A Modest proposal for those 5R55E Owners - EPC Solenoid Replacement Proposal

[BrooklynBay]

Generally, a PWM signal would be a constant voltage, and current, but the time on/off cycle would vary. This is a little different. It looks like a constant frequency (possibly the carrier), but a varying current.

 

[dogfriend]

In other applications, Ford uses a constant voltage and varies the pulse width to control the current (power) sent to the actuator. I think that is the case here.

Current = electric charge / time; Amp = Coulomb / sec

 

[BrooklynBay]

Is that the same for the TCC, and IAC solenoids? I think they are all controlled by PWM.

 

[dogfriend]

Is that the same for the TCC, and IAC solenoids? I think they are all controlled by PWM.

I know that the IAC and the Transfer Case clutch work this way; I don't know about the TCC, but I think Glacier posted in another thread that it is modulated.

 

[dogfriend]

I found this in my service manual:

 

[Glacier991]

You guys have it all figured out. I wish Allbert could show the brass that we are not a bunch of shade tree mecahnics out here anymore... but some pretty sophisticated users. Kudos to you two.

 

[97greenmonster]

Yea, I like the new design solenoid alot.. Hoping this will work!

 

[OZY EXPLORER]

Any chance of sending one of those solenoids this way to Australia. I've just done a 110k mls motor change and the 2-3 flare has started to show. After owning a 1999 ex for 5years it’s had to find local mechanics with enough know how to do repairs. I do all my own work including the motor swap with help from this site. Next project is a gearbox flush with synthetic oil, filter and hopefully a solenoid change.

 

[BrooklynBay]

With the popularity of this thread, maybe it should be a sticky until after this test is completed?

 

[Nocturnall]

Count me in as well. I've been thinking of doing a rebuild on my VB and would be nice to NOT put in something that I know is going to fail. I have the begining stages of the shift flare for 2 - 3 and have some delayed shifts it other gears which goes away when I give it more gas revving the engine higher before shifts so I'm assuming it's a pressure/leakage problem.

 

[Glacier991]

Brooklyn... good idea. Now having stickied it, I want to mind everyone that this is a "possible" thing in progress. There has been no commitment or promise of any kind to do this on the part of the company - at all..... But I now have about 30 interested folks lined up and I am hoping that Allbert can convince the powers that be....

 

[Allbert]

Oh, I was thinking that it was supposed to compare the two designs. It is basically showing that Pressure is inversely proportional to Current applied. If it were perfect, it would be a straight line. What is the significance of the two curves (uncertainty?)

I apologize for not popping in here sooner... I didn't realize there'd been as much activity on this thread.

The separation between the upper and lower lines in the pressure vs. current chart is what we call "hysteresis". The upper line is the control (output) pressure as the current is increased, and the lower line is the control pressure as the current is decreased. The separation results from mechancial friction between moving parts and from some low-level temporary magnetization of the steel in the magnetic circuit.

The 292Hz frequency that I reference is because the power source we use on our test stand is a PWM type driver that we can vary the frequency on to try to mimic the signal that the vehicle would control the EPC with. 292Hz is actually a pre-set GM frequency (used in pre-2003 4T40/45/65E transmissions), but it yields roughly the same level of current ripple as I measured in our Ford test vehicle. The actual frequency of the current ripple in the vehicle was around 208Hz and was about 200mA peak to peak when the average current was around 830mA.

With respect to the wild pressure fluctuations shown in the other graph, I don't presently have any data to suggest that this ever actually happens in a real transmission. The test I did was a bench test to compare the relative stability of our design vs. Bosch's, and it was really just intended to give us confidence that our part is at least as stable as the original. If the results had come out the other way around (Bosch stable and ours unstable), then we would have had to make some improvements to our part OR verify that there is an appropriate level of damping in the transmission to to make sure our part would work OK. Since our part appears to be inherently more stable than the Bosch though, we don't have to worry.

