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RPO codes and Brake parts?

Discussion in 'The Garage' started by Fubeca, Jan 9, 2006.

  1. Fubeca

    Fubeca 1/2 ton status

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    Okay - so I started tearing into the rear brakes to see what the problem is on my new truck. It is a 1984 c20 with a diesel motor. The RPO sheet is missing but the door tag says it has a GVWR of 6400lbs. It has a 14B SF and 11-5/32" by 2-3/4" brakes.

    When I went to the store they listed JD6 or JD7 as the brake options, since I've got the smaller brakes I went with wheel cylinders for the JD6 - but it doesn't fit. The wheel cylinder I took off looks more like the 13" brake version (JD7?)

    Anyway, is it possible to figure out the RPO codes for the truck by the VIN?

    And where can I get the little bolts that hold the wheel cylinder to the backing plate - these are trashed? :(
     
  2. atho

    atho 1/2 ton status

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    Nope. The VIN just tells you the basic stuff.

    I think it was Pontiac that you could find that stuff out with the VIN. I know you can order a resto pack from GM (for a truck) and it will basically decode the VIN for you, but I think Pontiac went so far as to record options and even take pictures of the cars when brand new. Of course, maybe I am high on glue and didn't hear/see/remember that right.
     
  3. diesel4me

    diesel4me 1 ton status Premium Member

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    Dealer??

    The local GM dealers in my area always ask for the VIN# when you call for parts..most trucks are listed in their computers as to what they had for options..but I dont know how many years back the listings go..

    At the parts store,I contfronted this question os a daily basis..if the original options list was missing(usual case scenario),I'd have to use the shoe sizes,wheel cylinder bores,and truck GVW to figure out if it was a JB-6,etc..

    Its listed in the parts catalog near the front of the book,which "J" options had what size shoes and wheel cyl.bores.at least they used to be,when catalogs were used rather than computers..they also had to have a whole page explaining the "C","K","R" and "V" designations on the 88 up trucks...:rolleyes:
     
  4. sandawgk5

    sandawgk5 3/4 ton status

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    The only real difference between the 2 brake systems is the angle that the brake line connects to the wheel cylinder and I believe the JD7 wheel cylinder has a larger bore by 1/8".

    Ira
     
  5. Fubeca

    Fubeca 1/2 ton status

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    On my truck the backing plate has a little bracket with two bent ends that fit closely on either side of the wheel cylinder and the rubber boots fit inside of the bore of the cylinder. On the cylinder I bought the rubber boots fit around the cylinder and don't seem to fit in the space between the metal bracket.
     
  6. sandawgk5

    sandawgk5 3/4 ton status

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    It is hit or miss on those. The bores are the same and the boot is a tight fit with the backing plate but they are the same part number as the other ones. They changed how the seal attaches. I went to several store and found the ones with the internal seal just for personal preference.

    Ira
     
  7. sandawgk5

    sandawgk5 3/4 ton status

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    Here are the 2 different wheel cylinder boots. Ignore the angle of the brake line hole. Identical part numbers and I recieved one of each everything is the same except for the style of the seal as denoted in the pictures.
    [​IMG]

    [​IMG]

    Ira
     
  8. Fubeca

    Fubeca 1/2 ton status

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    Okay - I thought maybe they had just changed the design of the rubber seal. Then I looked online and saw the 13" version looked the same as the one I had on my truck - and then I got worried that I'd gotten the wrong part. I'll play with it some more tonight and see if I can get it to fit between the bracket.
     
  9. sandawgk5

    sandawgk5 3/4 ton status

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    Ya we even took one apart in the store and miced it and everything measured out the same as the old one I took off.

    Ira
     

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