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Anyone heard of brake proportioning valve problem with lift kits?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by shum1, Nov 20, 2000.

  1. shum1

    shum1 1/2 ton status

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    I just read a post on off-road.com about problems lifting a 1984 suburban. I guess rancho says not to lift this vehicle because it causes the rear brake proportioning valve to not send brake power to the rear. Is this problem unique to 1984 burbans? I thought burbans and blazers used the same systems and I've seen plenty of lifted blazers as well as burbans.
     
  2. 76chevy

    76chevy 1/2 ton status

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    I don't see how that is possible. I'm not familure with your set up, but on my rig all the hard brake lines don't get moved or changed. You just change the flexible brake lines, two front one rear. Maybe they didn't bleed the system right or something.

    If it is true that you can't use the vavle of an 84 go buy one for an 85 and change it.

    <font color=red>Spirit of 76</font color=red>
     
  3. blazen91

    blazen91 1/2 ton status

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    If your refering to the valve on the rear end, why not just disconnect it or even remove it? I really don't know, I'm just guessing. However I would like to know for when I lift my 86 Burben, which has that same valve.

    blazen91
    Protect the land FOR the people
    <font color=red>Not FROM the people</font color=red>
     
  4. Chris Demartini

    Chris Demartini 1/2 ton status

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    <font color=blue>My brakes instructor at auto school told us today that some 80s trucks had height-sensing rear brake proportioning units. Mabye lifting the truck makes this sensor think that since the truck is higher up, it has no wieght on it? All I know about height-sensing prop valves are meant to prevent brake lock-up on empty trucks. Mabye your Burb has one?</font color=blue>
     
  5. tom

    tom 1/2 ton status

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    biggrey71 is on the right track. My '86 suburban (no lift) has a brake proportioning valve with a linkage to sense vehicle height and adjust the proportioning valve according to rear axel load. There is a procedure in the manual for setting up the linkage. My guess is that if you lift one of these, it would be best to re-adjuct the linkage appropriately.
     
  6. shum1

    shum1 1/2 ton status

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    Now we are getting somewhere. I wonder if 1990 burban has this feature, if so, how do you recognize it and where do you look?
     
  7. Chris Demartini

    Chris Demartini 1/2 ton status

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    <font color=blue>I have never seen one but my guess is it would be on the frame near where the flexible line that goes to the axle bolts to the frame. I think it goes down to the axle too, right?</font color=blue>
     
  8. tom

    tom 1/2 ton status

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    I don't remember the exact arrangement and the vehicle isn't with me right now. The valve is just above and in front of the differential. There is a two bar linkage that causes the valve shaft to twist as the rear springs compress with load. The adjustment involves getting a little factory washer with a tang that holds the shaft in position as you tighten the linkage with the vehicle unloaded. Then you break the tang off (or something like that). You'll have to check the manual. This all relates to an '86 3/4 ton burban. Don't know if later models are similar.
     
  9. ken

    ken 1/2 ton status

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    OK, my 88 dually has one of these, and my 90 Suburban doesn't. When I installed the 10" lift on my dually 11 years ago, I disconnected the arm for the proportioning valve, fully intending to extend the arm and re-attach it. Well, its been 11 years and its still disconnected. I have never ever had any brake problems with it, and I tow an 8500 lb. boat. I know its a load sensing valve, but I just don't seem to need it. I say disconnect it, cut the arm in half, install your lift, then reconnect it with a longer piece of flat stock bridging the gap of where you cut. That should work.

    ken
     

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