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Old 08-03-2011, 08:31 PM
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Another 700r4 lock up switch queston

Im sure you all are tired of questons about this but couldnt really find what i was looking for in the knowledge base.Anyway i want to wire a switch to the brakes to unlock the convertor on a 87 iroc.Can anyone tell me what the wire coler is on the brake switch that i need to tie the switch into?Thanks for any help you can give me.

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Old 08-03-2011, 09:44 PM
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Not sure if your vintage of car is the same setup as mine. Mine was the orange wire..but it is a much older GM...('68).

However, you can't wire the TCC directly to the brake light..as it will be the opposite effect that you want.

You want the TCC to have NO POWER (0 volts) when you apply the brake. By hooking it up directly you will have POWER (+12v) when you apply the brakes. Thats not what you need.

There are two options.

Option #1. Replace the brake switch with one that has an "active on" position as well as an "active off" connection. Your original brake connector will be on the "active on" and the two new terminals can be used to interrupt power going to the TCC. Of course you must run a new +12v source from a switched IGN point . This is what I have done. I can send you a diagram if you want. It is a very common switch, easy to find and cheap.

Option #2. You can tap into the existing wire on your brake switch (I believe it is the orange one). But you must use a relay to operate the TCC. This is more complex set up but works equally well. I can send you a diagram fro this as well.

Hope this helps.

Vic
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Old 08-03-2011, 10:32 PM
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Thanks for the reply.Mine locks up way to soon for me for driving around in town and stuff so what im trying to do is put a switch in so i can turn it off were it dont lock up and back on so it works normal on the highway.I was thinking that since when you touch the breaks it unlocks i could just put a toggle switch in to do the same thing as the break paddle.Basically to fool it to think the brake paddle is pushed so it wont lock up alot easier than driving around with my foot on the brake haa,but what your saying is that i cant do that?
And yea a diagram would be great.Either one would be good.Once again THANKS alot for the info.
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Old 08-03-2011, 10:43 PM
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AH..I see.

In that case it is much simpler. Don't even bother involving the brake circuit. Simply install a toggle (on/off) switch on the wire that goes to the transmission... the wire on the "A" connector...(you may only have the one wire anyway).

So cut the wire that goes to the "A" terminal of the connector. install the switch with the appropriate length of wire to be able to put it under you dash...and that's it. When in town turn the switch off. This won't permit any signal to get to the TCC..and keeps it unlocked. On the highway, put the switch back on and it will operate as normal...allowing the appropriate signal to go into the TCC as it always has. Done.


But don't forget to put it back when you're on the highway. Otherwise you will definitely be revving higher, wasting gas and generating heat in your transmission...and you want to avoid that.

Vic


Vic

Last edited by cadmanof50s; 08-03-2011 at 10:59 PM.
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Old 08-03-2011, 11:02 PM
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Sounds simple enough.Is there a way to do it off the brake switch though.I was hoping not to have to crawl in under the car and try to find a place to run the wire back up to the inside.Does the wire come to the inside any were that i could tie into inside the car.Once again thanks alot.
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Old 08-03-2011, 11:13 PM
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I'm not sure what provisions GM used for brake TCC cancellation in your car. Not even sure if they used a physical connection or a computer-based signal. In 1987, chances are, there will be a wire that connects to the brake switch to cancel the TCC that you can feed from, or bypass. That is dangerous if you don't have intimate knowledge of how it works. You could blow a fuse, burn up a circuit...or worst if you have a computer based system like a BCM..(don't even want to think about that!).

I can tell you that in the long run it will be easier to use the simple method I mentioned earlier. Everything else will require intimate knowledge of your specific year of car. (Sorry can't help you there).

