I have a 1978 ford f600 dump truck. it has the eaton 2 stage rear end. If i am setting still with the key on and i push the 2 stage rearend switch to down then it stops my frame mounted fuel pump from working. i can pull the switch back up to high and it starts working again. my father in law was messing with it and left it down too long and now it burned up my fuel pump. what could be the problem with this? thanks.

 

When I diagnosing electric problems there are 2 rules I go by first.
1. You can't have 2 many ground wires , Or a ground wire can't be too big.
2. I unhook, unplug or remove fuses feeding anything the vehicle wasn't build with day 1.
I hope this helps and good luck.

It sounds like bad connection. The wires for both will run down the frame from the front of the truck.
Maybe there is a connection between them whern there should not be.
Look to see if they are fed from the same circuit or wire.

 

I dont know how the wiring working on the 2 speed axle, but i would make sure the fuel pump has a good clean ground.

The only thing i can think that the two circuits should have in common is that they are hot with the key on...

 

I think I have checked all the wiring and dont find any place that they are linked together other than the keyed power. does anyone have a wiring diagram for the eaton 2 speed rearend. the only one I have found on the internet is the wrong one. it says there is a circuit board with a wiring harness on the rear end itself but mine dont have that. it only has 2 wires coming off the housing and a ground to the frame. thanks.