What is it?

[Cemack]

Hey this is located on my firewall and I do not know what it is. Electrical connection on one side and what looks like a vacuum connection on the other. Hasn’t been hooked up since I’ve owned the truck.

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[Vbb199]

I believe thats a vacuum operated lockup switch for a 700r4

 

[Cemack]

I believe thats a vacuum operated lockup switch for a 700r4

So is it necessary to hook this up? And would it be ported or manifold vacuum? Whoever owned the truck before me pulled out all the EGR stuff so maybe they pulled this hose out at the same time. It’s an 85 by the way

 

[SirRobyn0]

No that is not for the lockup. The vac lock up unit is over near the brake master cylinder, what you are looking at is the tip in sensor for the ESC unit. If your truck still have electronic spark control then yes that needs to be hooked up. If it has been converted to a standard HEI ignition system then no it no longer would be doing anything.

 

[Vbb199]

No that is not for the lockup. The vac lock up unit is over near the brake master cylinder, what you are looking at is the tip in sensor for the ESC unit. If your truck still have electronic spark control then yes that needs to be hooked up. If it has been converted to a standard HEI ignition system then no it no longer would be doing anything.

Yea, on second anaylsis, this is right. The lockup switch is on the opposite side of the motor

 

[Itali83]

Never mind, posted incorrect information.

Ben

 

[Vbb199]

The ESC thingy has a stepped.body on it, the lockup switch doesnt as i recall. Thats the most distinct way (for me) to tell the differences.

 

[Turbo4whl]

Okay, some confusion here. 1978 truck would not have ESC (electronic spark control). Would not have a 700R4. It could have a TH350C (Turbo-Hydramatic trans with locking converter).

So that is the Tip-in switch for the converter on the original TH350C.

 

[Vbb199]

Okay, some confusion here. 1978 truck would not have ESC (electronic spark control). Would not have a 700R4. It could have a TH350C (Turbo-Hydramatic trans with locking converter).

So that is the Tip-in switch for the converter on the original TH350C.

He said its a 1985 though, it could have both an esc, and a 700r4?
Unless i am confused by your response lol, my brain is slow these days.

 

[Turbo4whl]

He said its a 1985 though, it could have both an esc, and a 700r4?
Unless i am confused by your response lol, my brain is slow these days.

You are right, Chris's second post states 1985. I was looking at his signature that says 1978.

 

[SirRobyn0]

Yea, guys I was going to say there is no way this is his 78 350. That's a tip in switch for the ESC, no doubt about it, but if Chris wants to post any part numbers he can see on that I'll look them up in my reference book to verify.

TIP in switch is for the ESC and is located on the passenger side near the transmission dipstick on every ESC rig I've seen. As I understand primary function is for when the driver punches the throttle, the tip in switch sends a signal to the ESC module to slow the advance curve. As the petal is held to the floor the module will turn up the advance until the knock sensor detects knock and holds the timing just below that. Hence it tips the timing advance in. So if his truck still has a functioning ESC system it is important that it be hooked up. If it's been converted to conventional HEI then it doesn't perform any functions anymore.

Lockup converter vacuum switch is not the same as the tip and switch and is not the same part#, but does look similar, but is located on the driver side near the brake master cylinder.

 

[Cemack]

You are right, Chris's second post states 1985. I was looking at his signature that says 1978.

Yeah, I sold my 78 after I restored it. I have an 72, 85, and a 98 now!

 

[Cemack]

No that is not for the lockup. The vac lock up unit is over near the brake master cylinder, what you are looking at is the tip in sensor for the ESC unit. If your truck still have electronic spark control then yes that needs to be hooked up. If it has been converted to a standard HEI ignition system then no it no longer would be doing anything.

Would this have been for the ESC as well?

You must be registered for see images attach

No that is not for the lockup. The vac lock up unit is over near the brake master cylinder, what you are looking at is the tip in sensor for the ESC unit. If your truck still have electronic spark control then yes that needs to be hooked up. If it has been converted to a standard HEI ignition system then no it no longer would be doing anything.

You must be registered for see images attach

 

[SirRobyn0]

@Cemack Without going and looking at my truck I'm not 100% sure. The easiest way to tell if the ESC is still hooked up is to look at the distributor. If it is a standard HEI unit then there will be a 2 or 3 wires that come out of the distributor and connect up to the cap. If it's still the ESC distributor it'll have that plug another connector from the module that has 4 wires and runs into the cab. The more I look at that connector in your hand the more I think it is the ESC plug for the distributor I just can't remember exactly what it looks like, but it is a 4 prong flat plug.