2nd Gen Non-Engine/Transmission Goof-Proof Mystery Switch

[Boldt's Wagon]

I have installed a "Mystery Switch" to lock the torque converter clutch that uses a 15 psi Hobbs pressure switch to open the connection to ground when you slow up (less than 15 psi boost). The Normally Open (NO) pressure switch is in the electrical line from the manual Mystery Switch to ground. Thus, the Mystery Switch provides another ground for the torque converter clutch only when the boost is over 15 psi and cannot keep the TC locked at less than 15 psi. .





I used a Radio Shack Double Pole, Double Throw (DPDT) switch (on-off-on) to provide three functions.



Up - TC lockup with boost over 15 psi and stock performance under 15 psi.



Center - No TC lockup available (TC lock off)



Down - Stock TC/transmission operation.





The wiring for the DPDT switch with the terminals for each pole being numbered 1, 2, and 3 with number 1 on the top.



The wire between the PCM and the transmission is cut and spliced into the DTPT switch as follows:



From the PCM (stock ground) a new wire extension is connected to Pole 1/terminal 1 and Pole 2/terminal 2.



From the transmission a new wire extension is connected to Pole 1/terminal 2.



A new wire is connected to a new pressure switch to Pole 1/terminal 3 and Pole 2/terminal 3.



The other terminal of the Normally Open (NO) pressure switch is connected to ground.





I connected the pressure switch in the line to my boost gauge with a tee.





Note, this is probably only recommended for stock or mildly bombed rigs. DTT/Bill Kondolay offers a Smart Controller that unlocks the TC at high power levels to protect the TC clutch with very high torque engine modifications. If you only want a Mystery Switch for pulling a trailer up grades without the TC unlocking and building heat this should work without the worry of forgetting the switch and damaging the TC clutch when you come to a stop with the TC clutch locked up. Goof-Proof.

 

[Dennis Garrett]

I use the same lock up switch on my 97, but without the pressure switch. I drive by it 100% of the time. Center off, forward it locks, all the way back is stock.

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[Motorhead]

Are you then able to lock the convertor in second,like when pulling a hill with a trailer? Can the stock convertor handle this with a stock truck? Chris

 

[Joe G.]

Boldt's Wagon,



If it unlocks at 15 PSI or lower what keeps it locked on a downhill with the exhaust brake in use? That's why I have a manual lockup control (AKA mystery switch) in the first place. The exhaust brake is worthless without it.

 

[Boldt's Wagon]

No exhaust brake, I use 2nd and 1st gears for downgrades of 6 percent or over. My mystery switch application is for keeping the TC in lockup while climbing the grades keeping the transmission and water temperatures in control.



This should lock the TC clutch in 2nd as long as you maintain 15 psi or over, I have not tried it. I have the DTT torque converter and lockup is obtained by rolling off the throttle. I do not know if the DTT TC can be rolled into lock without dropping the boost below 15 psi in 2nd. The stock converter would go into lockup at higher boost.



If I remember correctly, there is also a 6 psi NO pressure switch. The 6 psi switch might be a better choice for a TC lockup/release point.