Lock Up Converter Vacuum Switch FAIL???

[MadOgre]

At it's most basic, the only thing the TCC system requires to lock up the power train is 12VDC to the solenoid.

The solenoid is internally grounded through the transmission casing. So, if the coil is good and you supply a hot wire to it, the valve will operate.

I have looked at a lot of wiring diagrams over the past couple of days and, while there are many variations of the wiring harness into the transmission, one thing is consistent. The lead that supplies power to the TCC solenoid is always light green.

Take 12 volts from anywhere, run it through a switch and feed the solenoid coil (via the light green wire). When you want overdrive, flip the switch closed and the torque converter will lock up.

Thanks guys I really appreciate all this help. Will keep you guys posted on this.

 

[MadOgre]

Yeah - from looking at the schematic that yellow wire - the one that goes from the EGR bleed valve solenoid to the 4 prong plug (in which only 3 prongs are installed) - can be eliminated.

That wire has nothing to do with the operation of the TCC solenoid. It just uses the same harness group to enter the transmission. Once inside, it splits off from the other two wires (the ones that supply power to the TCC solenoid). There are two hydraulically operated switches in series at the end of the yellow wire. They are in the ground path - "downstream" - from where the yellow wire enters the transmission.

Apparently, when the switches are both closed, the yellow wire is grounded. That yellow wire is the negative side of the EGR bleed solenoid coil. If power is available to the positive side of the coil and both those switches are closed, the circuit is completed and the EGR bleed valve opens (or closes IDK)

So from my searching the web it seems consistent that the blue/black wire to the tranny is for towing/3rd gear lock up. ?

The blue wire comes through the brake switch and feeds power to the blue/black wire through the vacuum switch which feeds back to the 4wd relay which has a circuit to the green wire which then comes back out the firewall to the transmission.

So it seems when the vacuum switch completes the circuit there is power to both the blue/black wire to tranny and also to the 4wd relay and it is up to the relay whether there is power to the green wire to the tranny.

So questions ?

Where is the 4wd relay and how does it function ?

How does the blue wire activate the TCC in 3rd gear ?

Where does the speed sensor come in to play in all this ?

It seems to me from the schematics that the TCC would function all the time in all gears according to vacuum and the 4wd relay. So im wondering what makes this happen only in 4th gear and towing in 3rd gear ?

 

[MadOgre]

You must be registered for see images attach

This is the Schematic im referring to.

 

[MadOgre]

I looked at an 84 2wd last week and it is the same as the lower diagram where as mine is 84 4wd and it is the same as the upper diagram

 

[HotRodPC]

They are just a single prong pressure switch. What determines what they're called, is where they're are screwed in. If you screw it on the 4th gear valve, then it's going to get activated in 4th, if you screw it on the 3rd, it's going to be activated on 3rd. To the best of my knowledge, the switches are the same. And I don't recall seeing a 4-3 switch. Doesn't mean they don't exist, I just don't recall working on a model that used it.

 

[MadOgre]

So there would be a switch in 3rd and 4th ? If green is for 4th then blue/black must be for 3rd ?

 

[MadOgre]

not sure why the power goes back to the 4wd relay before being sent to the tranny through the green wire ?

 

[MadOgre]

Ok just looking at the schematic again and I guess the pressure switch opens or closes according to whether or not that gear is being used? correct ? so then in third gear there is power supplied via blue/black wire and then when transmission shifts to 4th gear power is supplied via green wire as the 3rd gear pressure switch would now be unable to complete the circuit.

 

[MadOgre]

OK so this power circuit would always be functioning according to the vacuum and brake switch's at all times, and it would be determined by the 3rd and/or 4th gear pressure switch's whether or not power was supplied to the TCC ?

 

[MadOgre]

So then, what is the purpose of the 4wd relay ?

 

[MadOgre]

I guess the speed sensor would be used for the cruise controls and not the TCC function ?

 

[gta1179]

Broken Lockup switch ?

Hello, I am new to this forum. I ran across this while trying to figure out what I had on my truck.
What I got: 1984 c10 stepside 2wd, 305, th350 all original to truck (number matching).

Does anyone have a pic of where the vacuum line connect to from the Transmission Converter Release Valve Switch, (that's what the dealer and parts store called it when I showed them the pic. Mine seems to have the tip broken. but I wanted to know where the other end connects to I took pics of the before dissassembly but now the pics are nowhere to be found. Thanks in advance.

 

[Stepperado]

If there are people reading this thread because their torque converter is notlocking up, I have one more suggestion for you.

My vacuum switch was fine. What kept my '84 from locking up the converter was a cool running engine. My thermostat was stuck open. Once I replaced it and got some temp in the engine the lock up feature worked just fine.

Turns out water temp is one of the permissions on the older trucks.

 

[chengny]

Activation of the torque converter clutch occurs when the following permissives are met:

1. Sufficient road speed

2. Engine coolant at normal operating temp

3. Steady throttle position

4. Brakes not applied

5. Transmission in at least 3rd gear

You must be registered for see images attach

 

[VAL]

A while back, after long and stressful hours of trying to figuring the TCC lockup function, I got it to work, and its been working now for almost a year. The only thing I still can't figure out, is how to delay it some after 4th gear. It currently locks up simultaneously with 4th gear. It would be nice if I could get it to lock up a bit after 4th, kinda like a 5th grear