450C steering clutch question

[Jack-the-Ripper]

My left clutch engages intermittently and does not pull well under load. The right one seems to work normally. I understand (or as near as I can tell from the manual) that, unlike the 450B whose steering clutches are held engaged by the pressure plate springs, the 450C has a hydraulic "throw in" piston (opposite of a throw out) bearing that uses oil from the transmission, to hold pressure against the clutch disks. It seems that this left clutch holds in some parts of its rotation, i.e., if the tractor moves a little, it will re-engage.

So I'm thinking either a) there is some constriction or other problem in the pressure system that is not holding in the clutch, or

b) there is some kind of irregular wear or pressure imbalance at the clutch pack, or

c) none of the above - something else I haven't thought of.

Any ideas on how to troubleshoot this before I disassemble the clutch pack? Anyone else had such a problem? I haven't found enough t-shooting info in the manual. Thanks,

Ralph