Engine/Transmission (1994 - 1998) What is a "Mystery Switch"?

[AMink]

I know it has something to do with the transmission, but what exactly does it do? Thanks

 

[TSRAM]

A manual lock-up switch for your converter. It can help you and hurt you if you get carried away with it. It'll help keep your transmission in lock-up if it jumps back and forth when towing and etc. , but you can hurt the tc if you forget and leave it engaged when stopping.

All you have to do is run a toggle switch with a wire going to a solid groung on one side and to the correct wire to the wiring harness at the pass. firewall.

 

[dalton4]

It is a grounding switch that is tapped into the tc wire that controls lock up functions. Using the switch and making ground contact will force lock up. transmission will not down shift if in forced lock up and will stall the engine when coming to a stop. Suggest you do a search for more info on topic relating to proper use. The switch can do damage if improperly used.

 

[AMink]

Thanks for the info.

 

[y-knot]

In truth, it is a very crud way to by pass the system of checks and balances and manually lock the transmissions torque converter. I personally think they are unsafe for both truck and occupants. Anytime you override a system and erase all safety measures, it can not be good. Buy yourself a control unit.

 

[Joe G.]

I have had mine for over 150K miles. No problems at all. The worse thing that has ever happened is that I managed to kill the engine once shortly after I installed it. I don't think my system is unsafe at all. I have foot button to cause an unlock instantly.

 

[Dual EE]

I use mine a lot when towing. Whenever I am desending a steep grade I will lock up my tc to help keep my speed down. I don't feel its unsafe (other then for your transmission if you leave it locked up and try to stop).



y-knot- I would be courious to know why you feel it is unsafe. Maybe I am missing something. I figure using it to save my brakes is being safety minded.

 

[dalton4]

I have about 50,000 miles with the switch. It is a manual operation and you need to stay engaged while using it. Like Joe G. , I've had no problems. The factors I like best are its cost and simplicity.

 

[Howard Durand]

Y-knot has a point about overriding a system that provides safety measures but in the case of OD and TC control, I don't think DC did a good job on the PCM for the 47RH transmission. It shifts into OD and locks up the TC at much too low speed and, when towing a load, this can be real tough on everything.

I have used the "mystery switch" for a long time and have learned some things to do and not to do with it.

It's most valuable function is to keep the TC locked up for exhaust brake application.

I also use it to keep the TC unlocked to stay out of trouble caused by early shifting.



Before I head out with the trailer next spring, my little black box will be set up to lock out OD when the truck starts and won't allow OD or TC engagement until the truck reaches the speed I set into it. After that it will operate normally.

 

[chrleb1]

My brother ran one on his truck and got a lot better fuel mileage. You are adding the same amount of fuel, but you are putting the power to the ground better. Without the switch, the TC locks up really late (45-55 mph). With the switch you can choose when you want the TC to lock up (basically anything over 15 mph). On lighter trucks, the lower the mph the better, but on heavier trucks probably don't lock it up under 25 or 30 mph.

 

[Slim's Ram]

where can u get one of these and 4 how much?

 

[Joe G.]

You can get the parts for just a few dollars. You need a switch and some wire and a wireing diagram.