47RH transmission Questions

[bvanetten]

I'm currently controlling OD and lockup via toggle switches. I don't have the dodge computer (or any other computer) installed on the motor or the burb and I need to know the theory of operation for the 47RH transmission to help design a controller. Fluid temp, line pressure, rpm, mph, kickdown cable? Are these the systems that the dodge controller logic uses for L/U and OD? I'm really more concerned with what values are used to determine when OD and L/U are turned off. I've already forgot to turn off the TC while stopping (bad noises and vibrations come from the transmission area!) and if you leave OD on it shifts from 2nd to third and then to fourth immediately.

Thanks
Bruce

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1972 Chevy Suburban with 1990 D350 4x4 CTD Chassis, 618a transmission, 12cm housing, tweaked pump, 3 1/2" straight pipe, autometer gauges

 

[Joe G.]

Bruce,

One thing you might do to make operating the TCC switch easier is to put a floor button in series with the switch on the dash. Use a dome light switch so that when you step on it it will disconnect the ground. Then it's kind of like stepping on a clutch when you stop to temporarily unlock the TCC.

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Joe George
Eureka, CA

'95 2500 CC auto 4X4,3. 54,Combo EGT/boost guage,custom switch panel,PacBrake,TST #5,DTT TC/VB,Automatic motorhome steps on both sides,Foldacover hard bed cover,Cummins chrome kit,Black steel grill guard,Front hitch receiver, KDP 160,000-NM-WT Insurance

 

[Strick-9]

bvanetten,

I believe my next project will be a transmission controller also. I've been toying with this idea for a while. I've already made my own TC unlock device to save the lockup clutch under full power. The next step is to add overdrive control to the box.

To answer your questions. I couldn't possibley give a complete rundown on the logic involved, but I'll try to cover the basics. We'll start with lockup.

Since you don't have the PCM, we won't get into lockup in 3rd w/ OD off and lockup in only 4th with OD on.

The convertor is setup to lockup in it's highest gear, and to NEVER be locked up during a shift. You can lockup in 3rd as long as you unlock during the 3-4 shift.

The convertor should be unlocked when the throttle is at idle or more than about 75-80% WOT. You need a potentiometer on the throttle (aka TPS) and a comparator circuit. While cruising, if you let off the throttle, the convertor unlocks, but it doesn't lock immediately when you reapply throttle. There is a slight delay of about 3-4 seconds. A simple 555 timer circuit could take care of this. This will help overall driveability.

You'll also need a speed signal. Your speed sensor is a frequency sender. You'll need a frequency to voltage convertor for shift points.

I want my 3-4 shift point to occur at 55-60mph and my 4-3 downshift to occur at 45 mph. This will allow enough hysteresis to avoid constant "hunting" when driving near the shift point.

Your value may differ depending on governed speeds and personal choice.

I have no idea how you could implement throttle applied downshifting, or variable shift points with a simple controller. That is, unless you are VERY good with electronics and microcontrollers.

The device I'm building, isn't too hard and I am not an electrical engineer by any means. The only part I haven't worked out is the frequency to voltage conversion.

-Chris

'94 2500 4x4 auto w/ DTT TC/VB, TC saver, Diamond B 370's, delivery valves, governor spring kit, AFC spring kit, extensive fueling mods, jardine 4" exhaust, propane.