TC unlock switch?

[Dieselnerd]

Has anyone installed a switch to prevent TC lockup while getting heavy loads up to speed? This was brought to my attention by John when he stated in one of the recent transmission discussions that his DTT controller didn't allow lockup at WOT. I wasn't aware of that feature and it is a really good idea. I'm sure that's what caused the demise of my stock converter since it always seemed to lockup before I was really rolling fast enough to need lockup while towing my fifth wheel. Also, there was a large RPM drop even though I let up on the throttle. For my use, a switch would do just fine to prevent lock up until I was up to speed. I am interested in hearing from anyone who has already done this and how it worked for them. Thanks...

 

[Joe G.]

There are two versions of the infamous mystery switch. The one most often used is wired as shown on the TST web site. The original that Russel Ward came up with is different. For that one, you cut the wire from the CPM to the lock up solenoid and use a single pole double throw with center off switch. For this you attach the lock up solenoid to the center pole, the wire from the transmission to one of the outer poles, and a ground to the other pole. When the switch connects the CPM to the lock up solenoid it is normal operation. Connected to the other pole is manual forced lockup. If the switch is in the center the lock up is disabled. That's the way I have mine. On a hard pull or pedal to the metal I put the switch in the middle. So if you don't want the mystery switch you can prevent lock up by installing a simple single pole single throw switch to disconnect the CPM from the lock up solenoid. The TST web site mystery switch wiring diagram has the information you need.

 

[Strick-9]

Yes.

I have been through a few versions of unlock switches.



My truck has enough power to get myself and my transmission in trouble. Add to that the fact that I have to move a manlift for our construction company and frequently gross over 25,000 lbs. I'm a prime candidate for transmission trouble.



I started with a simple push button switch on my dash. When it's IN the truck is factory. When it's out, no lockup. Works great. Very simple.



Let's be honest though. We all forget things and get lazy. I got tired of pushing the button. And sometimes I would drive for miles and miles and forget to push the thing back in to allow the TC to lockup. This will cause the transmission fluid to get quite hot with a heavy load and no extra coolers.



I built a little box that unlocks the TC at about 1/2 throttle. DTT sells a products called the TC Saver that does just this. You don't have to buy the whole controller from them. Now I don't have to worry about which position my button is in or risk getting my transmission fluid too hot and shortening its life.



My box has a special added feature that activates a propane solenoid also. This way, my propane will never come on and cause damage to my TC clutch.



Piers stated a few months ago that one can also use pressure activated switch that opens at 20psi. You plumb it into your intake manifold and it serves the same function.



There are many ways to attack this problem. Each has it's own advantages and disadvantages just like every other thing in life. Choose what works for you and ENJOY it.



-Chris

 

[Archive]

I installed a DTT TC Saver on my truck a week ago and it is a very nicely engineered device. It is fully user adjustable and has two LED lights to let you know the throttle disengagement point is and when the TC clutch is locked up. This is one upgrade I would do again.

 

[Dieselnerd]

Thanks to all of you for some very good information. I will definitely be installing some kind of unlocking device. I appreciate the detailed descriptions from Joe and Chris. Great ideas!

 

[danandamy]

unlock switch

Just installed mine last weekend. It's an easy job. I just went with a simple toggle next to the o/d off switch. Instead of fighting finding the right wire at the pcm, I just found the wire where it goes into the transmission (orange with a black stripe, I believe). Alot fewer wires to sort through that way (thanks for the tip on that Stefan ). Other than the initial test to make sure I had the right wire and all, I won't be using mine until I get my DTT stuff in (one week, two days and counting... ).