Automotive → Re: GM 4T60-E Transmission

You will be missing far too many data inputs to make Pulse-Width Modulation a reality by just using the shift pattern. It is far more than just a program or routine. It needs to know throttle position, manifold absolute pressure, barometric pressure, coolant temperature, fuel flow rate, airflow rate, transmission gear position and ambient temperature just to name the few I can think of off the top of my head.

Sounds interesting...but VERY complex!

true.
even if you were to do this manually (without any input from any sensor, even with a computer module) you would have to know when to downshift at certain speeds such as going uphill, when to upshift and when to release back to the appropriate gear depending on the speed.
most of the data taken for gear shifting is done by the speed sensor and TPS sensor, and on some vehicles, the engine rpm.
so while my test did work, it was the biggest pain in the ass to drive that way, lol.

I might add, the driver would have to maintain the same pattern to make it work...in other words, slow and steady.

Yes, if you wanted the driver to drive it like people normally do, you would have to fall back to a computer making the decisions.

In analogous terms, I drive a 18 wheeler that has a gauge that shows engine boost pressure...I normally don't exceed 10 pounds of boost...but on hills, I go upto 25+ pounds of boost...hence, if your foot in "trained," it could be done, but you would have to stay within those parameters required, always, which most people would not.

Oh well, I thought there might be a simple back door...

None of the factory controllers care about ambient temperature, and those that use MAP only guesstimate barometric at startup and WOT. Coolant temp is minor, that's only used to prevent TCC lockup until the engine warmed up.

There's only 3 things that absolutely need to be known, load, throttle position and speed. Factory controllers do also look at other things, such as EGR.

You're way off on that one.

Nearly all newer GM products look at ambient during cold weather and when below a specific value (generally in the 40 degree range) they delay the normal shift sequence and provide a higher RPM shift point. This is done to provide a small reduction in engine coolant warm-up time, which has obvious benefits.

How do you suppose the factory controller determine load? It's a computation between MAP, TPS, and MPH. It's much more than a "guesstimate" at start-up...

And how do you propose they do that without a barometric sensor? GM did away with a baro sensor when they switched from differential sensors to MAP. Try reading a PCM hack, or better yet hack one yourself to really understand what it's doing.

And yes, some sensors are redundant. The PCM can calculate load from just one, if others have failed. And most are just fluff or added for OBD2 purposes, which is not to make the engine control any better. OBD2 was mandated by the EPA to monitor the emissions controls.

No,the PCM can not "calculate" load from just one input; it extrapolates it, which is a significant difference. It is not an accurate reading, it is an estimate to be used as a fall-back value in the case of a component failure.

Whether you want to believe it or not, the current crop of sensors with digital data capability has led to improvements in many facets of a modern automobile.

How is the "load" determined when all the sensors are working?

The 4L80E in my '96 K2500 pickup has a "torque sensor" in it. Is this related?

There is no "torque sensor" in a 4L80E. Did you see that notation somewhere? There is a torque converter clutch solenoid, similar to what we were discussing above. Nothing that senses torque in the trans itself though.

Sometime between when I read the diagrams for my 4L80E and now, I confused "force motor" with "torque sensor".

I think I'll go back to my nap now.

Ahh, OK. Force motor, aka "Pressure Control Solenoid". That's the modern-day electronic version of a throttle valve, or vacuum modulator. It responds by changing the valve body line pressure in correlation to throttle position and engine load.

Or, as one thing I read said, "based on the torque generated by the engine".

Primarily manifold pressure, throttle position and rpm. There's a few others that have a minor effect, such as coolant temp and A/C request.