 

[BrooklynBay]

Do other manufacturers like GM have similar symptoms with their EPC solenoids, blown out gaskets, and loose valve body bolts?

 

[dogfriend]

The separation between the upper and lower lines in the pressure vs. current chart is what we call "hysteresis". The upper line is the control (output) pressure as the current is increased, and the lower line is the control pressure as the current is decreased. The separation results from mechancial friction between moving parts and from some low-level temporary magnetization of the steel in the magnetic circuit.

Thanks for the explanation. Can you tell how much of the difference is mechanical friction vs. inherent magnetization effect?

 

[Allbert]

Thanks for the explanation. Can you tell how much of the difference is mechanical friction vs. inherent magnetization effect?

That's a bit of a trick. At our headquarters, we have what we call "force sleds" where we try to measure the magnetic force (vs. stroke at various currents) of the "motor" sections of solenoids. These allow us to measure how much force it takes to manually (via micrometer screw mechanism) stroke the armature from one end of its travel to the other and back. By measuring the hysteresis that results from stroking the armature with no current applied and comparing that to the hysteresis that results when we stroke the armature with current, we can somewhat determine how much is mechanical vs. how much is magnetic. However, when we energize a solenoid so that there is magnetic force present, the magnetic force usually pulls the armature not only in the desired axial direction, but also against its bearing in the radial direction, and this "side loading" increases the mechanical friction somewhat which makes it difficult to truly separate the magnetic hysteresis vs. the mechanical. Still, the data is usually good enough that it can lead our engineers to try to improve either the magnetic qualities of the part or the bearing system as needed.

 

[97greenmonster]

This is intresting, i never realized a solinoid did that. seeing the graphs alone made me like it, but understanding that this new part is more stable makes me want in even more.. thanks alot Allbert for possible bringing us 5R55E owners a better shift! Thanks!

 

[Allbert]

Ok... I just cannot constrain myself. I HAVE to post a couple graphs.... been too long.... my graph posting finger is itchy...

Allbert sent this graphical superimposition of the 5R55E modulated valve performing overlaid on the "new design - old style" EPC being proposed.... Ya know how I say that the EPC's modulation is a killer for it? This puts it in perspective. Which one would you prefer in your tranny?

Just to be clear... the Bosch pressure oscillations shown in the graph here are not the result of any current signal... the current is at 0amps (i.e., no electricity) during this test; it's all hydraulic. What is happening is the EPC spool has begun to resonate somewhere near some natural frequency of the system because there is not enough energy-absorbing material in the output side plumbing and the pressure is bouncing high and low. It's kind of like that water-hammer effect that you can get in household pipes. In the valve body, some downstream valve usually strokes some distance in response to a pressure change from a solenoid, and as I understand it, these valves have some viscous and friction damping of their motion which can absorb the energy of the pressure waves so that it is not reflected back to the solenoid where it can cause this kind of activity. As clearances increase and/or temperatures go up, however, the amount of damping provided by a valve might decrease to where a solenoid's natural instability may cause symptoms. Like, I think in the case of the older AODE transmissions, for example, improper adjustments to the EPCs might have been responsible for altering the stability of the devices such that they would sometimes overwhelm the natural damping of the valve body and cross the threshold into resonance.

As always, I'd love to hear from anyone out there who might be able to explain things better than I have here. I'm not sure I've done the subject justice.

 

[Glacier991]

For those who have read my posts and threads and Diaries.... what have I always advised regarding the EPC adjusting screw? Don't! Now you have a good reason why.

 

[timgie]

For about a week the OD light on my 95 explore was blinking and the shifts were hard. This all went away before I could get the car to a mechanic. The mechanic told me the tranny codes indcated I needed replace the tranny.

Would changing out the Selenoid be be a reasonable fix? If so, sign me up.

Tim

 

[BrooklynBay]

Welcome to this forum! What were the codes?