I'm considering swapping in an E4OD but relying on the electronics concerns me. Can an E4OD be hotwired as a limp home mode and diagnostic tool? Something I could setup for if the computer or something else fails to have rather simple switches and/or rheostats to control the valving and get my self home and or bypass malfunctioning valves.

Or.. am I crazy to think this, just going to damage something, and should put in a manual?

 

I really don't understand what you want to do. If you mean a setup to get you home if the electronics fail, that's already built into the trans. If there transmission connector is unplugged, or the power turned off to this connector the trans will default to fourth gear with an open torque converter. You can drive it home this way.

I know of a person that had a 6.9L E4OD van that drove for over 10,000 miles like this until he found a dealer tech that was smart enough to figure out that the van was built without the computer.

 

That's good to know, but what do you mean "built without the computer" like a PO put the tranny in but didn't realize he needed the computer?

FWIW this would be behind an IDI diesel.

What I would want to build would be a kind of I guess you could call it break out box. A box/switch panel that in the event of a failure could be plugged in in place of or interrupt the computer to provide temporary rudimentary control/override.

Example, total computer failure but I'm off road and need 1st with engine braking. So I unplug the comp, plug in this panel and then could just flip a couple switches for the 1st gear solenoid, coast control clutch, and maybe the converter lockup once moving.

Example, placed between computer and transmission to override/interrupt certain functions. Say reverse starts slipping, so when in reverse I flip a switch to remove the signal from the EPC to maximize pressure. Or is this moot as the EPC only releases pressure mid shift or idle or something where anytime there is torque it's at full pressure?

In the extreme could this be taken to the point of providing useful manual control. For example I imagine a shifter with a squeeze handle that operates the EPC, squeeze handle to soften shift, move to shift, release and have full pressure. Then a thumb operated switch for the TCC.

If this kind of stuff is possible I'd think it the ideal setup when it comes to capability and reliability over the C6 with a manual valve body I have now.

Also it would of course be good to know what the computer will do if it loses a single input signal, for example if it loses the VSS signal will it default to RPM/TPS signals and still provide control?

 

No, the assembly plant built the van without a computer. The computer only controlled the transmission in the IDI diesels, so the van ran and drove without a computer. The trans was always in fourth gear. The owner complained that it was a dog, but he had never driven a diesel before and just thought that's how they were.

Yes, that could be done. You need this chart to determine which solenoid is on for what gear:


The EPC is rarely at full pressure. The pressure is controlled mostly as a function of torque. You could get max pressure by opening the circuit. If you do that when the shift lever is in the 1 position you will blow up the forward drum. It can't handle that much pressure.

That is pretty extreme. I see a problem with that. How good are you at measuring slip time on the clutches on the go? If the nominal slip time is 0.500 seconds, and you soften the shift a bit and slip time goes to 0.600 seconds will you notice the difference as it is happening and firm it up to keep the slip time at 0.500 seconds? If not you will be replacing that clutch in a short time. They don't like slipping.

There are failure mode actions built in for every signal. If you have it connected like the stock system it can compensate for loss of signal. It will also set a code and flash the OD OFF light, assuming you have one.

 

Thanks Mark for the input, you're exactly the guy I'd want to ask these questions of, I read much of the "E4OD Operation" thread and as hoping you'd pop in here.

WOW, woops

I didn't know there was anywhere the E4OD and 6.9 overlapped must have been the very last 6.9 and very first E4OD in 87/88. Doesn't matter just interesting.

IDK about that one, but there's one you posted in the "E4OD Operation" thread that I saved and this http://www.nloc.net/photopost/data/2...pplication.gif

That's details though, I'm just in the preliminary thinking stage, the C6 isn't cutting it anymore.

That's some very important information, leads to a few questions though.

What's different about the shifter being in the 1 position, does it open a valve to provide full flow/pressure to the forward drum?

Isn't the forward drum engaged in all forward gears, but this is only an issue in the 1st position of the shifter?

In the example of the van with no computer wouldn't the pressure be full so if he had put the shift lever in 1st what would have happened?

Also with the van, without a computer what happens when the lever is manually shifted? Would/was he able to manually shift 1,2,3/D, OD?

Uhm yeah I know that's extreme, just thought I'd put it out there. Like I said, all preliminary, I just need to decide if I want to go down the E4OD road and this is the part I have the least info/options on. That kind of stuff I'd certainly tread lightly and learn learn learn with extreme caution, I have no interest in killing my transmission by screwing around. A big part of why I'm asking this stuff.

Of course, if I did this I'd either swap in a E4OD column or add a light if I used a floor/aftermarket shifter.



Bottom line I'm thinking at this point you have an idea what I'm getting at. I'm very much about reliability/redundancy and just want to know that I can have a backup plan for as many failures as I can be ready for. Nothing is 100% reliable but I think if this kind of thing is doable then an E4OD could be more reliable then a manual or even C6.

 

It was an 89. Maybe it was a 7.3L, I don't remember. I do know it was an IDI engine. Engineering got involved with this, which is how I know about it. We kept asking the tech if there were codes and he kept telling us there were no codes. If he had been smarter he would have said that it wouldn't respond. It would output a code 11 if everything was fine.

