Hey Fred. In that 7400, with lift up in air, if you hit the lower button all the way real fast and let go, does the carriage lower a bit, or not move at all? If it doesnt respond to quick lift or lower commands, then adjust the Prop valve. (with forks up, disconnect one wire from prop, hold lower button, adjust prop with Allen key until carriage just starts to drop, turn opposite direction until carriage stops dropping, put lock nut and wire back on) Does the carriage respond very snappy now? If not, prop may be shot. Sol 3 could be stuck open too. It is beside Prop valve. Causes lift while reaching, slow lift with heavy loads. Check hyd filter for filings. If any are present, means free lift cyl cushions are in pieces. Do the free lift cyls cushion the last inch ok? If not, better take em apart and put heavy duty ones. There is 2 flow limiters, one in left free lift. other in right main lift. They rarely fail but get clogged with filings.
7400"s will make a tech go grey!