Is there a single prong Lock up switch?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Dano500

Full Access Member
Joined
Jul 4, 2023
Posts
292
Reaction score
450
Location
Houston, TX
First Name
Dan
Truck Year
1984
Truck Model
K20
Engine Size
5.7
So I finally noticed some leaking from the truck, since I have driven it a little more and found that it is leaking at the shifter seal. Upon poking around down there a little more, i have a few questions I could use some help with.
Is the single orange wire with a female connector on driver side the lock up switch?

On passenger side I see trans cooler lines and vacuum actuator before thst, but no “kick down” cable. I’d like to add it back, but I don’t see where to connect it.

I guess now I know why the Speedo isnt working as it isn’t connected, but it’s so long that it goes past transfer case, so I’m assuming it’s wrong one, but I don’t see where to connect that either. Supposed to be driver side near tail shaft?

What is the solenoid looking thing there by starter and manifold? Something to do with EGR? I'm assuming that is why it isn't connected to that little piece above it?


The last pic of of driver side of a couple of connectors that I see are not connected & I have no idea what they are for, so I would like to get them reconnected.

Thanks for your help!
Dan
 

Attachments

  • 2C4FD8F0-AC59-4D74-A500-9034CE41CE00.jpeg
    2C4FD8F0-AC59-4D74-A500-9034CE41CE00.jpeg
    214.3 KB · Views: 82
  • 899387D3-9989-4A22-896E-B525C2E6C2AF.jpeg
    899387D3-9989-4A22-896E-B525C2E6C2AF.jpeg
    187.2 KB · Views: 83
  • 00226BAE-3120-4877-A1DD-4C8FA5363ECD.jpeg
    00226BAE-3120-4877-A1DD-4C8FA5363ECD.jpeg
    193.7 KB · Views: 81
  • 92632074-FE82-4C69-B30C-B26B301C08D6.jpeg
    92632074-FE82-4C69-B30C-B26B301C08D6.jpeg
    170 KB · Views: 86
  • 784652BA-B710-4DEF-8C52-254F2069933E.jpeg
    784652BA-B710-4DEF-8C52-254F2069933E.jpeg
    138.1 KB · Views: 85
Last edited:

Goldie Driver

Full Access Member
Joined
Mar 19, 2018
Posts
4,042
Reaction score
6,634
Location
Houston, Texas
First Name
Britt
Truck Year
1980
Truck Model
GMC K1500 Suburban
Engine Size
350
The 3rd and 4th photo appears to be a EFE valve - early fuel evaporation in emissions speak. It was spring loaded open if the design is the same as my 1980 and pulled closed by a Thermal Vaccum Switch- TVS - on start up.

It let exhaust gases go thru the intake manifold to help preheat the fuel mix.

My speedo cable goes to a reducer box mounted on the transfer case , but I have a NP205 so your set up may be different.

I have TH350C transmission- turbo 350 with lockup converter- and I have a single prong switch on the drivers side , but the electrical connection is vertical.
 

Dano500

Full Access Member
Joined
Jul 4, 2023
Posts
292
Reaction score
450
Location
Houston, TX
First Name
Dan
Truck Year
1984
Truck Model
K20
Engine Size
5.7
The 3rd and 4th photo appears to be a EFE valve - early fuel evaporation in emissions speak. It was spring loaded open if the design is the same as my 1980 and pulled closed by a Thermal Vaccum Switch- TVS - on start up.

It let exhaust gases go thru the intake manifold to help preheat the fuel mix.

My speedo cable goes to a reducer box mounted on the transfer case , but I have a NP205 so your set up may be different.

I have TH350C transmission- turbo 350 with lockup converter- and I have a single prong switch on the drivers side , but the electrical connection is vertical.


I see, so it isn't needed. I mean, I didn't think it was, since it has been driving. How do I tell if the lock up switch is working? just a bolt meter, or? When I did get it on the highway it did seem like it was revving pretty high, even at just 55mph, but I guess that's normal for a three speed?

I don't know how to tell which transfer case I have, but maybe its in the same location.

Any idea on the last photo? I just wonder what those two connectors could be for.
 

Goldie Driver

Full Access Member
Joined
Mar 19, 2018
Posts
4,042
Reaction score
6,634
Location
Houston, Texas
First Name
Britt
Truck Year
1980
Truck Model
GMC K1500 Suburban
Engine Size
350
I see, so it isn't needed. I mean, I didn't think it was, since it has been driving. How do I tell if the lock up switch is working? just a bolt meter, or? When I did get it on the highway it did seem like it was revving pretty high, even at just 55mph, but I guess that's normal for a three speed?

I don't know how to tell which transfer case I have, but maybe its in the same location.

Any idea on the last photo? I just wonder what those two connectors could be for.

On Goldie, it feels and sounds kind of like I hit 4th gear around 40MPH. It is noticeable to me.

I cannot tell on the phots. Looks like you are under the driver's side looking up. Cam you see the 2 prong connector from under the hood?

I am wondering if it is maybe for the cruise module.
 

squaredeal91

Full Access Member
Joined
Mar 10, 2023
Posts
2,534
Reaction score
4,579
Location
Cave junction Oregon
First Name
Greg bush
Truck Year
1991 SB
Truck Model
K30
Engine Size
5.9 Cummins 12 valve
Curious what year this rig is? Maybe i missed something Im probably wrong but I'll ask a dumb question. Is this a th400? Looks like kickdown wire to me. Goes to gas pedal.
 

