If you lose all drive after 5 minutes including reverse then the filter is clogged with debris from failed/worn part/s. If it goes 1-2-3, then freewheels, then it is the end clutch that is shot. You mention the computer. Unplug harness that goes to front of box 4 wires. this will give you 3rd -no solenoids working.
mags, February 2010