It sounds like you may have an ignition problem causing a misfire so the first place I would start is to look at the ignition components such as spart plugs, plug wires, and definately check the coil terminals where the spark plug wires connect to as this is a very common area for rust and corrosion. If you have access to a scan tool it will show individual cylinder misfire. If everything checks out good here then I would look at transmission data-pending you have access to a scan tool- and watch TCC apply% and TCC slippage rpm and see what is going on when you feel the bucking, but again I would really lean towards an ignition problem or at least rule it out first.
