It would be great if you could change the shift points for your application. I plan on using an electronically driven speedometer anyway, so I would want to have the electronic signal setup that this transmission has anyway.

Hoozie, what is required to have a customizable shift points? I mean, would it be the final gear ratio as well as the circumference of the rear tire to control any adjustability to the shift points? Is there any other ways to control the shift points? I plan on using this controller with a Gen II 426 hemi architecture, and I want a 3.33 rear gear ratio with a weird rear tire circumference as well.

It would be good if shift points as well as LU and OD were customizable, because the guy doing this modification probably isn't going to be doing much stock stuff anyways............

Thanks,

Mark

If the controller had a built in MAP sensor you coudl use that to determin load. Similar to the MegaSquirt controllers.

The factory used cold temp tables to keep people from abusing the transmission, you should be able to omit that with a warning to the user that he/she should let it warm up before getting on it.

It would be very nice to have a tow-haul mode (or 4-LO) that'd use an alternate table to keep the RPMs up longer.

-Ben

So I've been thinking some more about how to control the shift points. It's a bit tricky, since it isn't like other transmissions that have solenoids I can control to select a gear.

The RH governor outputs roughly 1psi/mph. The governor pressure is the only thing I can control on the RE.

Basically, the governor pressure and throttle valve pressure push on opposite sides of each shift shuttle valve. Once the governor pressure is higher than the throttle valve pressure, it shifts (I think). At low throttle positions, the governor pressure wins sooner, and causes an upshift. At higher throttle positions, it takes the governor longer to overcome the throttle valve pressure causing higher shifts.


So help me out here: Since the governor pressure has to be higher than the throttle valve pressure to cause an upshift, to raise the shift points, we want the governor pressure to be lower than it normally would be? Right? If we want really low shift points, we'd want higher governor pressure?


I'll likely have to include both a MAP and TPS (throttle position) sensor inputs.

Also, since OD & LU are solenoids I can control at any time, I can use a simple mph on/off, or even a curve based on load.

Is there anyone in the southern Oregon area with a stock RE I can do some datalogging on?

Find yourself a 1993-1/2 or later grand cherokee with the straight 6. It had the first RE trans in it. The V8 GC had the RH trans. These RE's had a standalone control module to run the trans. It took inputs from the engine controller for TPS, temp, etc. The TCM "makes" the gov psi by using a PWM solenoid and reads the gov psi by using a pressure transducer. These early units had a thermistor on the harness in the pan, later we went to a pressure transducer having a built in thermistor. The shift schedule is mapped. 1-2, and 2-3 are all controlled by this map using gov psi and it's fight against throttle pressure. You don't control shift quality using gov psi or throttle pressure. You get hard shifts because of high clutch capacity versus anticipated engine torque. That's why sticking the throttle lever back and then driving around town gives you harsh shifts, low torque going in to the trans in anticipation of high power levels coming in and not being realized. The 3-4 shift is all done with electonics - we spike gov pressure to force all the 3-4 valves over then hit the OD solenoid then the LU solenoid. There are lots more controls than this - this is a summary.

Actually... my dad has a ~96ish GC, straight 6 with an automatic. I bet it probably has an RE in it. Now I just need to see if I can borrow it for a while

So Transman, if the early GCs already have their own controller, what's keeping us from adapting that to standalone use? Or, is the connection to the PCM mandatory?


ahh, it looks like we lost a couple replies with the software change. iirc, it was confirmed that to raise the shift points, the governor pressure has to be lower than baseline.

We went away from the standalone trans controller for 1996. 1996 was the first year for the integrated engine and trans controller on the RE family for all engines using the 42/44/46/47RE. Only the 4.0L had this standalone controller before 1996. You can change the shift schedule electronically through the software map or by changing the governor weights or by changing the shaft speed "read". To raise the shift point you would need to lighten up the primary (outer) governor weight. Trial and error but nothing that difficult. As for adapting this controller you need to determine the feeds to it and what form the signals are in. I would start with the Service Manual.

I checked and found no info of a RE trans being used prior to 1996. The Cherokee used either a 32RH aka 904, or a AW4 which was a Japanese unit.

I think if you search under 4.0 Grand Cherokee, you will find the 42RE was used from 93 to 98.

Kevin

Just to give this a boost, I will be in the market for this exact unit.

