2nd Gen Non-Engine/Transmission Mystery Switch Options

[Vaughn MacKenzie]

I want to install a trans TC lock switch on my '01, but I want to use a momentary push button that will manually activate lockup when I press it, and for it to automatically unlock either by touching the brake pedal or letting the normal TC control signal do it. I think I'd prefer to have it disengage with the brake pedal because normal operation is for it to unlock letting off the throttle, which defeats half the purpose. Anyway it would basically mean adding at least one relay but beyond that I'm not sure how you'd do it.

I saw this diagram, maybe it's what I need, but I didn't find any description of how this setup would function. It looks like it uses a momentary switch for forced unlock as well but I don't know how it would resume "Normal" operation.

Vaughn

 

[Joe G.]

The switch in that diagram is not a momentary push button. It's a single pole double throw with center off toggle switch. In order to use a push button you will also need some sort of flip/flop circuit and an indicator light that keeps track of the on/off condition of the circuit.

 

[Vaughn MacKenzie]

Thanks Joe, I thought the switch was SPDT momentary since it's labeled "mom. " Will do some googling on flip flops. . .

 

[Joe G.]

Even if the MOM does mean momentary I don't think the circuit would work. For one thing with no indicator lights you would not know what was going on. A flip/flop is an electronic thing. Originally invented using a tube, but now can only be purchased on an IC. There are a bunch of varieties of the circuit so you need some electronic knowledge to make heads or tails from what you read.

I know how to do that kind of stuff, but my lock up system uses switches rather than electronic gadgets. I use a Radio Shack 12 volt LED to indicate when lockup is forced off so be consistent with how the OD light works. The position of the toggle switch indicates if the lock mod is in use or not.

An old fashioned floor mounted dimmer switch is a mechanical flip/flop switch.

 

[Allnew2Me]

This is a schematic that member Jaybo came up with a long time ago and it works. The 50 ohm resistor acts as a dummy load so the PCM "sees" the transmission and doesn't throw a code. The relay simply allows the use of a smaller in-cab switch but could be exchanged for a DPDT switch. I have used it on my 01. 5 and can say that it works as designed.



http://home.pacbell.net/jaybo/image2.gif



To use it the way you describe you will need to use a locking relay that takes the place of the lockup switch in Jay's drawing. This relay will perform the function of activating the TC lockup, and also apply power to itself to lock itself on. By using another SPDT relay and using the normally-closed contacts of this relay, you can activate this second relay with a power source from the braking circuit that will energize the relay, but because you are using the normally-closed terminals, it will actually open the locking circuit that supplies power to the first relay, releasing the power to the first relay and unlocking the clutch.





Another option, although more expensive, is to buy a BD Torqloc controller which has a TC lockup position that allows you to lock the TC clutch and releases it upon reaching a preset lower MPH limit. It keeps the clutch locked but it won't do the 4-3 downshift locked so you have to disengage the OD so the truck doesn't shudder upon slowing.

 

[Joe G.]

The momentary thing was what I was saying would not work. I can see that it will work with a normal toggle switch, but as shown above I don't think the momentary will work.

 

[Road Dog]

I was curious so I picked apart the circuit by redrawing it a relay ladder logic.

Relay TCR is a latch. When DS (dash switch) is LOCKED or the TC signal is grounded then it latches holding the TC signal at ground.

Relay BR handles the brake signal. When energized it energizes relay AUR.

Relay AUR unlatches relay TCR. When the brake is pressed or DS is UNLOCK then relay AUR energizes and unpowers relay TCR on the ground side.

-- Once locked the torque converter remains locked until the brake is pressed or the dash switch is UNLOCKed. (I think the TC normally unlocks when you lift off the accelerator. )

-- If the torque converter is locked via the PCM then relay TCR will remain latched even if DS is UNLOCKed or the brake is pressed.

-- The BR relay is there to isolate the brake circuit from the transmission circuits and avoid any electrical weirdness.

 

[Allnew2Me]

The momentary switch will work as it just activates the relay that activates the lockup schematic. The power that holds this first locking relay locked is cut by the second relay when the brake pedal is pushed, activating this second relay which opens the circuit that holds the first relay closed.

 

[Allnew2Me]

Here is the schematic from Jaybo

 

[Vaughn MacKenzie]

Road Dog that is pretty cool, thanks for deciphering that for me!



Thanks for the schematic too Allnew2me, what you say makes sense replacing the lockup switch with a latching relay and controlling it with a momentary switch, but as for the brake circuit is it normally High (energized) until you hit the brake pedal? I guess I was thinking it was the other way around. Anyway I could do the attached relay setup in place of the switch if I understand correctly? I would prefer this method as it would involve less wiring than doing the 3-relay setup.

 

[AClayton]

I tried using the 'mystery switch' at first. I just manually locked the convertor and was always aware it was locked and drove accordingly. The problem is when someone else drives your truck, it is too complicated for them to understand and things go bad quick. My ex-wife was ratchet-jawing and sub-consciously forgot to flick the switch to unlock the TC. The Cummins finally did stall but only after leaving her vulnerable right in the middle of the intersection.



I purchased the ATS Co-Pilot and have been happy with it ever since. That was 4 yrs ago and it has been very reliable and really helps with the towability of the truck. I understand the circuit you have is much more advanced and will work but I prefer to keep the convertor locked all the way down to 20mph and downshift to utilize the EB. I always rev slightly when downshifting to combat the harshness of the gearchange. Again..... not for everybody, but once you tow with that convertor locked, the towing prowess is addicting! I just don't like the mushiness of even a modded transmission when towing heavy.



When the truck is unloaded, you simply raise the mph setting to stock and let her go... ... ... ... and anybody can drive the truck!!







Alan