Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Weird Brake Linkage Thing on Rear axle?

Discussion in 'The Garage' started by **DONOTDELETE**, Jul 25, 2002.

    I was looking at the K20 and there seems to be a valve up near the frame rail with a 2 bar linkage that goes to the top of the pumpkin on the rear axle.The rear brake line goes in this little valve then another one comes out of it the goes to the back axle like normal. It looks like when you hit a bump or something the linkage changes something with the valve. What is this? It's an 84 K20 that I am looking at buying. I had just never seen or heard of one of these. Thanks -80K20
     
  1. nvrenuf

    nvrenuf NONE shall pass! Premium Member

    Joined:
    Jan 7, 2002
    Posts:
    13,079
    Likes Received:
    247
    Location:
    Mobile, Al.
    It's a load sensing proportioning valve. It varies the pressure to the rear wheels depending on the suspension position (payload). More load = more brakes.
     
  2. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    That's GM's early attempt at rear wheel anti-lock brakes. It's supposed to help keep the rear wheels from locking when the truck isn't loaded.
     
  3. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    Yeah, what HarryH3 said. When hauling heavy loads you want to have good strong brakes, the problem is when empty it would cause the wheels to lock up and the rear end to hop/skid. The get the best of both worlds (soft brakes unloaded, strong brakes loaded), they put a valve on the frame to feel the distance between it and the axle. If the distance was far, it is assumed the body is near empty and you don't need as much braking force, but if the distance was close, it is assumed the body is full and greater braking force is applied. It was an alright idea, but I have seen more in bad shape (rust/rot or damages because of location) than in good. If it looks OK, I would leave it unless all you do is haul.
     
  4. wayne

    wayne 3/4 ton status

    Joined:
    Feb 1, 2001
    Posts:
    6,178
    Likes Received:
    0
    Location:
    Carlisle, Pa
    Everybody is pretty much correct on what it is. You will find it on almost all 1 tons.
     
  5. Blazer1970

    Blazer1970 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,600
    Likes Received:
    0
    Location:
    Old Mission, MI
    This is not a GM only thing. A lot of pickup trucks have this same set-up on the rear brakes.
     
  6. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    You mean someone other than GM makes trucks? Huh! I'd never have guessed! /forums/images/icons/wink.gif There hasn't been a non-GM vehicle parked in my garage in many years... /forums/images/icons/cool.gif
     
  7. thatK30guy

    thatK30guy 1 ton status Premium Member

    Joined:
    Jan 12, 2001
    Posts:
    32,076
    Likes Received:
    55
    Location:
    .
    What the others said....../forums/images/icons/wink.gif

    My three K30's all have that setup. I believe the first year for that type of brake setup was started in '81.

    Never saw this stuff on the older K30's though.
     
  8. Can you easily by pass this thing? Thanks
     
  9. thatK30guy

    thatK30guy 1 ton status Premium Member

    Joined:
    Jan 12, 2001
    Posts:
    32,076
    Likes Received:
    55
    Location:
    .
    Yes, you can. /forums/images/icons/wink.gif

    You can either remove that long bar-piece thingie that sits vertical....

    ....or unhook one of the brakelines on the top of the sensor-thingie up in the frame rail.

    I had an '84 K30 that had the hard line disconnected at the sensor-thingie at the frame rail. The long bar was still on it but I removed it because I added another 4" lift to the rear.

    Disconnecting this type of brake set up won't affect the trucks braking performance at all.
     

Share This Page