Torque Converter Lockup.

[kenm78]

According to my vacuum chart there is a transmission lockup converter vacuum switch. I am thinking this is supposed to lock up my converter when It needs to. Well unfortunately when I bought it I found a toggle switch and I manually have to turn the lock up on and off. Gets old after a few times. Does anyone know where this switch might be located, or have a picture of what it looks like? I would like to try to get it working so I don't have to flip the switch every time.

[gchemist]

The switch is on the driverside firewall. It's next to the fusible link. It's normally covered/behind by a plactic wire wrap. LMC has the part available.
It looks similiar to the ECM timing switch. Switch on the left side.


Opss forgot this link: http://www.73-87.com/7387garage/drivetrain/lockup.htm

[kenm78]

I just looked through the LMC online catalog I couldn't find it. Were did you see it at?

[joe231]

What year truck?

On my '80 the vacuum switch is located on the fire wall just above, and towards the passenger side a bit from the brake booster. The lock up wiring runs through the vacuum switch and also through a set of contacts in the brake switch also

[gchemist]

http://www.lmctruck.com/icatalog/cc/full.aspx?Page=136

[S10Fan]

Originally Posted by kenm78

According to my vacuum chart there is a transmission lockup converter vacuum switch. I am thinking this is supposed to lock up my converter when It needs to. Well unfortunately when I bought it I found a toggle switch and I manually have to turn the lock up on and off. Gets old after a few times. Does anyone know where this switch might be located, or have a picture of what it looks like? I would like to try to get it working so I don't have to flip the switch every time.

700R4?

I'm wondering if the PO installed a "Lock Up" kit from TCI. If so,you could re-wire the toggle switch to a switch similar to a brake light switch. The new switch would operate with your brakes. Some research would be needed to make sure.


http://www.tciauto.com/

[kenm78]

Yes mine is a 80 I found a little switch it the area to the passenger side of the brake booster near a junction block. It has a single connection on one side and a vacuum hose on the other. I'm not sure why the previous owner wired in the toggle switch instead of using the OE vacuum switch. Any way to test it and see if its working? I guess now I have to try and figure out how to hook it back up to OE??

[kenm78]

Originally Posted by gchemist

http://www.lmctruck.com/icatalog/cc/full.aspx?Page=136

I must be blind all I see is the modulators, kick down solenoid inside trans (TH400), trans control solenoid (700R4), trans spark control (TH350), and trans temp switch (700R4).. I don't see it??

[kenm78]

Originally Posted by S10Fan

700R4?

I'm wondering if the PO installed a "Lock Up" kit from TCI. If so,you could re-wire the toggle switch to a switch similar to a brake light switch. The new switch would operate with your brakes. Some research would be needed to make sure.


http://www.tciauto.com/

No I have a TH350 Tranny.

[joe231]

Originally Posted by kenm78

Yes mine is a 80 I found a little switch it the area to the passenger side of the brake booster near a junction block. It has a single connection on one side and a vacuum hose on the other. I'm not sure why the previous owner wired in the toggle switch instead of using the OE vacuum switch. Any way to test it and see if its working? I guess now I have to try and figure out how to hook it back up to OE??

do you have a mity-vac?
you can run the engine and check it with an ohm meter, at idle it should have continuity (contacts closed), rev the engine and the contacts should open. Mine, IIRC, has 2 green wires. one wire goes to the brake switch and the other goes to the transmission.
do you understand how it is supposed to work?

Originally Posted by kenm78

I must be blind all I see is the modulators, kick down solenoid inside trans (TH400), trans control solenoid (700R4), trans spark control (TH350), and trans temp switch (700R4).. I don't see it??

Originally Posted by kenm78

No I have a TH350 Tranny.

TH350C?

I have a 350C in my '80 and I just recently hooked it back up, so if you have any specific question let me know

[gchemist]

Originally Posted by kenm78

I must be blind all I see is the modulators, kick down solenoid inside trans (TH400), trans control solenoid (700R4), trans spark control (TH350), and trans temp switch (700R4).. I don't see it??

Oh, you can use the same switch as a 700R4. All it does is is lockup the converter.

[kenm78]

Originally Posted by joe231

do you have a mity-vac?
you can run the engine and check it with an ohm meter, at idle it should have continuity (contacts closed), rev the engine and the contacts should open. Mine, IIRC, has 2 green wires. one wire goes to the brake switch and the other goes to the transmission.
do you understand how it is supposed to work?







TH350C?

I have a 350C in my '80 and I just recently hooked it back up, so if you have any specific question let me know

You wouldn't have a copy of the wiring schematic? That would help me understand it better. I traced the two wires back to the cab and one of them that I am assuming connects to the brake switch is disconnected I hav not tracked down the other one yet. The schematic I have isn't corrrect. Thanks for the help.

[joe231]

there are 2 different transmissions...mine is like the first one.


http://67-72chevytrucks.com/vboard/s...ht=350c+wiring

http://67-72chevytrucks.com/vboard/s...d.php?t=216865