You can use DEXRON II, or FORD type F automatic transmission fluid in your power steering,( it will keep the seals in the pump from wearing out prematurely )......Check the transmission fluid on the dipstick,If it is dark brown, or smells BURNED, and seems to be dirty looking, You might want to have the fluid and trans filter changed,Dont forget to drain the old fluid from the Torque converter as well....That should help with the shifting problem,....Usually HIGH MILEAGE automobiles with automatic overdrive transmissions are prone to that shifting problem in colder climates, if the problem gets worse , Have the transmission overhauled.