Can anyone tell me what this is??

Turbo4whl said:

You got the participant trophy, you need to compete with another to get the winner's Blue Ribbon. No one else replied.

Click to expand...

Everyone else are a bunch of loosers. They didn't even come for the steak knives. Lol

PrairieDrifter said:

From what I'm understanding this only saying this because of the anti loc brakes? Stopping distance is affected because the anti loc brakes won't function as designed.

I hate anti loc brakes anyways lol

Click to expand...

The first bulletin from '87 was stating that because of the rear wheel antilock brakes, the connection to the trailer brake controller must be made between the master cylinder and the ABS prop valve. It could not be after the prop valve.

Sgt Gus said:

Everyone else are a bunch of loosers. They didn't even come for the steak knives. Lol

Click to expand...

Okay, you convinced me. These should fit a Square.



Top of the picture is a 4 pin plug for a 700R4 trans. Moving across the next row, brake light switch. Then a fuel RL ?? Then older brake light switch (I'll pull this out, won't fit a Square) Last row, PVC valve, wire plug (1/2"round,2pin).

Pick two, any tools that may be visible in the picture are not part of the prize shelf.

PrairieDrifter said:

From what I'm understanding this only saying this because of the anti loc brakes? Stopping distance is affected because the anti loc brakes won't function as designed.

I hate anti loc brakes anyways lol

Click to expand...

its for the gmt400 trucks, but the point was that you MUST plumb in before the combination valve, and the volume used from the tap on the master cylinder can only use that much fluid

The master cylinders in the late square are the same as gmt400
The larger gmt400 without low drag disc brakes had the same ones too, this went till sometime in the 1990s, where they possibly started phasing out the tap (not sure, personally), but they got 4 wheel antilock and so i wont speculate on how those operate in this situation.


The biggest reason for the antilock warning about aftermarket is that whatever was coming out could be dangerous because they were relying on volume of brake fluid beyond the number for trailer brakes perhaps , or that one could use the rear brake line if you didnt have a dedicated output for trailers as long as you get it before the combination valve, i think its a bigger deal on the gmt400 because their combination valve is mounted up on the wheel housing area very very close to the master (the RWAL unit is up there too), so more likely touched (meaning important the bulletin was made)

Pretty interesting. I wonder if the OP will ask a question again? Lol It made me think about ours. Given I just worked on brakes, I didn't see any brakes line changes. Could one also be just switched and control trailer brakes through trailer harness?

Sgt Gus said:

Pretty interesting. I wonder if the OP will ask a question again? Lol It made me think about ours. Given I just worked on brakes, I didn't see any brakes line changes. Could one also be just switched and control trailer brakes through trailer harness?

Click to expand...

no reason you couldnt control the trailer brakes with a modern controller, the tap was used for a perfectly proportional trailer brake operation
@bucket described its benefits to me a long time ago in my own thread asking about the one in my truck (gpa had a different kind, but its still there and the line is too)

But the best of the electronic controllers can probably be made to perform similar or have sensors/programming to do this without having a physical hookup to the brakes

I believe there would still be a blue (modern color for a 5 or 7 way, only reason i mention the color.) wire for controlling the brakes

Trailers which use a battery for deadman switching when a failure of connection happens will use the battery charge wire circuit of a 7 way to keep that maintained so that if you breakaway your trailer brakes will apply

I got an idea....