GMC Truck Rear Brakes

[33ppp]

I am in the process of fixing up a 1986 GMC K2500. I am running new brake lines and noticed that there is a leveling device over the rear axle that once was connected to the brake lines. Someone previously bypassed it. I don’t know the name of the part and can’t seem to locate one. How important is this load sensing mechanical device? I am putting this truck back in service to be driven. Are replacements available? I did not see it in the LMC catalog.

[Keith Seymore]

It is a 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

[33ppp]

Thanks,
I was thinking that there must be tens of thousands of theses trucks still on the road and many would'nt have that device in service any longer. This truck is more of a project truck that will be used for work in the event that one of my two other trucks is out of service.

[dieseldawg142]

i find my brakes are better without it, just yanked mine off yesterday, really cleans it up underneath too