sure thing. As far as how to 'control' the overdrive, I've copied/pasted a few paragraphs (and main link) below from a write up I have also in the diesel section, "Decomputerize your Dodge" -
https://ramchargercentral.com/diesel-talk/'de-computerize-your-dodge'/Personally I like a simply toggle switch to control the overdrive (and lockup if so equipped) - I like shifting the OD 'manually' via a toggle switch, but B&M makes a controller that will do it too (described below), the application of which continues to work perfectly in Homer's RC "Levi" for many years now. Lemme know if you have any questions.
Here's the verbiage -
"When it comes to electronics and controls for the entire transmission, the diesel A-518 had three electrical plugs: the 3-pin neutral safety switch, the speedometer electro-mechanical sending unit (2wd was electronic, 4wd was mechanical from the NP205 transfer case that was converted to electronic), and a very basic 2-pin plug, just behind the gear selector/kickdown levers. This 2-pin plug is the one we will focus on. The rear pin is 12v source power, and the front is the ground, which when grounded/ungrounded activates/deactivates the overdrive. The factory PCM controlled that functionality. We do it manually via a very simple 12v toggle switch or button ‘on the dash’. In other words, you can control the overdrive at the touch of your finger. We actually found a fantastic location for the overdrive button using the factory 2nd Gen (98-2001) column shifter lever. At the tip of which is where the factory put the on-off button for locking out the overdrive. We simply remove that button and install one very similar from Del City that is a very basic on-off button; #73556 from
www.delcity.com. This is what we use to control the ground circuit for the overdrive.
In 1994, Mopar introduced the diesel A-618, a.k.a. the 47RH. It was literally the same thing as the A-518 but with two main differences: It had stronger guts, and it had a LU converter. The diesel 47RH was only around for two years, when in 1996 the 47RE was introduced. The 47RE was available up to 2003, when the 48RE was introduced. The major difference between the 47RH and 47RE, is the functionality of the OD and LU converter. The 47RH and 47RE each have three similar electrical connectors on them, similar also to the 46RH, and it is important to be able to visually determine which is which when you are shopping for a transmission for your truck. Each has the same old-school 3-pin neutral safety switch on the drivers side, just above the pan. Each has a speedometer signal unit in the tailhousing. And each has either a 3-pin inline or 8-pin round plug just behind the shifter/kickdown lever assembly. This 3-pin/8-pin plug is what distinguishes a 47RH (3-pin) from a 47RE (8-pin). Many, many people selling a transmission think their 47RE is a 47RH because (when asked) they think the 3-pin neutral safety switch ‘is’ the OD/LU switch. It is a very common mistake, and can be an infuriating problem for buyers. Get pics before you buy a transmission.
The 47RH is essentially also just a 727 with an overdrive bolted onto the back. The valve body/1-2-3 shifting etc are all controlled by a hydraulic governor assembly located within the tailhousing unit behind the overdrive. The RH overdrive and converter lockup are controlled via the 3-pin connector. The center pin is 12v and the two outer pins are ground (front is OD, back is LU). The OD and LU are typically controlled via the PCM – taking drivers inputs, heat, all sorts of signal inputs etc, and eventually grounding the two outer pins when the PCM says so. Well,…that can be done manually via two little toggle switches on the dash. Meaning, you can eliminate every single sensor and the PCM, and have a toggle switch (or any other switch of your choice), and manually control the overdrive and lockup to engage and disengage exactly when you want. If you never hook up switches to the OD and LU the transmission will still shift through 1-2-3 just like any other 727. But, the 47RE does not operate that way – it requires the factory PCM for it to operate normally because it has an electronic governor. This is the main reason why most people doing a diesel conversion prefer the 46RH (A-518) and 47RH (A-618) over the 47RE (A-618).
To control the OD and LU simply requires two little toggle switches somewhere within easy reach of the driver. When you want the overdrive to engage, hit the switch. When you want to engage the lock-up, hit the other switch. It’s primitive, yes, but very easy and 100% effective. Just don’t forget to turn them off when you start slowing down for a red light, especially the LU. If you don’t disengage it, it could stall the engine.
Now, what about an ‘automatic’ way to control the OD and LU? That…is one of the items at the top of our list, and we think we have a way to do it, using off-the-shelf hardware from B&M. We are still verifying it will work, but the theory is sound. B&M produces a ‘Torque Converter Lock-up Controller’ #70244 and 70248 for a Chevy application, which simply sends a 12v signal to the trans at a pre-determined speed. The signal comes from the transmission speedometer signal generator, and at a certain speed the controller sends 12v signal to the transmission which activates, in this case, the LU.
The difference between the Chevy application and the Dodge application, is that Chevy's are factory engineered to use 12v signal to activate their OD and LU, whereas a Dodge is factory engineered to use a ground signal to activate their OD and LU. It's essentially the same difference. We are convinced, however, that the Dodge 2 and 3-pin plugs can very simply be 'reverse-wired', so that instead of the center pin going to 12v power, the center pin can be set to ground, and then the two outer pins for OD and LU can be triggered via input 12v signal, which is exactly how the B&M controller is designed to operate. The question of whether or not the Dodge solenoids can be reverse-wired seems sound, because all they are are electromagnets which close when triggered, and it should not make any difference whether or not the pins are reversed - the same effect should happen. We have yet to do this mod and therefore cannot say it works for 100% certain, but the math adds up."
(Edit: confirmed - they can be reverse-wired)
