When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
..and that's not totally correct, either, but Lead Head is much closer.
The EPC (Electronic Pressure Control) solenoid is not a PWM. It's a Variable Force Solenoid (VFS) that is current controlled by the PCM. The PCM maintains voltage, but varies the current to the solenoid to control pressure output.
The 5R110 and newer transmissions control each clutch individually with VFS solenoids connected directly to the clutch they control. This results in one solenoid per clutch, plus an overall line pressure solenoid and a converter clutch solenoid.
..and that's not totally correct, either, but Lead Head is much closer.
The EPC (Electronic Pressure Control) solenoid is not a PWM. It's a Variable Force Solenoid (VFS) that is current controlled by the PCM. The PCM maintains voltage, but varies the current to the solenoid to control pressure output.
The 5R110 and newer transmissions control each clutch individually with VFS solenoids connected directly to the clutch they control. This results in one solenoid per clutch, plus an overall line pressure solenoid and a converter clutch solenoid.
The solenoid itself doesn't operate in a PWM fashion (as in it doesn't rapidly pulse on/off), but the computer modulates the current going to the EPC solenoid using high frequency (relatively) PWM.
Well I figured out that apparently you can no longer buy a 1994 trs sensor. You get a 95 and the female plug is slightly differet than the 94. So you have to remove the 94 plug and replace with the 95. My wires going into the old plug had the insulation crumbling off them so I'll be using heat shrink to coat them. I guees I'll take my front drive shaft out to have more room to work unless that pigtail unhooks somewhere i dont know about. Thanks for all the helpful information guys! Jim
Pretty mich everything you just said is wrong. The E4OD is completely useless without the electronics hooked up. You will get 4th gear in drive, and 2nd gear in manual 1/2.
The MLPS does not power the solenoids in any way. It's only connected to the computer to tell the computer which range the shifter is in. The computer then controls the E4ODs 5 solenoids to manage shifting. Even in manual 1/2 the PCM is still managing line pressure and the shift solenoids, otherwise you'd be stuck in 2nd, as mentioned.
Line pressure is not based on resistance either. It's a PWM based variable duty cycle frequency control of the EPC valve.
The E4OD is about as electronically controlled as a 4 speed can get. The only thing modern 6 speed automatics do differently, is they typically have more shift solenoids since two solenoids only have 4 different states. Modern automatics typically have 4-6 shift solenoids.
I didn't say it didn't need electronics, I said it was simple. Modern automatics tend to have more inputs and often have a standalone controller on the trans that does some final logic. For example, shifter says X, ecu hears, X tells pcm Y, pcm looks at inputs from T, U and V, then does X, whereas the E4OD's inputs are all external, the wiring harness running to it tells it exactly what to do and how to do it, there's no complex input processing in the transmission electronics.
I did over simplify what the MLPS does. When the MLPS says X and the ECU logic goes into a loop where it forgets all the automatic stuff and just powers the solenoids for X (well, unless X is D obviously). It doesn't directly power anything, the ECU sees a particular voltage range and is programmed powers the solenoids that correspond to that range in response to that voltage.
IIRC line pressure is directly set by the resistance across the TPS but after some Googling it looks like that signal isn't what's passed directly to the transmission and that Mark was right. Still isn't a waveform (PWM or analog) signal though.
It might as well be a stealth bomber to the "points and a carb" guys on here but someone who's doing their research to figure out what they're working with will have a lot less research to do to understand the E4OD than to understand (to an equivalent depth) most systems since bus architecture became a thing.
I did over simplify what the MLPS does. When the MLPS says X and the ECU logic goes into a loop where it forgets all the automatic stuff and just powers the solenoids for X (well, unless X is D obviously). It doesn't directly power anything, the ECU sees a particular voltage range and is programmed powers the solenoids that correspond to that range in response to that voltage.
Even then, that's still not right. The computer will see that you've requested manual 1/2, will determine if downshifting to that gear will result in engine overspeed, and will also modulate the EPC solenoid as well.
IIRC line pressure is directly set by the resistance across the TPS but after some Googling it looks like that signal isn't what's passed directly to the transmission and that Mark was right. Still isn't a waveform (PWM or analog) signal though.
There is a monumental amount of stuff that goes in to determining line pressure on an E4OD. There are over 30 different parameters to determine line pressure alone!
