle Speed Problems Scan Data for Idle
1 reason your cars throttle body needs cleaning Gain lost horsepower and...

You may check the Air sensor on the engine.

Check the throttle cable need to be adjusted, if your check engine light is on maybe throttle position sensor is bad. maybe engine needs a tune up or it could be the engine is on it's way.

This could be a clogged air filter and /or fuel filter. start there. Also a dirty throttle body can cause this. Use brake clean to clean this. you only need to clean the inside of the throttle body , use a small brush and clean as far as it will reach, also clean the back of the plate. Start it (might take a minute) and spray the brake clean into the throttle at higher rpm's.

This can be caused by a faulty throttle position sensor (TPS). It will normally be found on the end of the throttle shaft oposite the cable connection. They are fairly simple to replace, and cost less than $50.

More then likely you have a faulty throttle position sensor (TPS)

check the module and coil pack in the distributor

its your cluster it happened to me went to a junk yard paid 50 bucks for a used cluster now its working now i know how fast im going. i hopes this helps u