Torque Converter lockup switch

[CoastyAV8R]

Has anyone installed a manual torque converter lockup switch? I want one for two reasons, one is to use my exhaust brake in any gear. My transmission has been built with the intention of using an exhaust brake but doesn't lock up very well in 2 n 3rd unless you feather the accelerator to keep the torque converter engaged.

The other is to be able to lockup the torque converter when I'm driving at a speed that my torque converter doesn't lock up normally such as driving down a gravel road pulling our travel trailer to avoid getting the transmission too hot.

Thoughts?

 

[Ozymandias]

I did that mod a month ago, it's called a Mystery Switch. It's easy to do - but please read into it before you use it, you can destroy the transmission in a single use if done wrong.

 

[bigceltic]

I did that mod a month ago, it's called a Mystery Switch. It's easy to do - but please read into it before you use it, you can destroy the transmission in a single use if done wrong.

Can you elaborate some more, please? I have been looking at this mystery switch as well.

 

[BigPapa]

I'd like to know how it can "destroy the transmission in a single use if done wrong", as well. Haven't heard that one before.

 

[CoastyAV8R]

My wife has a Mystery Switch as well, caution must be used when using that switch also. I'll look into it, any good website/info on how to hook it up? I've watched a few videos that point you to tapping into the wiring harness where it comes out of the transmission, is that where you did it? This is a good tutorial https://www.cumminsforum.com/threads/converter-lock-up.13276/ Talks about the does n' don'ts and cautions and has pics.

 

[Ozymandias]

I'd like to know how it can "destroy the transmission in a single use if done wrong", as well. Haven't heard that one before.

Lock to Lock shift in lower gears snaps the input shaft of the transmission.

 

[Ozymandias]

Can you elaborate some more, please? I have been looking at this mystery switch as well.

I tapped it into the Lockup wire right above the ECM, it's a better place from my view then down at the transmission in all the dirt there.

It's really simple as the Lockyp is switched on by grounding that wire.

You need to put a 33 Ohm resistor in line to it so it doesn't activate the CEL.
0.5watt resistor is enough, I used 1watt as that was available fast through Amazon.

That's all.

If I'm using it I always limit the transmission to the designated gear so it won't do a locked upshift. Also I try to align the rpms before switching it on, means get off the throttle, switch, let it lock, then reapply throttle.

It will NOT downshift if it is locked with the switch, you can press the engine down till it stalls.

That's it more or less.

 

[AEdelheit]

I have seen about 5 output shafts break when people were manually locking up the converter during off road use, while it likely wont be an issue for most it can lead to alot of shock load going through the transmission when the TC would normally be unlocked.

 

[bigceltic]

My use case would be towing down a CO mountain pass, in 2nd (manually via gear selector). I have found I my TC sometimes unlocks when going down a pass and I have to start using the brakes.

 

[BigPapa]

Ozy, I totally understand that. I would hope that most with a bit of common sense wouldn't attempt that scenario.

I, too, used the wire above the PCM. I actually cut mine and wired an old school floor dimmer switch to lock it. My 12-valve/'98.5 conversion meant I had to retro the 24-valve APPS onto my P-pump. Lockup never worked properly.

I wouldn't recommend it with a stock transmission, but in my hot-rod days (big injectors, big turbo), I've locked it in 3rd under hard acceleration and let it shift to OD with no issues (I have a Goerend triple, billet input, billet band anchor, and reinforced flex plate ) and I've locked it after the shift into OD while accelerating hard enough on an on-ramp to spin the rears and drift a bit.

Ozy's correct, it will not downshift if locked. The only issues I've experienced with my switch is forgetting to unlock it. I've tried to figure out some sort of LED to indicate it's locked, but haven't figured it out yet. The first time my wife drove it with the switch, she accidently stepped on it. The car in front of her was turning left and waiting on an oncoming car. When she came to a stop it died and she couldn't restart it. I now have a piece of 2x4 with a hole in it she puts over it when she drives it.

I believe I'm correct in stating that lockup in 1st or 2nd requires VB mods. I have locked mine in 1st once and a few times in 2nd while towing heavy up a slow winding hill.

