Diesels don't make vacuum, 50 psi of governor pressure is about 20 mph in a diesel and he already has O/D control in the pcm with a dash button to turn it off. I did find this adjustable fuel pressure switch at summit. Don't know how well it would hold up to ATF though.
Summit pressure switchI remember having a hard time finding correct pressure switches and ended up actually talking to a Honeywell rep on the phone to get the correct part numbers. I don't remember where I purchased them from.