I want to put a complete 98 Ram 5.9L/46RE drivetrain in a '68 Charger shell. I can grab the ABS controller so it will relay the data to the PCM, but I need a signal generated at the correct frequency to simulate the rear axle sensor.

It would be nice to be able to ditch that for a stand-alone unit.

bump from the dead ,any news ?

ats have a pricey stanalone for the diesel crowd ..

ats controller

My main hang up was wrapping my head around how to design the mapping table, but I may have just figured it out:

So baseline is 1 psi governor pressure per 1 mph (60mph = 60psi).

At higher loads, we want a lower governor pressure to raise the shift points, so something like 0.8 psi/1mph (60mph = 48psi). At even higher loads, we may want even lower governor pressure, so 0.6psi/1mph. So if you floor it from a stop, the governor pressure will rise slower than if you drove off normally, and with the pressure being lower the shift points will be higher.

So, a chart with a multiplier as the y-axis, and Load (MAP or TPS) as the x-axis.

The y-axis is centered around 1, with the curve able to go to lower (or higher) multipliers at higher load values.

So, I look up the current multiplier for the current load, and multiply that by the current speed to get a target governor pressure. Then I command the governor solenoid with feedback to reach that target pressure.

At lower loads the multiplier can be adjusted up or down (greater than 1, or lower than 1) to get the desired shift points.

Questions:
1. How is downshifting from 3->2, or 2->1 done internally when under load? Does it happen at all? If you're puttering up a hill in 3rd, then floor it, does it downshift to 2nd, or to 1st?

2. Should I have the option of forcing the governor pressure high to force an upshift at a certain (high) RPM?

3. Since lower governor pressure leads to higher shift points, what would happen if I commanded zero (or very low) governor pressure throughout the MPH range?

You wouldn't want to downshift to first with a load going up a hill.

Is this lockup or no lockup ?

I'm assuming in that case that OD/LU would both be off. I guess I'm wondering what a 727 would do in that situation.

Or am I thinking about it too much?


Does the rest of my theory of operation appear to be sound?

The thing about a 727 is that it doesn't shift down to 2nd when slowing to a stop, it drops directly from 3rd to 1st so it'll stay in 3rd at a pretty low road speed. If the road speed is low enough in 3rd when the throttle is floored it'll kick down all the way to 1st and I assume the RH will do the same thing...never tried it with an RE but I think it'll do the same thing.

Just spitballing but I believe an RE standalone controller would need a TPS, a TP cable and a speed sensor...the logic to make them all work together is way over my head.

Yea, thinking more about my 727, there have been times I had to manually shift into 2nd when the RPMs dropped too much.

In an RE, what happens when the shifter is placed in 1st or 2nd? Does it no longer matter what the governor pressure does?


The throttle pressure (kickdown) linkage would still be required, but would be completely external to the controller.

I would also need at a minimum a road speed input, and either (electronic) throttle position or MAP (engine vacuum/boost).

I think I outlined the logic in my previous post. Basically, at higher engine loads/throttle positions, I can command a lower governor pressure to induce higher shift points. And make that curve adjustable by the end user to tailor to their preferences.

I'd be happy if you could just build a full manual controller.

Kevin

So, it looks like this is actually happening. Schematic is probably 1/3rd done.

Looks like it will have:
Inputs:
VR speed sensor input (two wire)
12v PWM speed input (hall-effect sensor)
TPS
MAP
RPM?
4-LO
Overdrive disable button (any reason to have a lockup disable button?)
Stuff from the transmission


Outputs:
12v PWM speed output (to drive speedometer?)
status LEDs
header to transmission (obviously)

Other:
USB (will have a software program to set up parameters)


Is there anything I'm missing? Anything that would be nice to have?

I will also need a guinea pig someone with a running RE transmission to help me test everything.

so I know I have efi to piggy back off of, but for those that run carb still, can you power these extra sensors? are there adapters for carbs for the tps?

oh, and do you have enough transfer/program if you used micro usb?
perhaps an android app instead of full laptop?

Yea, there are cable adapters that hook to a carb to provide an electronic TPS.

For carb people, I was thinking that the MAP would be enough to determine engine load. The MAP sensor will be inside the box, so you'd have to run a vacuum line to it.

Was planning on a uUSB header on the box. Hadn't thought about an Android app