Mytery Switch with Pedal and Pressure Switch complete and WORKS!

[Yo Hoot]

2004 Mystery Switch with Pedal and Pressure Switch complete and WORKS!

I finally got around to installing my "Mystery" Switch.



I found a nice pedal switch at Harbor Freight for like $10 or so. I cut the cord off and rewired the internals. Then I used the cord plug for the "out" connection. Real easy. Mounted the pedal on the floor up by the e-brake pedal.



I installed the Hobbs pressure switch that I mentioned earlier.



I decided to do the relay mod instead of the resistor. I pulled the trans relay (#59) and put a small wire, wrapped onto each pin of #30 and #87. Pushed the relay back in place... . no solder required.



Works like a charm. I can hit the pedal at a stop. It will lock up as soon as it gets to about 10-15 mph. Anytime it's chugging more than I like I just hit the pedal once more to unlock.



Downshifting is not pleasant. I turn it off as I'm slowing down. I see me using this more for pulling my 10,000 lb trailer up the steep hills to keep the trans temp down.



Harbor Freight Pedal

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Posi-Tap "T"

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[AH64ID]

To show my ignorance to the way of the slush box... What does it do?

 

[Yo Hoot]

To show my ignorance to the way of the slush box... What does it do?

That's why we call it the "Mystery Switch" LOL

It's a torque converter lockup switch. It allows me to lock up the TC on demand, overriding the computer at any time.

The pressure switch is mounted on the gov port that increases pressure as you go faster. By hooking the pressure switch up in series, it won't allow the switch to work until 10-13 lbs of pressure is present. This helps with forgetting to turn off the TC lockup when coming to a stop.

The main reason I installed it is to reduce trans temp during pulling up steep inclines.

 

[AH64ID]

Gotcha, I kinda figured it was something like that.

 

[cerberusiam]

Pretty slick setup with the Hobbs switch and pedal.



However, the first thing you had better do is pull that wire off the trans relay before you have a melt down. An expensive one. Any short on the power feed to the solenoids or the solenoids themselves is going to let the smoke out of the FCM.



Just wire a 33 ohm resistor between the ground and your switch so the jump wire is not needed. Keeps the circuit protection in place so you don't fry the electronics.

 

[DaveHess]

Will this mod work with a 2003. 5 48RE when the PCM was separate from the ECM?

 

[Yo Hoot]

Pretty slick setup with the Hobbs switch and pedal.

However, the first thing you had better do is pull that wire off the trans relay before you have a melt down. An expensive one. Any short on the power feed to the solenoids or the solenoids themselves is going to let the smoke out of the FCM.

Just wire a 33 ohm resistor between the ground and your switch so the jump wire is not needed. Keeps the circuit protection in place so you don't fry the electronics.

Wow thanks for that tip. I don't recall that ever being mentioned before about the risk of the relay method. I'll switch it out.

Why does this create a problem?

DaveHess. . I don't know but others might.

 

[cerberusiam]

Will this mod work with a 2003. 5 48RE when the PCM was separate from the ECM?

Should not matter where the TCM is. We are completely bypassing the TCM\ECU control of lockup with this install.

Why does this create a problem?

The relay is the fail-safe on that circuit in case of issues. By passing with a wire puts the load back onto the FCM that activates the relay to keep the trans control operational. Those circuits are sensitive to over loads and spikes. It doesn't take much to mess them up.



Its much more critical on the newer ones because it can take out the TIPM and that ends being expensive to fix.

 

[Allnew2Me]

I see the Hobbs switch is set at 10-13 PSI and this will allow a lockup at 10-15 Mph.

Did you play with different pressure switches to achieve that result or did you guess what would work? I like that idea of having the TC auto-unlock but would probably want the lower limit to be closer to 20MPH. My BD Torqlok is set for 25 which is too slow to leave it in OD when decelerating, because it shudders pretty good if I don't turn it off first. But because it controls the exhaust brake it would be nice if it held to a slower speed and your system is slick for that.

Our transmissions won't downshift from OD to third with the convertor locked so you would have to manually turn it off, and I wonder if yours will shudder in third or second gear at 10-15MPH.

 

[monkeyman]

I don't know about your year, but there is an easier way on 2002 and earlier, there is a pin you buy from Cummins, it plugs into pin 20 on ECM,Cummins part number 3824810
it will allow ECM to control E Brake. I have a diagram but will have to scan it and post if interested.
Rick

 

[JJPage]

Our transmissions won't downshift from OD to third with the convertor locked

Mine will!

