The GST transmission on my L39 suddenly started to auto-shift; that is, when placed in most any gear it suddenly decides to rapidly bounce around to plus or minus the selected gear, displaying the gear changes on the display panel and confusing the drivetrain (and the driver). Is there an intelligent path for troubleshooting this problem or knowing guesses as to the obvious cause? The tractor has just over 800 hours and the transmission fluid and filters were replaced roughly 30 hours ago. All other hydraulics work just fine. Previously, 1st and second gear would occasionally disappear but 3rd seemed to have become 1st, but the cause (hot or cold, forward or reverse, 2WD or 4WD) was not consistent and I simply worked around the annoyance. This escalation of what I assume to be part of the same problem is a little harder to ignore.