mystery switch

[SRehberg]

I just installed the poor man's torque converter control for use with an exhaust brake; i. e. Mystery Switch. My question is this: if you are pulling in OD, then hit a hill (trailer in tow) can the OD be shut down so you are in 3rd without having to unlock the torque converter?

 

[Joe G.]

You can do that. You should to give it some fuel so the engine increases in RPM during the shift to help with the shock. Takes a little practice to get the shift smooth. I may just unlock and stay in OD depending on RPM, EGT, and trans temp.

 

[SRehberg]

Joe, I think the suggestion about just unlocking and staying in OD is a good one, as third is a little fast (rpm) with the 4:10 gears. I need to get the trans temp guage installed (it's sitting on my work bench), but have wanted to wait until I get up to BD in British Columbia for a torque converter change. I figured I'd change the pan out at that time, which has a place for the temp probe.



Thanks for the help, I appreciate it.

 

[Bill Stockard]

Your '96 may be different, but I had a Mystery Switch on a previously owned ''97 3500 and it wouldn't shift down from 4th(OD) to 3rd (Direct)as long as the torque converter was locked. Both the engine and transmission were stock.



It also had 4. 10 gears and I did run it a lot in 3rd with the torque converter locked. No problem other than a lot of engine noise. As long as the torque converter was locked, the transmission temperature never got over 180 degrees, measured in the pan, towing a 31' Hitchhiker with 2 slideouts(21,000 lbs GCVW) all over the western US.



On long steep grades in hot weather in 2nd gear, torque converter unlocked, the transmission temp would get up around 220-230 degrees along with the engine. The engine temp would also get up because of the coolant to transmission fluid cooler on the side of the engine was "dumping" a lot of heat to the coolant. The engine temp was more of a limiting factor than the transmission temp.



Bill

 

[SRehberg]

Bill, thanks for the reply. I was reading on the TST site about the operation of the switch, and I believe one of the things it mentioned was the fact it wouldn't downshift from OD to 3rd with the switch engaged. I understand what you mean about engine noise with the 4:10 gears, that's what is in this truck. I would like to have a lockup feature, but have been cautious since this last go around; I still don't know if I'm fighting an intermittent issue or it just woke up again.



Would I experience the same issues if I installed an aftermarket electronic controller? I don't know if they just tap onto the same wire or not.



Perhaps using the switch or the controller the PCM has to be reflashed in either case. Has anyone had to do this with the electronic version?

 

[Joe G.]

When I replied above I forgot that my DTT VB will allow a shift out of OD with it locked. I'm so used to it that I forgot that the stock VB won't let you do that.

 

[SRehberg]

The valve body mods are next, but that will have to wait for awhile. It seems like it all takes $$ but if it makes it last longer, then it's worth it. Thanks Joe for letting me know yours has been modified.

 

[Bill Stockard]

When I hooked up my mystery switch, I didn't use the the diagram on the TST site. Instead, I used a double pole double throw switch(DPDT) and cut the wire to the PCM instead of tapping into it. I hooked up one side of the double pole so I could flip the switch one way to lock up the torque converter(actually all it will do is hold the torque converter in lockup after it locks up initially), flip the other way to run the factory setup, and switch to the center position to unlock the torque converter.



On the other side of the double pole switch, I hooked it up to a 12 volt power source and installed a 12 volt pilot light on the dash. I wired up the pilot light to illuminate when the torque converter was switched to lockup so I wouldn't forget to unlock it when coming to a stop. I did that once...



Bill

 

[Joe G.]

Originally posted by Bill Stockard

... . so I wouldn't forget to unlock it when coming to a stop. I did that once...

Me too. A few times. That's why I have my ground thru a button on the floor that I can step on to quick disconnect the lockup. Real bad case of CRS.

 

[SRehberg]

Good suggestion on the light or floor switch. I suffer from the same disease of CRS.



Have either of you tried one on the electronic controllers and is it hooked up like the switch but provides an electronic baby sitter for not forgetting? If that is the only advantage to the electronic one, then why not put the lamp or floor switch in to do the samething. What scares me is the issue I just went through, so I'm a little cautious of messing with it again. If all it needed was a reflash to make it work, then I could live with that. When I thought I had toasted the PCM somehow or other part, it got my attention!

 

[Joe G.]

I'm not so sure that there is an electronic controller that works on a 47RH like I have so I have no experience with one. I use the floor switch to unlock for stop signs and things like that as well as forgetting to unlock. There is a lousy picture of my switch in my Reader's Rigs gallery.

 

[Bill Stockard]

There were no electronic boxes available that I knew of when I installed my mystery switch. There was no diagram on the TST site either. I experimented using the wiring diagrams in the Service Manual. I installed the first switch without the pilot light without making the change in the power distribution panel. When I tried it, as soon as I turned on the ignition switch, there were relays clicking and nothing would work. I was afraid I had messed up the Powertrain Control Module. I finally figured out to remove the relay and put in a jumper wire.



I didn't know about DTT when I owned the '97 3500. If I had, I would have kept the truck much longer after installing a DTT upgrade and an electronic box to control the lockup of the torque converter, a TST plate, and a governor spring kit which would have made it a much different truck towing our 5th wheel. I got sick of the "sloppy" torque converter, slow lock/unlock, and shifting of the automatic and traded for a '00 3500 with a 6 speed in September of '99.



Bill

 

[SRehberg]

Today I got a reply back from SunCoast Torque Converters regarding their torque converter control. Their person seemed to think it wouldn't matter if I had the Mystery switch or their controller, my problem was not associated with it. I guess the only advantage to an electronic controller is not having to remember to disconnect the switch when slowing or shifting. For $200plus I think I'll try the switch again. I'm a slow learner.



I tried the truck on the freeway today with the 5er and tried the exhaust brake by trying to keep the torque converter locked with my foot action. What a joke that was; I might as well have thrown out a pillow with a rope attached to the bumper for all the good that did.



I can see where it has to be forceably locked to have any effect, but I sure love those 4:10 gears!