Rear brake load proportioning valve

[86M10086.2L]

I just lifted my 86 M1008 and much to my dismay, while finishing up the rear of the truck and getting ready to connect the linkage for the rear proportiong valve I watched as my brother spun the valve to "see if it was free and working" So now armed with no knowledge of where it was originally positioned. I set it where I thought it should go and put everything back together. Well, the brakes haven't been the same since. can anyone tell me how to adjust the valve so I can get my brakes back? The TM tells you to use some type of gauge to set it, buy placing the tang of the gauge in the lower valve mounting hole, then cut the tang off it. Mine doesn't have that on it, cut or not. Is there a generic way to adjust this or am I going to have to go with a trial and error approach?

 

[mangus580]

Well if you can figure out which way it was pointed......

What I did when I lifted a civvy truck that had it, was make a bracket to bolt to the rear end, that raised the valve by the amount of the lift. Therefore putting the valve in the same relative position to the body/frame.

 

[Westech]

we just take them off... set the brake shoes a little on the loose side and your good to go

 

[CCATLETT1984]

Like Rich said, rip it out. if anything you can get a cheap adjustable pressure regulator for the rear brakes. You may want to drop the pressure to the rear unless your always loaded, with an empty bed the brakes will be a bit touchy in the rear.

 

[Westech]

but with the brakes set loose its all good to go. I have taken off dozens of them in my shop life.

 

[Croatan_Kid]

I welded a 3" spaced on the "arm" of my prop valve, like they said, just putting it back the same it was before I lifted the truck. I actually ran it dropped down for a long time and never did lock up the rear brakes.

 

[FMJ]

I'll take a pic of mine in the morning, I fabbed up a 4" extension, the brakes seem the same as before the lift. I haul alot of heavy @hit in my truck and like the idea of having more rear brake bias applied as the load increases. Removing the proportioner and setting the brakes "loose" puts more strain on the front calipers, whats the sense of having HUGE rear drums if they aren't doing anything?, also, if they are working, the rear adjusters will remove the slop in the rear shoes after awhile.

 

[Recovry4x4]

Frankly, I've never experienced any kind of benefit with that crappy device. I reinstalled mine in the dumpster on my 86 K30.

 

[86M10086.2L]

well, I made brakets to compensate for the lift, the poblem is, the center section of the valve was spun so I don;t know where it was sitting originally. Putting the arm back to where it was is easy. it's knowing where the valve was set that is the problem. I just ned to know how to reset is with out the gauge the miltary uses. Or maybe if someone cal take their arm off real quick, and tell me in which general direction the flat on the shaft of the vale is pointing I can reset mine like that and be done with it.

 

[appnut1]

From the factory they did not use the adjuster so you will see no remnants of it. The only way to get the right adjustment is to get the gauge from Chevrolet (this is not a military only part) and set it as described. These critters were not used for years prior to the explosion of car people buying trucks cause they were cool, and not really knowing how to drive them. The soccer moms and the like needed help in not swapping ends in an unloaded panic stop

 

[86M10086.2L]

what are the chances the GM still even makes the gauge or carries them?

 

[AJMBLAZER]

Little as GM stopped using these things over a decade ago. As the guys on CK5 said these were kinda problematic for GM.

If you can find a good GM dealership that can actually search for obsolete part numbers and find them in dealers with NOS parts on the shelves you might have a chance.


My valve thingy is still on the truck...don't think it works though.

 

[Matt65]

 

[GM72K10]

this is it

 

[plumnjoe]

So which way is the flat side of the splines on the valve indexed? Is there anybody that can at least answer this??? I pulled mine apart to install a 8" lift and also need this information. The only thing I have figured out is that the valve has a certain resistance (like a click) when spinning it in either direction. This valve was working fine before the lift so I DON'T want to remove it!

 

[doghead]

Did you ever resolve this issue? The same topic came up today.

 

[Carpenter]

i recommend against eliminating the rear brake proportioning valve. It is designed to increase braking power to the rear wheels when a load is added to the bed. For instance, if you were to load 3000 pounds of gravel in the bed, you want the rear brakes to deploy first and strongest. As a load is added to the bed, the frame moves downward. The rod that connects the rear axle to the valve does not move downward (because it is connected to the axle), and this causes the rod to rotate the valve counter-clockwise thereby increasing the brake pressure to the rear wheels.

It's easy to fabricate a longer connecting rod. I posted details of this in post #75 of my rebuild thread. After fabricating a longer rod, before connecting it to the valve make sure the little dot on the valve is pointed straight up.

Hope this helps.

From a thread located here: http://www.steelsoldiers.com/cucv/63790-rim-tire-set-up-7.html