Transmission Solenoid problems of the 2000 GMC Sierra 1500

I've had several problems with the truck since I bought it 3 months ago. I've fixed almost all of them-abs was activating which was pushing me into traffic nearly causing a wreck so I changed the abs speed sensor and hub assembly. Front suspension was gone so I replaced that; as well as steering parts, brakes, the parking brake doesn't work, fixing it next. Oil sending unit, a/c belt and refrigerant replaced. The problems left are evap emission vent valve solenoid, throttle pedal position sensor, and random/ multiple cylinder misfire sometimes and cylinder 4 misfire other times. In 4x4 when it gets under a load something sounds like it's binding up and it pops but it still works. When I shift into drive or reverse or accelerate from a stop it has a shift feeling in the rear with a thump sound. Sometimes I can push the gas and it won't downshift to speed up when I'm on the hwy but that's probably the tpps. I just want my 4x4 working and my shift thump from a stop to go away. Help. In 4x4 the noise happens in fwd reverse and when turning and worse in 4lo but happens in 4hi and auto but not in 2hi.