A follow up to this: The problem definitely disappeared! I also changed the return to dig switch AT184726 ($180). I think it may have been chattering and making things worse. It turns out that I am pretty sure it is a CPI E1117 limit switch, which is a bit cheaper. You'll just have to add the weatherpak connector. All the best, WC- P.S> CPI also seems to make the diff lock switch which also costs an arm and a leg (could be PN J4001 to be verified)