severe bucking/stuttering when in gear

Hello,, it sounds like under load your engine is misfiring. Misfiring is usually due to spark or fuel delivery to your engine being disrupted. Hands on testing for engine performance is needed to find out what's going on. There is no amount of guessing anyone could give; just hands on testing with proper diagnostic equipment, workshop manual availability and a skilled and experienced technician is needed. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops