computer-controlled transmissions (4l60e)

[Storm Chaser]

I have a question for the ecm guru's out there...

I know that the 4l60e and 4l80e transmissions are electronic, but is the electronic data going one way (to the transmission) or is there signals going the other way too?

In other words, say you have a 1994 or 95 (with the ecm still under the dash). If all the wires to the plug on the tranny were only carrying signals one way, TO the tranny, then the ECM wouldn't know the difference if you unplugged the tranny, right? It would still send it's signal down the wires, plugged in or not, but it wouldn't affect the running of the engine.

However, if there is anything at all being sent FROM the tranny back TO the ECM, then unplugging the tranny might present a problem.

The reason I am asking, is I've been searching this on the web for two hours now- if you have a truck with a 4l60e, and you yank it out and put in a manual, a th350/400, a 700r4, etc... DOES THE ECM KNOW, AND DOES IT HINDER THE OPERATION OF THE ENGINE OR OTHER ECM FUNCTIONS??

Of course, I'm only talking about the round plug to the tranny. For the purpose of the question, lets assume that converter lockup and VSS is dealt with and operating properly as needed.

[ChevyTech]

The transmission does have sensors, and information goes back to the PCM/computer.

If the transmission were swapped to a non-electronic controlled transmission, trouble codes would be set in the computer. I don’t know just how many drivability problems would occur.

[Storm Chaser]

Thanks for the answer. I'm looking at the crude wiring diagram in the Haynes manual... the only sensor per se that they show in the transmission is the tranny temp sensor. Along with that is the 1-2 shift solenoid, the 2-3 shift solenoid, the 3-2 shift solenoid (for 4l60e), the TCC solenoid, and the pressure control solenoid. There is also a range mode selector.

If I understand this correctly, the signal flow to all the solenoids comes from the PCM- it either opens the solenoids or it closes it (depending on if power is present in the wire to the solenoid). It would seem to me that the PCM wouldn't know if the solenoid is actually there or not. However, the temp sensor is sending a signal TO the PCM, so assuming I have this right, there is where the trouble would be with the tranny not hooked up... and maybe the range control....

Which is my next question- what is the range mode selector? I'm guessing it is sending a signal back to the PCM telling it what position the gear selector is in. Am I right?

And another related PCM question- there are three inputs to the PCM- 4wd input, cruise input, and AC input. From what I can find, the AC input raises the idle speed if the air is on. I know a signal is sent through these inputs when the corresponding system is activated, but what does the PCM do when the cruise or 4wd is on?

[ChevyTech]

Originally Posted by Storm Chaser

If I understand this correctly, the signal flow to all the solenoids comes from the PCM- it either opens the solenoids or it closes it (depending on if power is present in the wire to the solenoid). It would seem to me that the PCM wouldn't know if the solenoid is actually there or not.

The PCM monitors the voltage on these wires as well as applying power to the wires. When power is applied to the solenoids (with the wiring connected) the voltage is somewhat lower on the circuit then it would be if the wiring were not connected. If the voltage does not read within an expected voltage range the PCM will detect this.

Which is my next question- what is the range mode selector? I'm guessing it is sending a signal back to the PCM telling it what position the gear selector is in. Am I right?

Yes

And another related PCM question- there are three inputs to the PCM- 4wd input, cruise input, and AC input. From what I can find, the AC input raises the idle speed if the air is on. I know a signal is sent through these inputs when the corresponding system is activated, but what does the PCM do when the cruise or 4wd is on?

The cruise input may be used by the PCM for engine breaking under a steep down hill condition, but I don’t know for sure. As far as the 4WD I think the PCM only gets a signal for 4WD Low range, and I don’t know what it uses it for.

[Storm Chaser]

Thanks for all the info. I figured I was taking the easy way out using a 95 harness and PCM on my crew project (95 has the new dash, but the old engine controls). However, after I bought everything, I found out that the 95 4l60e is a one-year transmission, which I still don't understand what the difference is. I was just trying to feel out a way around the problem, but I'll have to think of something else I guess.

[OJOE]

Originally Posted by Storm Chaser

Thanks for all the info. I figured I was taking the easy way out using a 95 harness and PCM on my crew project (95 has the new dash, but the old engine controls). However, after I bought everything, I found out that the 95 4l60e is a one-year transmission, which I still don't understand what the difference is. I was just trying to feel out a way around the problem, but I'll have to think of something else I guess.

you can send your pcm to someone like speartech and have them take out the auto trans stuff and set it up for a standard shift