NickTransmissions

Supporting Member
Supporting Member
Joined
Aug 3, 2023
Posts
412
Reaction score
851
Location
Las Vegas
First Name
Nick
Truck Year
1987
Truck Model
R10
Engine Size
350
So I finally noticed some leaking from the truck, since I have driven it a little more and found that it is leaking at the shifter seal. Upon poking around down there a little more, i have a few questions I could use some help with.
Is the single orange wire with a female connector on driver side the lock up switch?

On passenger side I see trans cooler lines and vacuum actuator before thst, but no “kick down” cable. I’d like to add it back, but I don’t see where to connect it.

I guess now I know why the Speedo isnt working as it isn’t connected, but it’s so long that it goes past transfer case, so I’m assuming it’s wrong one, but I don’t see where to connect that either. Supposed to be driver side near tail shaft?

What is the solenoid looking thing there by starter and manifold? Something to do with EGR? I'm assuming that is why it isn't connected to that little piece above it?


The last pic of of driver side of a couple of connectors that I see are not connected & I have no idea what they are for, so I would like to get them reconnected.

Thanks for your help!
Dan
Hi Dan,

The small wire going to the transmission's case connector is for the detent solenoid. Th400s dont use a purely mechanical kick down system like the TH350; the detent system is "electro-hydraulic" in that it uses a solenoid to perform the same function as a kick down cable and corresponding valve. The th400 has a valve train in the valve body with two valves: detent and detent regulator. They work with the detent solenoid to help manage downshifts.
 

Dano500

Full Access Member
Joined
Jul 4, 2023
Posts
292
Reaction score
450
Location
Houston, TX
First Name
Dan
Truck Year
1984
Truck Model
K20
Engine Size
5.7
On Goldie, it feels and sounds kind of like I hit 4th gear around 40MPH. It is noticeable to me.

I cannot tell on the phots. Looks like you are under the driver's side looking up. Cam you see the 2 prong connector from under the hood?

I am wondering if it is maybe for the cruise module.
I see, I don't remember noticing that, but I've only driven it on highway one time.

Yes, you are correct, Looking up from Driver side to see those two different connectors just dangling there.
I couldn't find anything that I could see that it would go to as far as two prong connector and the on the blinker handle, there is no option for cruise, just the blinkers/ wipers.
Curious what year this rig is? Maybe i missed something Im probably wrong but I'll ask a dumb question. Is this a th400? Looks like kickdown wire to me. Goes to gas pedal.
Hey, Square, according to the pan, it is a TH350, but IDK. The truck is an 84'.
Hi Dan,

The small wire going to the transmission's case connector is for the detent solenoid. Th400s dont use a purely mechanical kick down system like the TH350; the detent system is "electro-hydraulic" in that it uses a solenoid to perform the same function as a kick down cable and corresponding valve. The th400 has a valve train in the valve body with two valves: detent and detent regulator. They work with the detent solenoid to help manage downshifts.
Hi, Nick, thanks for the info... I believe this is a TH350 according to the pan. On the passenger side, below the cooler ports, there is a vacuum solenoid. Is that for the kick down?
 

NickTransmissions

Supporting Member
Supporting Member
Joined
Aug 3, 2023
Posts
412
Reaction score
851
Location
Las Vegas
First Name
Nick
Truck Year
1987
Truck Model
R10
Engine Size
350
Hi, Nick, thanks for the info... I believe this is a TH350 according to the pan. On the passenger side, below the cooler ports, there is a vacuum solenoid. Is that for the kick down?
Nope, that's the vacuum modulator. Not a solenoid. Your pan looks like this?
This is a TH350 Pan.
You must be registered for see images attach

This is a TH400 Pan
You must be registered for see images attach

I'm 100% positive those pictures show a TH400.
 
Last edited:

Dano500

Full Access Member
Joined
Jul 4, 2023
Posts
292
Reaction score
450
Location
Houston, TX
First Name
Dan
Truck Year
1984
Truck Model
K20
Engine Size
5.7
@NickTransmissions, sorry I never responded, I didn’t even know you had responded. Yes, you are absolutely right. It is the bottom one, so I was confused. Lol

I have to check to see if the vacuum modulator is even connected because I don’t see it on intake behind carb.
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,693
Reaction score
6,869
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
So I finally noticed some leaking from the truck, since I have driven it a little more and found that it is leaking at the shifter seal. Upon poking around down there a little more, i have a few questions I could use some help with.
Is the single orange wire with a female connector on driver side the lock up switch?

On passenger side I see trans cooler lines and vacuum actuator before thst, but no “kick down” cable. I’d like to add it back, but I don’t see where to connect it.

I guess now I know why the Speedo isnt working as it isn’t connected, but it’s so long that it goes past transfer case, so I’m assuming it’s wrong one, but I don’t see where to connect that either. Supposed to be driver side near tail shaft?

What is the solenoid looking thing there by starter and manifold? Something to do with EGR? I'm assuming that is why it isn't connected to that little piece above it?


The last pic of of driver side of a couple of connectors that I see are not connected & I have no idea what they are for, so I would like to get them reconnected.

Thanks for your help!
Dan
that flap by the manifold is the EFE as goldiue said :)
 

Latest posts

Forum statistics

Threads
44,157
Posts
950,592
Members
36,271
Latest member
jstewart7501
Top