I have been having this issue these past couple of weeks that is hard for me to explain. The best way to explain is the vehicle sounds and feels like it cannot decide what gear it should be in. When i try to maintain it at 35 MPH it jumps to a gear than drops back and does this several times until i accelerate. It seems that it happens randomly but often times when i go uphill or continue from a stop position. I have replaced the distributor cap and rotor along with the fuel and transmission filter with new transmission fluid. The spark plugs are a year old. My exhaust is almost non-existent if that matters. It almost feels like it takes more gas to accelerate. Maybe somebody has run into this problem before. If so, could you help? I seem to fix one problem then run into the next.

 

First step is to tell everyone what you are driving. year, engine, 4wd or 2wd, etc.

 

year is 1987 engine is 5.7 its throttle body injection 4 speed automatic transmission its 4wd it has overdrive

 

I hope someone else will be here soon to give you their seasoned advice. I am pretty new at this- however, I guarantee they're gonna ask for codes so do you have a CEL? The things that pop in my mind when I read about your "erratic" shifting are TPS and Torque Converter.