Need to connect your GPS system to your tractor hydraulics. How about your laser system. I have several black box interface units that will take a bang-bang or proportional laser or GPS grade signal and run your tractor hydraulics by plugging into the armrest or electronic valves. Available for: John Deere 7000, 8000, 9000. New John Deere interface for 7R, 8R/8RT, 9R/9RT tractors for $895. Cat A,B Cat C, D + Case Steiger older style armrest Case Steiger Tier 4 Prices range from $895 to $1195.