Hey All,

 

I would like to find a simple, inexpensive and automated way to adjust when torque converter lockup occurs. I am not interested in off the shelf transmission controllers. I have an electronics and industrial automation background. I am interested in hearing ideas that pertain to a DIY install and long term reliability, as well as ease of use for someone else driving the truck.

 

I have 3.54 gears and 35" tires. I'm fully aware what that means for my final drive ratio, and I'm not entertaining a regear at this time. Please don't suggest obvious large mechanical changes.

 

The truck has a lockup switch, which I generally don't use. While cruising at around 60km/h, in 3rd gear, my TPS is hovering right around the area where lockup is allowed (12% ish). There is only maybe a 2% hysteresis here, and the converter will unlock (thanks Chrysler). This is especially obvious if I set the cruise. Lock, unlock, lock, unlock. Couple this with the fact that my RPM's are too low in this situation, and a little bit of surging can occur. Really, if this trans was properly controlled, it'd be in 2nd lockup at this point. But let's not dive into that. 2nd gear might as well not even exist in this heap.

 

A similar but less severe situation occurs at 85-95 km/h in Overdrive. I'm not as concerned about that, I usually lock out O/D until at least over 100 km/h. I mostly want to clean up 3rd gear mid speed cruising.

 

So ideas. I could adjust the Quadzilla's 0-5 psi fuel percentages. If I decrease these percentages, it will force more TPS % to go the same speed. This only fixes half the problem; it'll still lockup too early, just won't keep unlocking because of low TPS. And there's the obvious side effect of increased spoolup time because of less fuel.

 

I could tap into the TPS analog signal, and use a potentiometer to make an adjustable voltage divider to trigger a low voltage relay, and use the contacts of the relay to open up the lockup circuit until the TPS % is higher. This would be the ideal situation where possible. It would force lockup to be delayed until higher throttle, which would mean higher speed and higher RPM. Except, this may still allow the lock-unlock-lock-unlock situation, just moved into a higher TPS range. It might even make it worse. I could maybe use another relay to allow unlock at a different TPS but that's getting a bit complex.

 

If there was a DC wheel speed signal somewhere, I could do something similar with a speed trigger instead. But I'm guessing all tappable speed signals are AC (or rather pulsed DC).

 

I'm sure there are more reasonable inexpensive solutions that I am not aware of. I'm going to keep thinking about this, and I plan on implementing something when the snow is off the ground.

 

Thanks in advance for your ideas.

 

On ‎3‎/‎16‎/‎2018 at 8:19 AM, Dynamic said:

It is my understanding that Chrysler received the engine assemblies from Cummins complete with electronics (APPS, ECM, etc.), and ready to drop in as a pre-configured unit. The ECM simply outputs a 0-5V TPS signal (based off of the APPS signal the ECM sees) and crank sensor signal (to reference engine RPM) to the PCM for use in controlling the transmission

 

On ‎3‎/‎16‎/‎2018 at 8:19 AM, Dynamic said:

 

There are a myriad of different - let's call them "anomalies"...to be polite - that I would find "work-arounds" to if I was a smarter guy. This is definitely one of them. I have, on one truck that I built a transmission for, played around with some fixed resistors on the TPS signal line to delay the shift into OD, which did work, but that truck was a 12 valve with a 47RH, so I was just manipulating OD and TCC lockup. I would surmise that the same could be accomplished on a 47RE with some ingenuity

On ‎3‎/‎14‎/‎2018 at 8:15 PM, kzimmer said:

Below is a screenshot of the factory service manual. Not shown in this screenshot is the APPS, which is wired to the ECM. It looks like, for some reason, the APPS (TPS) signal is repeated by the ECM and retransmitted, hard wired, to the PCM. I have no idea why they chose to do it this way instead of sending it over the data bus. I also don't know how it's scaled. Assuming 0-5 VDC, just like the ECM. Can anyone verify? I'll measure if need be.

 

 

I did this to" fix" some "anomalies" that my truck experienced at specific apps - throttle positions relating to shift points and lock up points about 15 years ago , fixed them

As I understand the ecm may be changing the apps signal just enough for the pcm to cause the problem  , tying the apps to the pcm before the ecm is a purer signal

 

Also wondering if maybe if you haven't recalibrated your speed  tire size ,maybe that could cause shift - lockup issues   

4th Gear Hunt Fix (1998-2002) v1.0 (1).pdf

Edited March 6, 20196 yr by dieseled
misspelling

This was almost a year ago. I broke the truck shortly after this post was started and haven't fixed it yet. Haven't done any work with the lockup. Very interesting article though, I haven't seen that one around, thank you for the info.

 

As someone that works in the electrical controls industry, it is not standard practice to run one analog device to two separate analog inputs on two separate measurement devices. Will it work? Probably. Is it a good idea? Likely not. I think there is probably a reason the ECM repeats the signal to the PCM, instead of paralleling the two inputs to the one sensor.

 

I was able to watch the throttle position % on IQuad and recreate the problem every time. I'm confident a dirty signal didn't cause my problems. 3.54 gears, 35" tires, and a non adjustable PCM caused my problems. Fixing any one of those 3 things would help my situation. I'd prefer #3 but as far as I know it's impossible.

 

My truck is also calibrated for tire size. I could move the lockup and 4TH gear shift if I lied to the truck about tire size. But then my speedo would be off.

To add:

I just saw the part where they say to tie the apps signal return wire to ground. Ugh! No! Wtf ATS?