Vacuum switch, break switch, and wiring for 700-R4

scrap--metal

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Like the title says, I'm looking for the lock up converter stuff for a 700-R4 in a K20. I need the vacuum switch, the brake switch, the relay, and the associated wiring if that's available too. My K20 has a 700-R4 and it's not plugged into anything. I'd like to try and get the lock up converter working.

A buddy across town is parting out his old plow truck because the frame cracked, but that truck had a TH400 so he doesn't have the stuff I'm looking for. Then, there was a Suburban being parted out last month about an hour away from me, but now I don't see it on C-list anymore. :confused: If only I knew I needed these parts a few weeks ago...

Anybody able to help me out?
 

scrap--metal

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So I found the guy parting out the '88 Suburban I mentioned in my previous post. The truck had an automatic (guy said either 700R4 or 4l60). I don't think they came with 4l60's, so I'm optimistic that it had a 700R4. He sent me a pic of the firewall where I though the vacuum switch should be, but it doesn't look like it's there.

Is the vacuum switch mounted someplace different on a 'burban vs. a K10 or K20?

Here's a pic of the part-out:
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Itali83

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What year was the suburban? If it was 87-91, it’s tbi and no vacuum switch.

Ben
 

78C10BigTen

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Pretty sure its on the pass side firewall...
 

scrap--metal

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What year was the suburban? If it was 87-91, it’s tbi and no vacuum switch.

Ben
It's an '88, so that explains it. Thank you for the insight.

It there a TPS to control the lock up in a TBI system? What replaces the functionality of the vacuum switch in earlier 700R4 applications?
 

scrap--metal

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Pretty sure its on the pass side firewall...
He sent me another pic with some of the passenger side firewall visible, and I didn't see it over there either. Thanks though, Ted.
 

Itali83

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It's an '88, so that explains it. Thank you for the insight.

It there a TPS to control the lock up in a TBI system? What replaces the functionality of the vacuum switch in earlier 700R4 applications?
The ecm controls lockup. Looks at throttle position, map sensor and coolant temp.

Ben
 

ballencd

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Slightly off topic but how do you tell when the lockup on a 700R4 is engaged? 1991 Suburban
 

gmbellew

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Slightly off topic but how do you tell when the lockup on a 700R4 is engaged? 1991 Suburban
I have a 1990 burb. 350tbi. 700r4. 4x4. 3.73 gears. 33in tires.

I can feel lock in in the highway in 4th. it feels almost like a subtle gear shift...drops RPM about 200 or so. also, unlock should be noticeable on slight inclines before any 4-3 shift would occur.
 

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