My 297c is having a arm and tilt drift problem. I have replaced the relief valves for lift and tilt. I have replaced the 4 check valves in the control valve also replaced the manual lowering valve. I have not repacked the cylinders since it was both lift and tilt I presume it is a valving problem. I have not replaced the main relief valve could it be it? The drift is the same with engine on or off. It does have the bucket leveling system and It has become very notchy when going up. It has started dropping down when you turn the key off.