Anyone know what this is ?

[VAL]

On the firewall, there's a hose that's not hooked up to anything, it is taped to a harness that goes into the cab. There's a vacuum switch I think, it looks like the tranny lock-up switch which is on the opposite side of the firewall.

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[HotRodPC]

If You're talking about that thing bolted to the firewall with a vacuum port *** on it and some wires on the other side of it.... That is the Vacuum Swtich for Torque Converter Lock up. That is what the NON ECM controlled Th350C and 700r4 trucks used to lock up the converter.

 

[HotRodPC]

If you're talking about a hose that comes out of the cab and not hooked up, it probably goes to your Heat and AC Blend door, or defrost blend door vacuum diaphram controls.

 

[VAL]

Ok, but there's another vacuum switch on the driver side, to the upper left of the master cylinder(second pic), it almost looks identical to the TC lock-up switch. The hose has got me baffled, because all my a/c & defrost blend doors, everything is working just fine as it is.

 

[MrMarty51]

One of um might be for the distributor vacuum, they did`nt wantum pulling vacuum advance with a cold enjun, leavum itum by passedum.
Thatum isum Myum oldum schoolum TV Indian talkum. fromum the 60s.

 

[chengny]

Was the truck originally equipped with cruise control?

That might be a vacuum release switch - dumps the throttle control vacuum when the brakes are applied.

Wash it with some carb cleaner and see if you can find a 1407**** part number.

 

[VAL]

The truck has factory CC. I'll check it tomorrow, and let you know.