Lock Up Converter Vacuum Switch FAIL???

[HotRodPC]

So all along I've been told and have thought this firewall mounted vacuum switch is for TCC (Torque Converter Clutch) lock up. So I see a post the other day and someone asking what this is. 100 people all said TCC Vac Switch for Lock Up, including myself. Some guy comes in and says it's a Tip In switch to delay timing advance on ESC controlled LE9 305 engines and 1 other that I don't recall the RPO code for.

I confirmed it IS a Tip In switch for ESC (Electronic Spark Control) vehicles.

So now that the big FAIL has been pointed out, I need to find wiring diagrams to figure out where LU comes from. I've always just plugged the wires in and it worked, and I've also seen the aftermarket switches that look very similar for LU control and have added a couple for retrofit conversions in the past on other cars and such.

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[foamypirate]

The lockup vacuum switch is usually by the brake booster. Do you have one there?

 

[HotRodPC]

I haven't looked yet. I do have an idea what it looks like now after confirming the Tip in switch. It's much smaller than that Tip In switch. If it's what I'm thinking it is.

 

[350runner]

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just took mine apart... dropped the pan, solenoid and all b4 bypassing the vac switch...

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[HotRodPC]

Yep, that's the one. I do have one on the firewall near the Vac Booster, and it's wired too. The vac line is trash but all the wiring appears to be there thankfully.

 

[350runner]

I remember mine having a steal hose between the manifold and solenoid... I trashed it, but GM knew what they were doing...

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[HotRodPC]

I remember mine having a steal hose between the manifold and solenoid... I trashed it, but GM knee what they were doing...

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I think you're thinking of a vacuum modulator buddy. Like to a Th350 or Th400. We're talking about a switch that goes to the Lock up Torque Converter and has electric wires that go to the driver side of the case to the lock up switch in the trans.

 

[HotRodPC]

If I can ever find my damn media reader, I have a pic of the ACTUAL switch that's on my K1500.

I want to get accurate pics. I of all people should have known this and feel like a real dick tard for passing bad info for so long. I was told that was it, and the wires always worked at the trans when I plugged them in, so had no reason to even think different. Never thought to match up the color of wires before. But, we'll get it right with pics and diagrams.

 

[350runner]

Well I tore apart a 80k truck and it had a steal hose going to the trans lock up vac switch, so idk looked factory.

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[HotRodPC]

Well I tore apart a 80k truck and it had a steal hose going to the trans lock up vac switch, so idk looked factory.

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There is a steel hose that runs from the intake manifold, to the vacuum modulator, usually bell shaped on the passenger side of the trans. The Switch is on the firewall with a rubber hose to the intake and then wires go from the switch to the driver side of the trans. I guess it's possible that OEM could have been a steel hose, but mine isn't and it's so rotted, it does look original.

 

[350runner]

Yup if I had saved it I prob woulda dropped the cross member and pan.

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[VAL]

How the f*&k did I miss this thread! I've been tinkering around with the tcc lock up wiring on my truck for over a month now trying to troubleshoot it. Oh well, Thanks for the correction HR. A while back I started a thread on the tcc vacuum switch, I ran a line to it from the manifold vacuum on my eddy to the tip in switch. I've been driving around waiting for lock up to kick in, and nothing. Been underneath my truck a few dozen times following wires(never thought of checking the colors). HR, is it possible to have the factory setup to get to work again? I do have the vacuum switch right over the booster also, its still has wires going to it, but it kinda looks like it melted at the connector a little. Why would have this occurred? How can I test the current set up? I'm thinking I'm gonna need a new vac switch.

 

[Boone83K10]

Val, just run a manifold vacuum line to it and see if it works. You cannot buy a GM tcc switch anymore. There isn't that much to fail on these. You can get one in a junk yard or buy the TCI aftermarket which comes with a new vacuum switch.

 

[chengny]

I don't know if this is the same type of TCC system as is discussed above but it may help someone.

From what I can see here and elsewhere, there doesn't seem to be a vacuum switch involved in the TCC control circuitry. The following is from the 1987 Service Manual and indicates that vehicle speed is obtained from an electronic sensor. It may be that the speed signal in earlier years was somehow derived from manifold vacuum via a vacuum switch.

Activation of the torque converter clutch occurs when the conditions are met as shown below:

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More detailed information:

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[foamypirate]

Yep, 87' and up TCC was controlled by the ECM. Prior to that, they used the vacuum switch to sense load on the engine (vacuum signal) and control the lockup.