518 short shifts and no od

Had this tranny built by local shop, it had been back to him twice and I've given up . Overdrive has yet to work, he thinks its something to do with the line pressures not allowing it to shift . Also it shifts out of 1st at 20mph even though I have shifter in first and it doesn't kickdown. It will stay in 1st if shifter is in 1st and pedal is mashed to floor, I played with the kickdown and it doesn't seem to make a difference. Can anyone help here? The guy said he would look at it next week but I think I'm better off figuring it out myself if its possible.