Even then, that's still not right. The computer will see that you've requested manual 1/2, will determine if downshifting to that gear will result in engine overspeed, and will also modulate the EPC solenoid as well.
There is a monumental amount of stuff that goes in to determining line pressure on an E4OD. There are over 30 different parameters to determine line pressure alone!
"Over 30" sure sounds a lot like "not directly" to me. Do all calibration strategy families include overspeed protection?
"Over 30" sure sounds a lot like "not directly" to me. Do all calibration strategy families include overspeed protection?
You bet. Here's an except from the internal Ford LHBH1 Strategy document, which covers most speed-density E4OD V8 trucks. I'd imagine Mark Kovalsky would have seen or participated in the creation of this document. This particular except is the "PRNDL = 1 Logic", or when you put the transmission into manual 1st.
The part of interest are the 4 lines at the bottom. All 4 of those statements must be true for GR_CM = 1 (Gear commanded) to be set. The line of note is the very bottom one "VSBART_RT <= VS21PI". That line basically states the current vehicle speed must be below or equal to the maximum 2-1 downshift speed in order for 1st gear to be commanded.
So if you put it in 1st at 70 MPH, it will immediately downshift to 3rd, downshift to 2nd when appropriate, and when vehicle speed is finally low enough it will go into 1st.
whereas the E4OD's inputs are all external, the wiring harness running to it tells it exactly what to do and how to do it, there's no complex input processing in the transmission electronics.
That's just plain wrong. There is no other way to describe this.
Originally Posted by arse_sidewards
I did over simplify what the MLPS does. When the MLPS says X and the ECU logic goes into a loop where it forgets all the automatic stuff and just powers the solenoids for X (well, unless X is D obviously). It doesn't directly power anything, the ECU sees a particular voltage range and is programmed powers the solenoids that correspond to that range in response to that voltage.
That's just plain wrong. There is no other way to describe this.
The MLPS is just one of the inputs to the software. For example, say the truck is doing 80 MPH and the driver moves the shift lever to 1. Does the stupid electronics change the states of the shift solenoids to first gear? NO! The software looks at vehicle speed and says it can't go to first gear at that speed. It goes to second gear, which IS available at that speed, and shifts to first gear when the truck slows enough to safely go to first gear.
Originally Posted by arse_sidewards
IIRC line pressure is directly set by the resistance across the TPS but after some Googling it looks like that signal isn't what's passed directly to the transmission and that Mark was right. Still isn't a waveform (PWM or analog) signal though.
As pointed out above TPS is just one of the signals that is used to determine line pressure. The PCM calculates and estimated engine torque and that is the main contributor to line pressure, not TPS.
And yes, Mark is right. I worked with this software from 1988-2007. I will unashamedly say that I am familiar with how it works.
[QUOTE=Lead Head;16485856]You bet. Here's an except from the internal Ford LHBH1 Strategy document, which covers most speed-density E4OD V8 trucks. I'd imagine Mark Kovalsky would have seen or participated in the creation of this document.
The part of interest are the 4 lines at the bottom. All 4 of those statements must be true for GR_CM = 1 (Gear commanded) to be set. The line of note is the very bottom one "VSBART_RT
Yes, that's what I worked with in my time at Ford. On the tunes that I was responsible for I set the transmission parameters (THOUSANDS of them!) for every aspect of what the transmission did. If it was a tune that I worked on, EVERYTHING the transmission did was a result of what I input to the parameters such as VS21PI, which means, "Vehicle Speed for a 2-1 Pull In. A pull in is a downshift where the shift handle is moved.
For those interested, here's the complete table of contents describing the software logic that operates the E4OD. There are 166 pages of logic diagrams and explanations of what the software is doing. 48 pages just for pressure control! While the E4OD itself might not have that much going on electrically, there isa lot going on inside the software.
While the E4OD itself might not have that much going on electrically, there isa lot going on inside the software.
That's exactly my original point. It's not very complex by itself. You can abstract away the specifics of the calibration and just say that the transmission does what it's told by the ECU. Yes there's fairly complex logic and input processing that determines how the ECU controls the transmission but it's not part of the transmission as far as someone trying to diagnose an issue with the transmission itself cares.
Okay, but that applies to any and every single automatic transmission. They do what they're commanded to do. Many issues with the E4OD are electronic in nature, rather than mechanical, so understanding how the logic works is an important aspect in diagnosing issues with it.
