Hello. We have a non turbo 4630 w/FWA and hydrostatic steering. When tractor is cold the steering wheel will not stop rotating at the 'stops' will just keep turning. After it is at operating temp it will rotate properly. But on a flat smooth surface, holding the steering wheel straight, the front wheels will drift off into a turn, it will not run straight for even a short distance. Anybody have any experence with these? Any guesses if it is steering cylinder or valve? Thanks in advance