Can anyone tell me what this is??
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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.
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Okay, you convinced me. These should fit a Square.
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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.
AuroraGirl
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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)
Sgt Gus
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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?
AuroraGirl
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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
SquareRoot
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I got an idea....
Bennyt
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I might be wrong but don't think the second bulletin that Aurora posted has anything to do with Trailer Brake Controllers and is referring to an aftermarket part that was sold in the early to mid 90's.
A few companies in the 90's manufactured a mechanical ABS. I don't remember much about them but I think NASCAR tried them for a season. They were the size of a small can and it pulsed the brakes. There were no wheel sensors, etc. Just a round chunk of aluminum plumbed inline. While they somewhat helped with rear wheel skid; As mentioned in the bulletin, they actually increased stopping distance.
They were around $300 or so and never heard about them again after about '97. I had an old SSBC catalog that they were in but can't find it.
A few companies in the 90's manufactured a mechanical ABS. I don't remember much about them but I think NASCAR tried them for a season. They were the size of a small can and it pulsed the brakes. There were no wheel sensors, etc. Just a round chunk of aluminum plumbed inline. While they somewhat helped with rear wheel skid; As mentioned in the bulletin, they actually increased stopping distance.
They were around $300 or so and never heard about them again after about '97. I had an old SSBC catalog that they were in but can't find it.
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RanchWelder
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It is confusing because the warning sounds scary.
I can see a guy reading that on a Monday and not realizing what's implied and getting it wrong for years.
We should not be so hard on people who make mistakes here.
AuroraGirl does an excellent job of showing what she knows is correct, yet the document can be mis-interpreted into sounding like it's also saying not to do it?
Here's an idea...
Let's all go to Yale and learn fluid dynamics?
It's an hour of your life. Why not do a refresher?
You can spend an hour doing a lot worse things than learning fluid's under pressure.
Before the internet online courses, this class cost $120K.
I had to learn it for helicopter flight school back when it came in books. Then someone stole my books.
The horror.
Turbo4whl, May I please have the fuel Relay and the brake light switch?
Can use them both actually.
Your prize timing is near perfect (or within a few degrees anyways).
I can see a guy reading that on a Monday and not realizing what's implied and getting it wrong for years.
We should not be so hard on people who make mistakes here.
AuroraGirl does an excellent job of showing what she knows is correct, yet the document can be mis-interpreted into sounding like it's also saying not to do it?
Here's an idea...
Let's all go to Yale and learn fluid dynamics?
It's an hour of your life. Why not do a refresher?
You can spend an hour doing a lot worse things than learning fluid's under pressure.
20. Fluid Dynamics and Statics and Bernoulli's Equation
xc_hide_links_from_guests_guests_error_hide_media
Before the internet online courses, this class cost $120K.
I had to learn it for helicopter flight school back when it came in books. Then someone stole my books.
The horror.
Turbo4whl, May I please have the fuel Relay and the brake light switch?
Can use them both actually.
Your prize timing is near perfect (or within a few degrees anyways).
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