How to control 47Rh lock up with a pressure switch?

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

Might be some good info here. https://transmissioncenter.net/shop...ere-for-727-to-46rh-swap-wiring-diagram/

PATC and E Trans Control

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.

Well it's not on my PC, I didn't think it was, so it's on paper somewhere.
Alternatively you could splice your lockup toggle switch ground into the O/D ground wire to the PCM. That way when the trans comes out of O/D it will unlock the converter as well. I would run it through a relay though just to be sure you don't burn the driver out in the PCM. Blue wire is ignition hot, orange with tracer (blue or white, I forget which and I'm color blind so keep that in mind ) is the ground.
Edit; the O/D kicks out at about 30 mph which is too low for the L/U clutch to be on, but it would at least unlock it before the trans downshifts into 1st.

Here's what I did for my 46RH



518 Control

Completely automatic, wanted my daughter to be able to drive it.

The control module automatically turns on/off the overdrive and lock-up for the transmission.

The 518 (46RH) is hydraulically controlled and uses 2 servos to enable the OD and LU.
The 3-pin connector on the transmission supplies the control voltages.
The center pin always has 12V power connected. The 2 outer pins are switched grounds. The front pin is the OD ground, the rear pin is the LU ground.

The module works according to the following sequence.
1) The 12V toggle switch supplies voltage to the relays and transmission center pin.
2) When the hydraulic pressure trips (50mph/adjustable) the pressure switch, ground is supplied to the vacuum switch. When speed is below 50mph, hydraulic switch opens, disabling OD.
3) When there is enough vacuum, the vacuum switch closes, providing the OD relay ground. Under heavy acceleration, vacuum drops, opens switch, OD is disabled.
4) When OD relay has ground and 12V, it waits 10sec, then supplies 12V to the LU relay and ground to the transmission OD pin, enabling OD.
5) Now the LU relay has 12V, it's already grounded. It waits the 10 sec programmable delay then provides ground to the transmission LU pin. So lock up doesn't occur until OD has been enabled and on for 10sec.
6) The programmable delays for both relays fix the situation when speed is fluctuating around 50mph. This would normally cause the OD to kick on/off, the 10 sec (programmable) delay stops this from happening.

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 switch

I 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.

Thanks for all the great information. I am not really needing full automatic control, I have been operating the overdrive with a toggle switch for years. In the occasional instances when I forget to switch off the overdrive, I have come to a complete stop, then got the truck rolling again with it overdrive. Then I notice it and hit the switch, but no real problem. Not so with the lock up. So I really need just a safety to disengage it if I forget, or in a panic stop. I think one of those adjustible pressure switches would do the trick.

https://www.manciniracing.com/acoloco.html

Have you looked into the compushift controller? Not cheap but another option.

Depending on how and where you drive just install a switch on the injection pump throttle lever.

Fully closed it opens the L/U circuit. Or something off the brake pedal.

If you would have checked out the patc link they also have one for diesels.
https://transmissioncenter.net/shop...omputer-made-for-diesels-without-vacuum/

Look for Hobbs Switches. W.W. Grainger used to have a bunch of different ones to choose from.

some older car & trucks have a dual brake light switch, one opens when the brakes are pushed & unlocks the converter, the other turns on the brake lights

Most of those old dual brake switches actually interrupted the cruise control and turned on the brake lights.

On all of the Chrysler vehicles in the 80’s up to the 90’s used the brake switch as an input, along with the N/S switch, VSS, TPS, battery (ambient temp) temp, coolant, trans temp, and some others. Depending on the algorithm, it controlled L/U, O/D.

that's what i was going to say. it unlatches the cruise unit, but i forget if it goes through the control on the turn signal stalk, or the unit itself under the hood.
would be a super easy thing to wire up.

I would like the torque converter to stay locked up while I am using the exhaust brake, but still drop it out of overdrive if I choose to.
If I use the brake light switch, and I want to use the brakes and the exhaust brake simultaneously, that would unlock the converter and reduce the effectiveness of the exhaust brake. So that pressure switch would probably be the way to go. Once I get the truck down to 40 miles an hour or so, the exhaust brake probably isn't needed.
This truck is always very heavily loaded, with a big camper in the bed and/or my race trailer behind. So I actually prefer a mostly manual control so I can use my senses and my brain too make decisions rather than rely on an inflexible automatic device.

Yep I understand that, but I am going to add a brake switch on my Charger, but I dont have a Jake Brake

Great! I guess I don't have to feel bad for not finding the schematic then.

If you are using a stock 47 and hauling all the weight using a Jake - you should consider some of the devices out there’s to crank throttle pressure/line pressure up.

Closed throttle will drop line to 60 +/- and using the Jake with a lot of weight can take it’s toll on the clutch’s.

Transman, the transmission is built, but I don't know all the specs. I'll ask the guy who built it about that. I known it has hd clutches, kevlar bands, more oil to the overdrive, valve body mods, etc.

I went ahead and ordered the 20 to 120 psi switch from summit.
Maybe I should connect that to the 12 volt input wire, and then keep my two switches hooked up to the ground wires. Then get the switch adjusted so that it powers up both the overdrive and lock up at about 40 to 45 mph. Then keep my switches off and until I am ready to activate them. At least that would drop them out if I have to make a quick stop, or if I forget to. Thanks for all the help!

Transman, I talked the guy who built the trans today. He said the pressure has been increased, but he didn't know offhand how much. What do think would be a minimum pressure during deceleration using the exhaust brake? He mentioned putting a solenoid that somehow operated the cable to increase pressure when using the exhaust brake. That must be the devise you speak of. Where would I hook up a pressure gauge to test it? Thanks, Joel

Use the line pressure tap to monitor, passenger side of main case, center tap.

By increasing pressure I assume he means line pressure by adjusting the Allen head screw on the valve body.
But that won’t help you at closed throttle on the Jake hauling all that weight.

He is correct, adding a solenoid or driver motor to move the throttle pressure cable lever all the way back when using the Jake is the direction you want to take.

The later 48RE transmissions have a TTVA on them to accomplish this very thing for the same reason.

Also the Jake is much more effective when the lockup converter is on.

Thanks for that info. Does anyone have a link to a device like we were talking about to kick up the pressure when the brake is activated?

I also loved driving my 47RH-equipped 1st gens with OD and LU on toggles - puts me in charge of them. So what you're looking for is something speed-related that will 'enable' the LU circuit over a certain speed, like 15 mph or so, and disable (unlock) it below, correct? I don't know if this would work, but if you have a 4x4 (NP205) I think you can thread one of the slick B&M Converter Controllers (i.e 70244 - link below) onto the t-case speedo output and wire it to a relay, which could 'enable' your manual LU toggle at whatever speed you'd want. The controller simply outs 12v signal at speed 'X' - B&M markets the thing to control LU on a GM but it could be used to turn on 'anything'. You can dial in whatever speed you want. Buddy of mine uses two of them in-line with the mechanical speedo in his 87 Ramcharger to control both the OD and LU - all automagic, and all adjustable. Not sure it'll work for your 93, but if so then coolieo.

There's a couple different versions of the thing - the 70244 is for mechanical speedos and the other for electric - maybe you can make one of them work? I have an Atlas t-case in my 02 big block Dakota with a mechanical speedo and the I'm considering using one to disable LU in my 46rh.

https://www.summitracing.com/parts/bmm-70244

- Sam

https://www.xtremediesel.com/bd-power-pressureloc-transmission-kit

This was the one I saw “back in the day”….. but no longer made