That is a band and clutch application chart. It doesn't tell you solenoid states. You need the chart I showed above to get the solenoid on/off conditions.

There is a boost valve in the valve body that raises the pressure when the shift handle is in the 1 position.

That's correct.

He would have blown the forward drum apart. He was like most people, the shift lever never moved below OD.

In 1 & 2 you get 2. There is no 3/D position. In OD you get 4.

 

I was mostly referring to the one you posted well over a year ago here https://www.ford-trucks.com/forums/1...l#post12716011

Very interesting and useful information.

So with complete electronic failure shifting to 2 will get me 2 no matter what but shifting to 1 will blow it up, now THAT is need to know.

Then a good backup for complete electronic failure would be to have a 1st switch/electric bypass/backup that would turn on SS1 and provide limited power to the EDC if/when the shifter moves to 1st. Or would the best way to get 1 with complete failure be to shift to 2 and just power SS1?

Maybe a buzzer and warning light that will go off if when the shifter moves to first and there is no power to the EDC would be a great idea to prevent blowing the forward drum. And/or Is there a place to tap into the pressure to the forward drum? If so maybe a safety blow off valve is a very good idea there?

How about reverse with complete electronic failure? When shifted to reverse the reverse clutch is activated by moving the shifter but when working properly SS1 is activated, with no power and thus SS1 and 2 off it's in 4th, so with complete electronic failure and shifter in reverse do you get OD reverse? In simple terms did the guy with the van have OD reverse when he shifted to reverse?

If true then a switch for SS1 would be really useful for reverse in event of electronic failure.

Does this mean if I can control the shift solenoids I can get reverse in any gear?

Edit, that reverse theory can't be right cause of how the gears themselves are multi purpose, I have no idea what it would do.

 

No, it won't blow it up. Without power when you put the shift handle in 1 you get 2. That doesn't raise the pressure and blow the forward drum.

I don't see how a buzzer and warning light would work. By the time you recognized that the buzzer had sounder and the light was on the damage would have already been done. It doesn't take long at all.

Reverse works with no electrical power. I forget the mechanism, but I think there is a hydraulic circuit that turns off the OD clutch. It's been too long, I don't remember.

 

The way I figured the buzzer was an assumption that even in first and at 0 power to the EDC pressure wouldn't climb high enough at low RPM.

I don't want to ride you or anything, you've been very helpful but you realize these two posts contradict each other?


However all in all these details are moot at this point. I'll figure that out when/if the time comes. The only remaining question is one of complication in being able to use simple electronics to do some of these overrides.

I read the EPC is a 1 amp max but where is the resistance, what are the voltages into the EDC, is it to sensitive to be rigged up with simple rheostats, resistors, relays if I had to?

IIRC what I've read the TCC isn't picky, 12V works?

The shift solenoids, 5V, 12V, amp limited, etc?

 

No, you're right.

I had to think about this. It's been almost 20 years since I worked on this, the details are getting a little fuzzy in my CRS* brain.

I was working with an off-road race team trying to get them to run an E4OD in their stadium truck. Computers were not allowed on the truck. I rigged a system that used the TRS to actuate the shift solenoids so that it would have first when the lever was in 1, second in 2, and 3 in OD. They didn't go fast enough to need fourth. When we tried it the forward drum blew apart. We didn't control EPC at all, just left it at maximum.

Then I asked someone with more E4OD experience than I had and he told me that was to be expected. The production valve body has protection so that won't happen.
I think that will work. How you would determine what pressure you need isn't at all clear to me.

Yes, +12v to one side and ground to the other and it's happy.

They are 12v. One side power, the other ground.

With both the TC and the shift solenoids polarity matters.

 

Just for the sake of brainstorming cause I like solving things like this.

With the limited info I have now I envision a system that uses two throttle position sensors(TPS) a 5 pin(double throw) relay, and a resistor. I don't know the internal resistance of the EDC though.

The relay and resistor is just to add a power path to the EDC through the resistor when in 1st to drop pressure in 1st.

The two TPSs are wired in series,

The 1st TPS is attached to the throttle but back words, so max resistance with foot off the throttle, of course adjustable. This makes for a simple WOT = full pressure linear adjustment of the EDC.

The 2nd TPS is attached to the shifter detent this is a little more complicated. Detent uses a spring and plunger that is extended when in gear and compressed between gears. Attach TPS so when the plunger is compressed the TPS provides higher resistance. This makes for a split second pressure interrupt between gears all adjustable of course.

 

Why the split second pressure interrupt between gears? What does that do for you, except maybe wear the clutches faster?

 

Because...
A WOT full pressure shift would be very harsh.

 

How will you know how much to reduce the pressure? Too little pressure and the clutch gets destroyed. Too much and the shift slams. The PCM calculates engine torque in real time and adjusts pressure a few times per second to always have the right pressure.

 

I can't initially it would have to be trial and error, erring on the side of too much, and adjustable on the fly.

Have a pressure gauge that is watched when run by the computer and copied. Maybe even with data acquisition.

However this leads to a question, how fast does pressure respond to changes in EDC voltage? If it's all but instant then it matters less.