larry hatfield

I have a 1992 cadillac coupe deville, 95K mi., with 4T60 transmission. It won't shift automatically, must shift manually. Does not have 1st gear or overdrive. Runs strong in 2nd and 3rd, no slippage. Clutches and torque converter seem good. Could it be an electrical issue or mechanical? Transmission shop guys just say through $2500 to $4000 at me and we'll fix it with no explanation of what their fixing.