Swoop- that's exactly what I'm saying- thanks very much for the input- I've never had one of those valves go bad before & wasn't sure of the symptoms- I didn't want to go on a hunting expedition on my customers dime without having a direction- I couldn't think of what else woulde cause those types of symptoms.

john j- thanks very much for the lead-my local dealer was of no help when I couldn't find the stamped #'s. I always like to verify the data plate & was suspicious when I couldn't find stamped #'s. I'll be contacting your "old" friend.

Titus- thanks for the input- hyd. control valve is new- just replaced. No oil leakage out of return line when mast is drifting.