 

[Ozymandias]

Ozy, I totally understand that. I would hope that most with a bit of common sense wouldn't attempt that scenario.

I, too, used the wire above the PCM. I actually cut mine and wired an old school floor dimmer switch to lock it. My 12-valve/'98.5 conversion meant I had to retro the 24-valve APPS onto my P-pump. Lockup never worked properly.

I wouldn't recommend it with a stock transmission, but in my hot-rod days (big injectors, big turbo), I've locked it in 3rd under hard acceleration and let it shift to OD with no issues (I have a Goerend triple, billet input, billet band anchor, and reinforced flex plate ) and I've locked it after the shift into OD while accelerating hard enough on an on-ramp to spin the rears and drift a bit.

Ozy's correct, it will not downshift if locked. The only issues I've experienced with my switch is forgetting to unlock it. I've tried to figure out some sort of LED to indicate it's locked, but haven't figured it out yet. The first time my wife drove it with the switch, she accidently stepped on it. The car in front of her was turning left and waiting on an oncoming car. When she came to a stop it died and she couldn't restart it. I now have a piece of 2x4 with a hole in it she puts over it when she drives it.

I believe I'm correct in stating that lockup in 1st or 2nd requires VB mods. I have locked mine in 1st once and a few times in 2nd while towing heavy up a slow winding hill.

It's not a big deal for a light, you need a diode in the line between transmission and your switch so it isn't back feed when the converter is locked from the PCM.

 

[Ozymandias]

My use case would be towing down a CO mountain pass, in 2nd (manually via gear selector). I have found I my TC sometimes unlocks when going down a pass and I have to start using the brakes.

That's exactly what I use mine for, keep it locked on winding downgrades were speed falls in corners below the threshold of the ECM.

 

[BigPapa]

I've tried that, don't work. Do you have one on yours?

 

[bigceltic]

That's exactly what I use mine for, keep it locked on winding downgrades were speed falls in corners below the threshold of the ECM.

Thanks. And given it won't downshift, when I get to the bottom, I can unlock and upshift and not worry. I have been eyeing the BD Trans just for this reason (manual gear choice and on-demand locking) when I eventually need a new transmission but if the mystery switch works out, I will have the main functionality I need.

Now I have a project once I finish my Spring Honeydo list!

 

[Ozymandias]

I've tried that, don't work. Do you have one on yours?

No I didn't yet, but it's weird that this didn't work with the diode. Do you have an idea why?

 

[BigPapa]

Do you have an idea why?

No, I couldn’t figure it out. I have a short wire from the switch to the floorboard for my ground and a wire from the switch to the wire above the PCM. I tried an LED between the switch and the wire to the PCM and it didn’t work, reversed the polarity thinking I had it backwards and it still wouldn’t work.

 

[Ozymandias]

No, I couldn’t figure it out. I have a short wire from the switch to the floorboard for my ground and a wire from the switch to the wire above the PCM. I tried an LED between the switch and the wire to the PCM and it didn’t work, reversed the polarity thinking I had it backwards and it still wouldn’t work.

Where does the positive come from in that setup?

I ask because I've already an LED that indicates lockup (for many years now) and that works like a charm. It only does not make a difference between automatic lockdown or done by the switch. I've taken the positive Lead from the cigar lighter.

 

[BigPapa]

The solenoid has 12 volts to it and the PCM or a manual switch supplies the ground.

How is your LED wired? I’m not concerned with the auto or manual part, I just want to know when it’s locked.

 

[Ozymandias]

I just have the LED between the wire that feeds the ground to the solenoid and the positive from the cig lighter.
So when the ECM grounds that wire (or the switch now) the LED lits up. You need that separate positive to the LED to wake it work.
And there would be my place to put the diode in.

Because my switch has an integrated LED and so I'd know if the Converter is locked manually (LED in switch) or from the ECM (stand alone LED).

 

[BigPapa]

So run from a keyed 12-volt source to the LED, then to the wire going from the transmission to my switch, correct?