Vic
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Old 08-04-2011, 08:09 AM
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Quote:
Originally Posted by chevellenut
Im sure you all are tired of questons about this but couldnt really find what i was looking for in the knowledge base.Anyway i want to wire a switch to the brakes to unlock the convertor on a 87 iroc.Can anyone tell me what the wire coler is on the brake switch that i need to tie the switch into?Thanks for any help you can give me.
what changes if any have been done to the car? this car from the factory came with a 700 (if it came with an auto trans), and it should already have the proper pieces in place for proper lockup operation.
have you checked the brake switch to verify that its just a 2 prong brake switch and not a 4 prong? from the factory, this car came with the means for t.c.c. to be cancelled when hitting the brakes.
what gear is the t.c.c. coming on? are you sure that you have no electrical or mechanical issues that are causing a malfunction of the t.c.c. system?
more info would be great in helping you find the problem and correctly fixing it.
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Old 08-04-2011, 05:54 PM
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As far as i know everything is stock on the car.Havent had it to long,just rebuilt the moter just back stock 305.I thought i was up shifting to quick but its not,Ive set and set the tv and it shifts good.The probley comes in when your going through town or up a hill say at 5 to ten mile hour when you first touch the gas it wants to lockup,give it a little more gas and it kicks on down and does good or just touch the brake and it unlocks and does fine.Dont know what the real issue is but i figure if i just put it on a switch and leave it off untill im on the highway,cheap,and should be simple.
The brake has two switchs on it.One has a vacum line to it,dont know if that goes to trans or cruise control but i couldnt find any wire that when the brake padel was pressed that the current was lost.So i quess im going to go the way the other guy suggested.Sound like the best any ways.
How do i know which is the A terminal on the harness.Are they marked on the plug or some where,Havnt been under it to see how many wires are going into the tranny.Thanks alot everyone.
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Old 08-04-2011, 10:06 PM
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The plastic four pin connector is on the driver side of the transmission. The "A" terminal on the 4 pin connector is the wire farthest to the left and farthest to the front.

I wanted to add one comment: My understanding is that you don't want to have lockup while driving in town. What about just shifting into 3rd while in town. This is exactly what I do and what a lot of folks with these tranny's do. By staying in third, you will reduce the amount of torque slippage and lockup won't occur...(unless you have one that does lock up in 3rd). You get better throttle response, you don't have to do a forced downshift and all you have to do is just move the stick shift..no wiring no cutting...??

Good luck,
Vic

Last edited by cadmanof50s; 08-04-2011 at 10:13 PM.
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Old 08-04-2011, 11:10 PM
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Yea it locks up in third to.Something just dont seem right with it,it hold first kinda late and shifts pretty firm which is fine but under light accelaration it goes to second then pretty much into drive it seems to do this worse after it is warmed up.If i just get this convertor from locking then i can tell alot more on what its doing for sure.Shifts great under normal accelaration.
If i understand it right if im standing facing the drivers door the A connection is bottom left hand wire.Is this correct?Thanks for the input guys
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Old 08-05-2011, 04:38 AM
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On a 700r4 the 4-pin connector receptacle actually faces up. i.e the connector that you plug into it faces down...and it only goes in one way.

Therefor "A" is considered to be the receptacle pin which is farthest to the front of the car and most outboard (farthest from the transmission casing):

The red wire this picture is in the "A" terminal:

http://www.700r4.com/tech/tcc/relay_...nnector_bg.jpg
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Old 08-05-2011, 02:49 PM
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Wanted to think everyone for the info,crawed up in under it to day and wired the switch into the A termianal.Works great seems to have took care of the problem,when im in town or back roads i just turn it off and when on the highway flip it back on and locks right up.Know the bad part is when i was coming back home the car quit,pulled over and started right back up.Drove it a couple more miles and same thing like its running out of gas but this time it didnt die,after a few seconds of giving it gas and letting off it straightend up but that was only about a mile from the house.Haaa got to love old cars,alwayyyys something needs fixed on them.Any ways it got a new fuel pump and filter do if any one has any ideals on that chime in.If i dont figure it out ill probley post it in the approperate section.Anyways just really wanted to say thanks to all,ive always found this site very helpfull with very knowledgeable people on it.
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Old 08-05-2011, 11:17 PM
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Glad it worked out for you. Now, on to your next problem...
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