What Is This In My Frame Rail?

[Nailhead]

I have no idea what this is plumbed into the rear brake line-- Mico lock? Oddball brake light switch?

[Von]

Brake lock? Mine had the switch for the brake lock in the dash but whatever was at the other end had already been removed.

[brute4c]

If it were a brake light switch it would need an electric connection...don't see one...

A mico lock has a control lever somewhere on it...dont see that either...

a proportioning valve of some type maybe...

[Nailhead]

It's got an electrical connection, hanging down in the center of the photo, which has what looks to be an unused male connector shell plugged into it.

[Don Cavey]

It is a brake lock and as mentioned above, mico brake. I suspect your truck left the factory as an M724 as mine did. It created problems with my brakes and I removed it. For the M715, it isn't used.

My suggestion is to simply replace it with a length of the same size steel the same size as the tubing going to the rear brakes.

[kwai]

I think Don has it right. Probably a mico-lock. Does the dataplate on your truck show it as a M715 or a M724?

[Don Cavey]

BTW, my truck was missing the data plate with the VIN, but the other plates were there! There are clues that my truck was an M724. Welder data plate on the dash, speedometer cable type governor controls, patched hole in the floor where that lever was etc.

That mico brake solenoid will cause you problems. Quick removal would relieve many brake headaches, "just sayn'".

[Nailhead]

You know, I haven't looked at the data plates in so long, I'm not sure even what it is I'm working on anymore!

I do know there is a patched hole in the driver's side of the tunnel that had me wondering.

Thanks for the help, and I'll plan on removing that brake lock.

[Nailhead]

The driveshaft as it is now. Note band clamp.

[Von]

Wow. So they removed the levers and ALL the linkages then put a hose clamp on it to keep the coupling from moving around.