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So I'm debating the mystery switch install since I'm laid off for the next few....days weeks whatever.  Does anyone have a video of actually driving using a mystery switch.  Not the install. That actual daily driving on camera. Think that'll help the wife understand when BusterBrown starts leaving packages on the porch.  

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I assume that you are talking about a switch that manually controls torque converter clutch lockup.  I don't have a video, but I think I can provide more information about how I used the switch than a video could provide.  Coincidentally, my truck that had the mystery switch was also a  '99 (with a stock automatic transmission and a stock fueled engine).

 

My installation was simple - one relay and one momentary floor switch operated by my left foot.  The floor switch was a durable, low profile switch that required very little pressure to operate, just the weight of my foot.

 

A couple of helpful things to know: 

 

  1.  A stock automatic transmission will only lock the converter in 3rd and 4th gear (overdrive).   

  2.  A stock automatic transmission unlocks the converter during a shift and then relocks the converter after the shift.

  3.  The mystery switch does not lock up the converter.  The mystery switch allows you to keep the converter locked up after the converter locks up on its own.  This is important to know, otherwise you won't be able to maximize the benefits of the mystery switch.

 

Behavior of the of torque converter lockup with mystery switch operation:

 

  1.  Fourth gear (overdrive), converter lockup, foot on mystery switch - converter will remain locked and transmission will stay in fourth gear (will not downshift) regardless of throttle position.  When mystery switch is released, the transmission operation will return back to automatic mode.

  2.  Third gear (overdrive), converter lockup, foot on mystery switch - converter will remain locked and transmission will stay in third gear (will not downshift or upshift) regardless of throttle position.  When mystery switch is released, the transmission operation will return back to automatic mode.

 

Driving the truck using the mystery switch:

 

Getting up to speed quickly from a stop - lock out overdrive (4th gear).  Accelerate moderately until transmission shifts into third gear.  Back off the throttle and let the converter lock up.  As soon as the converter locks up, depress and hold the mystery switch and step into the throttle and continue to accelerate moderately.  Pre select overdrive (the transmission will not shift).  Continue accelerating  to about 50 mph (this will be your shift point).  Back off the throttle, release the mystery switch.  You will feel the converter unlock, the  transmission shift into fourth gear, and the converter relock.  As soon as the converter relocks, depress and hold the mystery switch and accelerate moderately until you get to your desired speed.  You can now release the mystery switch since the converter will stay locked on its own.  With a little practice you will find the truck will accelerate quickly and shift smoothly.

 

Slowing for 45 mph curve – Depress and hold mystery switch and back off the throttle.  The transmission will remain in overdrive (fourth gear) and the converter will remain locked (even if the brake is applied).  Upon exiting the curve you can accelerate as hard as you wish.  Once getting back up to speed, you can release the mystery switch.

Approaching a steep uphill grade (downshifting to third gear)  Depress and hold the mystery switch.  Stay in the throttle as you approach the grade and preselect 3rd gear (lockout overdrive).  The transmission will not shift.  When you are ready to make the downshift, let the truck slow to about 50 mph.  Ease off the throttle and release the mystery switch.  The converter will unlock and the transmission will downshift into 3rd gear.  As soon as the converter relocks, depress and hold the mystery switch and use the throttle to maintain your speed.  Again, a little practice and the shift will be smooth.   

Downgrades – 3rd or 4th gear – Select whichever gear for the downgrade.  After the converter has locked, depress and hold the mystery switch for the duration of the downgrade. Brakes can be applied to help maintain speed. 

Once these techniques have been practiced for awhile, the mystery switch operation will become second nature and you will be using the switch without thinking about it.

Hope this is what you are looking for.

- John

 

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  • 2 weeks later...

I  did the switch last week, just used a switch and a relay to keep it on once it's locked, I also used the actuation coil on another relay in place of the 30 ohm resistor, the resistance on the relay coil is  higher than 30 ohm but up to now it hasn't set a code but I now have resistors if needed, all in all it works just fine, didn't really want it unlocking on braking so thats why I just used one switch.

I have read posts where a relay is jumpered and then the switch will lock whenever,  this would suit me better but I have a standard torque and trans so wouldn't suit the trans I doubt

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5 hours ago, wil440 said:

the resistance on the relay coil is  higher than 30 ohm

All the coils in the mini ISO type  relay I've tested have been between 70 and 90 ohms, 

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40 minutes ago, IBMobile said:

All the coils in the mini ISO type  relay I've tested have been between 70 and 90 ohms, 

I also used a mini ISO and OHMS where around 75 give or take on 3 I checked, I decided to try it as I have a scanner to turn off any codes so no harm done if a code was set and I figured whatever the 30ohm resistor was there to mimic it just might have been a coil :), it hasn't set a code yet and I have a million 30 omh resistors now..... can't buy just one or 5 or something normal but they were only £2.00 posted, I can say with hand on heart where they were made :rolleyes:

Also a relay was rather easy to do as I have an AUX fusebox from a Ford car fed from the now unused large  fuse at the PDC it sits just below the cup holder, it's modular and I just snapped in the ISO relay holder and job done, it has the capacity for maybe 20 relays both ISO and normal and maybe 70 fuses in 3 seperate modules which all snap into the mounting bracket.

I did contemplate using a varible resistance 5 position switch that I had that I originally used to control a set of rad fans on a 71 roadrunner but after measuring all 5 positions the ISO was in the middle so used that instead first and up to now no code so all good, I've only done a few miles in the truck where I was able to use the lockup switch due to the whole country  being in lockdown so the food supermarket is only 3 miles away, I may well try the trans relay jumper as the PCM locks at just over 30mph and in 4th at about 45 to 48 ish I think, these are both a little high for our speed limits which are 30mph in built up areas,  the next is 40mph then 50, 60 and 70 so its not quite right for the 30 and 40 limits

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2 hours ago, IBMobile said:

Lock out overdrive, then engage the convertor lock up for 3ed gear, see how the feels.  

This is what I've been doing for our 30mph limit but the PCM locks in 3rd at a little over 30mph so I have to drive over the limit to get it to lock, once locked and switched I'm ok but I may try the jumper and if I read it right it will lock on the switch no matter what, I could then lock at high 20's and in 4th just around 40

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