HELP Brake switch wiring- 4L80E TCC

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motorheadmike

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Nov 18, 2009
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And this is why I used factory harnesses... my eyes are bugging out of my head looking at this!
 
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motorheadmike

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Nov 18, 2009
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I get it Mike. I tend to overcomplicate things by accident, realize it, go ah shizzle, then go the easy way, rinse and repeat.

You are not alone - remember my Monte has been in wiring purgatory for months! MONTHS! And I am still not done yet.
 

fleming442

Captain Tenneal
Dec 26, 2013
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You are not alone - remember my Monte has been in wiring purgatory for months! MONTHS! And I am still not done yet.
Don't let it go too long; you'll forget what you were doing! Hopefully, you were making good notes.
 
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motorheadmike

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Nov 18, 2009
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Don't let it go too long; you'll forget what you were doing! Hopefully, you were making good notes.

Yes, notes.... good notes... I made those - yeah...
 
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Adis

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Jun 25, 2020
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I realize that this is an older thread. And that I’m not asking a G body question, but my question relates to the 4L80 brake switch that features prominently in this thread. I’ve got a ‘72 A body cutlass that I’m putting a 2004R into, with the lock up. Id like to run a brake cutoff to the lockup, in addition to the 4th gear switch. The vehicle also has factory cruise (all analog), which also has a brake cutoff. Obviously, the factory brake switch only has one normally ‘on’ connection for the cruise, since the original trans was a plain TH350 with no OD or lockup. I’ve thought about just splicing the TCC shutoff into the cruise harness at the brake switch, but the problem is that the cruise has an on/off switch upstream of the brake switch. So, if I splice then TCC into the cruise harness it will essentially be like having to switch on the TCC when I want to use the lockup function - which I’d rather not have to do (I also would like to avoid cutting the factory cruise harness.) So, what I’m wondering is, would the 4L80 brake switch solve my problem, since it has two in/out leads controlled by the normally ‘on’ part of the switch? I could send two separate 12v keyed power circuits through the brake switch, one straight from the fuse bloc for the TCC and the other coming from the cruise on/off switch on the dash. If so, does anyone know if the threads on the 4L80 switch will work on my existing bracket? Also, any chance anyone knows replacement parts numbers for the two connectors that plug into the switch?
Sorry for the off-topic question, but I appreciate any opinions, and hopefully someone can help me out. Thanks - Mark
 

GroceryGetter83

LS Mafia
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Sep 18, 2018
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Looking to use this fbody pedal switch for my two step. Which of the 4 additional pins should I hook up to get the signal for the two step? I can set as ground or +12v In the Holley.
 
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64nailhead

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Dec 1, 2014
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I used the brake light switch power wire via splicing. Used that as the signal for pin 85 of a relay. Pin 86 ties into a switch that had the other side go to ground. Then use pin 30 and 87 as grounds. Safer that way, you can never over amp/volt your ECU i you supply it with a ground.

To confuse it a little more, I tied the sloppy trans brake into the ground side of the 2 step switch via a relay to so that the 2 step won't work unless the trans brake is activated. But when I let go of the trans brake the 2 step is deactivated whether my foot is on the brake or not - which was what I was after.

Don't overthink it and use a relay to trigger your inputs - safety first.
 
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