I've been trying to figure out why my 96' Ram won't shift into fourth gear and I've come to the conclusion that it's probably something electrical related.

There were no signs of a problem in the fluid when I dropped the pan. Mechanically the truck shifts fine thru all other gears. It does seem to hold 2nd gear too long at times when it should be shifting into 3rd to drop the RPM's though.

I think it may be the "O/D Off" switch or overdrive circuit, but the wiring scematic in the Chiltons manual only shows up to the switch itself, not to the tranny, so I can't exactly troubleshoot. Does anyone know where I can get a better diagram for free?

Thanks.

 

I don't know where to get a better diagram but the light bulb inside those switches go out very easily. I just replaced mine(the bulb) when I got the truck. The easy way to tell if the switch is bad is to get out on the highway going around 50ish or a little faster and push the OD button. You should feel the truck downshift to 3rd gear in a second or two. If it doesn't then likely you have a bad overdrive solenoid in the trans. When you first start the truck overdrive is on automatically unless you push the button on the dash to disable it.

 

I replaced the solenoid as well as the pressure sensor when I dropped the pan and nothing changed. I tried pushing the button on the highway and nothing happens - I've also counted the number of shifts. Maybe a factory shop manual will elaborate more, but they're expensive.

 

Take out the switch. Perhaps it is jammed and causing it not to be able to shift into OD. Either that or you have a wiring issue somewhere.