The electronic dash selector for my Allison MD3060 is not functioning properly. When I press D to drive the transmission does not engage. It will engage if I try it a few times / sometimes works the first time. My guess the problem lies in the dash switch itself. When I look behind the dash I find a large sealed unit with a model number of BP8 0005. Can this switch be user repaired or do I need to take it to my diesel shop?