Can someone tell me what this thing is?

[vortec]

it's on the firewall of my 82 k5 behind the brake booster. it has a barb for a vacuum hose and on the other side it has a wire harness. the wires disappear into a wad of wire tubes and electrical tape so tracing them is not my first choice.

thanks in advance.

 

[dyeager535]

I'm gonna let someone else answer definitively, there were two used, one on passenger and one on driver side, depending on application I suppose.

I'm guessing TCC for a 700R4/TH350C?

 

[vortec]

of course! i'm getting so rusty with the old stuff since i've been working on my friends' new vehicles lately . they have more plastic and wires than steel. thanks for jogging my memory.

 

[Backroads]

yeah, looks like TCC on my 350C.

 

[pauly383]

yeah, looks like TCC on my 350C.

Bingo ! That lets the tranny know when your cruising steady via engine vacuum

 

[us74k5]

I do believe I copyrighted the red paint shop "wtf" on photo's. Please ask permission to use that in the future. Thanks

 

[ciffer]

what happens if no vacuum line is attached?

 

[mattman4x4]

then your flux capacitor explodes and the transmission dose not work.. just kidding, no idea

 

[Blue85]

If that vacuum switch is not connected, you will only get TCC lockup in 4th gear. With it connected, you will get lockup when your vacuum is high enough and TV pressure is low enough. There were a lot of different setups over the years, but that's the jist of it.

Look at the vacuum diagram under the hood. It should tell you what to connect that to.

 

[Backroads]

what happens if no vacuum line is attached?

not much... the converter wont lock up anymore. I'm not even sure if mine works. I was thinking of hooking it to a switch



I dont have my electrical diagrams here, (or my trucks) cuz I'm in the process of moving... I'll also say that it was only about two years ago that i found out there are turbo 350s with a lock up converter.


I could be off here, I aint no trans guy, but if I remember correctly-


a wire goes to the brake pedal, when the ignition is on power goes to the wire

if your foot is off the pedal the electricity flows through

the wire then goes to the vac switch (green wire?)

at the proper vacuum, the switch closes and sends the electricity to another (green?) wire that goes down to the trans

that wire goes to a solonoid on the trans, and if the trans is mechanicly "ready" (meaning in third gear and your speed high enough) the converter will lock (lowering your cruising rpms a little)


btw if you step on the brake pedal, you open the circuit, causing the converter to unlock

 

[Blue85]

Most of them have 2 "hot" wires to the tranny. 1 is interrupted only by the brake switch. This means the only things that prevent lockup in 4th are either brakes applied or transmission is shifting. The 2nd is the one going through this vacuum switch and it generally also goes through a relay, interrupting the circuit when the t-case is in 4WD. So this 2nd circuit is for 3rd (and sometimes 2nd) gear lock-up.

If in fact a 700 had "no lock up" it would probably die, unless you never used 4th gear. They cool for crap in 4th gear.