 

[Yo Hoot]

I see the Hobbs switch is set at 10-13 PSI and this will allow a lockup at 10-15 Mph.
Did you play with different pressure switches to achieve that result or did you guess what would work? I like that idea of having the TC auto-unlock but would probably want the lower limit to be closer to 20MPH. My BD Torqlok is set for 25 which is too slow to leave it in OD when decelerating, because it shudders pretty good if I don't turn it off first. But because it controls the exhaust brake it would be nice if it held to a slower speed and your system is slick for that.
Our transmissions won't downshift from OD to third with the convertor locked so you would have to manually turn it off, and I wonder if yours will shudder in third or second gear at 10-15MPH.

No I haven't played with the pressure adjustment yet.

One mistake I made is I assumed this pressure switch would allow me to add an LED circuit but unfortunately it's 2 circuit, SPST, normally open and normally closed. The spec sheet says a NO,NO is available but I still would require a relay to isolate the 12v.

I guess if I want to use this pressure switch I could use the normally closed side to operate a relay... just have to think about the relay type and what will actually be going on.

Here is the Hobbs data sheet...

http://www.alliedelec.com/Images/Pr..._INC/Hobbs-Inc_Industrial-Control_6113015.pdf

 

[Yo Hoot]

Yes I do get the shutter when slowing down with the lock on. I don't think its downshifting soon enough since it thinks th TC is unlocked I assume. That's the beauty of the foot switch. So easy to just tap it on decelleration.

 

[Scooby]

Well now that you have the right number of pedals down there - you should have just gotten a manual transmission!

 

[Allnew2Me]

Having the footswitch makes it easy to turn off the TC clutch without having to take attention away from driving while reaching for a switch. Unless you have a specific application I would guess that a lockup speed that was a bit higher would be an easier driving experience.



JJ, I will assume that your modified DTT trans allows yours to downshift from OD while locked. Mine, even though modified by Suncoast, still holds in OD while the TC is manually locked.

 

[JJPage]

JJ, I will assume that your modified DTT trans allows yours to downshift from OD while locked. Mine, even though modified by Suncoast, still holds in OD while the TC is manually locked.

Exactly! I installed a second switch to #6 pin, that locks it in OD.



I really like Yo Hoot's idea of the pressure switch in series with the TC lock, I was at a drive up menu board at a burger joint, I leaned over to speak, and my right knee hit my TC lock switch, I jumped forward about 3 hops before it killed my motor, not good.

 

[Yo Hoot]

Been driving it for a couple of days now... I love this setup. I do think I will adjust the pressure a tad higher so it unlocks automatically a few mph sooner.

 

[SDrake]

Interesting. I have to look up your earlier post about the hobbs spressure switch. BTW what is the round electrical connector above and to the right of the emergency brake. Something you added, or is it something on later model trucks? I imagine you could say, "Where have you been?" but then I would have to say, "I don't know. " and waste you time

 

[Yo Hoot]

That connector is for my snow plow controller.

 

[Yo Hoot]

After adjusting the pressure switch to disconnect at a higher mph, I took my trailer for a test drive. I don't like the higher mph cutoff when pulling up a steep hill. I could only get it to connect at 15mph with this model switch. It won't let me lock the TC soon enough in first gear. I think I'm gonna turn it back the other way and have it only disconnect at it lowest setting... around 10 mph. This way it's only used as a safety switch, not allowing TC lock from a standstill. I found that the system simply does not work well without intervention when slowing down. I think the TCM is programmed to treat the non-lock and lockup as two gears in a sense. In other words, if this was a manual trans you would let the rpms go higher before you shifted to the next gear. Since the next gear in this trans is normally starting in non-lockup, it shifts into it sooner than locks... kinda like a two stage gear. Because of that the shift points aren't good with a continuously locked TC. This is for normal use. Maybe a truck used for all out performance would like it.

The test drive showed that when pulling (8000#) a steep hill, especially when starting off on the hill, you tend to get a hunt between first and second, or TC on and off, when the TC is supposed to be locked. Now I'm not sure if it was the pressure switch causing this or it was trying to shift to second. I'm thinking the pressure at that port might be acting a little different when the trans is being loaded like that and the TC being forced locked. If the pressure drops at the pressure switch when (the switch) it's on the threshold, it will unlock and feel like a "hunt".

Next test I'll put a jumper on the pressure switch to take it out of the equation. Basically taking it out of the circuit. Pull that hill again and see if it's a little more stable. Basically I want it locked in first after I get rolling around 10 mph and hold steady.