Dually Rear End Question

[cfurlan]

After working on my brakes today, I seen something for the first time. It's and 86 C30 Crew Cab. There is a bar that is mounted to the rear axle towards the passenger side that extends up to the frame. The mount on the frame swivels, I'm assuming when the axle goes up and down. I know it has the sway bar, but does anyone know what this other thing is?

Thanks

[wyattglock]

Got any pictures? Does it have brake lines running in and out of it? If so, that is the rear proportioning valve. It gives you more rear brake bias as weight is put in the bed or on the bumper.

[cfurlan]

Looks like at one time it had lines ran to it. Is it worth putting it back in working condition?

[wyattglock]

It might be. The biggest question there is, why was it unplumbed? Unfortunately, hooking it up is the only way to find out. I don't know of anyone that sells them, but maybe someone else will jump in and help me out with that. If you are going to haul or tow a lot, it would be worth giving it a shot. If you are just driving it with the occasional load, might not be worth it.
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[Keith Seymore]

Originally Posted by wyattglock

If you are going to haul or tow a lot, it would be worth giving it a shot. If you are just driving it with the occasional load, might not be worth it.
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Other way around -

It sounds like the height sensing proportioning valve.

It was put there as "test beater" to pass the stopping distance portion of the federally mandated MVSS105 and MVSS208 brake tests. At curb, when there is less weight, the rear end sticks up and the brake line pressure is limited to the rear brakes, preventing lockup and skidding.

When weight is added, the rear end goes down, tripping the valve open and allowing full pressure to the rear brakes (and additional stopping power).

It's how we did it in the days before ABS braking.

You would probably be fine without it.

K

[meatwagon83]

mine has one on it (not like im contributing, just sayin)

[AntiGov]

I think im going to ditch mine when i swap the axle....

[cfurlan]

Hey I appreciate all the comments and information from all of you. I ended up leaving it unhooked, a new one was around $400 and I don't think I'd benefit from it anyways.

[KQQL IT]

Did a 1/2 axle swap under a R3500 and bypassed the valve. Truck drives stops great.
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[wiskers]

I have a K30 CC, had a 14 bolt and swap a dana 70, took it off and threw it away. It works great without it.
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