Hi, I recently swapped a 47rh transmission into my '93 Dodge 1 ton, behind the Cummins. So now I have a lockup torque converter. I am operating it with a toggle switch on the dash. I thought that would be no problem but I ran into a situation where it was. Somebody pulled out on me when I was doing about 60 MPH and I had to do a panic stop. Jamming the brakes, steering the truck, just paying attention to what was going on, I didn't hit the switch to unlock the converter and it pulled the motor way down. It was like driving a manual transmission truck and not stepping on the clutch.
I have heard that there is a way to wire a pressure switch in series with the toggle switch so that the torque converter will unlock at a certain mile per hour.
Can anyone clue me in on what switch to get, and where to screw it into the transmission? Thanks, Joel
It takes some work and I don't have the info on hand anymore but I used two adjustable Hobbs switches, one low pressure and one high pressure, two different part numbers because the adjustment range isn't that great. The low pressure is for unlock and the high pressure is for lock. If you don't have two switches the O/D will hunt at the set point, really annoying. I wired them with two relays so the low pressure switch closes but the ground goes through the high pressure relay so it doesn't engage until the high pressure switch is closed. The low pressure switch relay latches the high pressure switch relay closed until the low pressure switch opens and releases the relay. I ran the whole mess through the O/D driver in the PCM through another relay so as not to burn the PCM driver out and L/U only works in O/D. There is no way to separate it in the PCM. Mine works like factory, locks up at about 47 and unlocks at about 42. It will even kickdown.
The port you need is at the back of the main case on the right side, opposite the rear cooler line.
The switches in the stumped ones link didn't work for me as the governor pressures on the diesel are much higher. Gas models are typically 1 psi per MPH but mine had 60 psi at 30 or so MPH and over 90 at 60. You will need a pressure gauge to check what your governor pressures are at the speeds you want to lock and unlock, then order your switches based on that.
If I come across the wiring schematic I'll post it, but lord knows where it is now.
