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.

school me on brakes...

Discussion in 'The Garage' started by 79k20350, May 31, 2006.

  1. 79k20350

    79k20350 3/4 ton status

    Joined:
    Nov 22, 2004
    Posts:
    7,757
    Likes Received:
    1
    Location:
    Ct
    I know the basics in differacnce between the systems but when it comes to jb5, jb6, jb7 and jb8, im a lost as fumes without his goats:eek1::haha: Im guessing the differances between them are weight ratings, but which is what rating and what does that entail aboot the system, master cylinder, booster etc...

    Im going to be swaping in a 3/4 ton 10 bolt under a blazer int eh next few weeks and need rotor/ calipers... came out of an 80 pick up ( i beleive cause its paired with a 14 bff and thats aboot the only year they did it...)

    Ok ive come up with jb8 as 1 ton hydroboost...

    jb7 is 8400lbs, if im not mistaken that the heavy 3/4 ton right? so with my 3/4 ton front end i could run these calipers...the search at autozone asked for jb5/jb6 or jb7 for calipers so i assume that the light 3/4 ton and 1/2 ton use the smaller calipers and the heavy (8400lbs) 3/4 ton use the bigger calipers right? But as far as i know all 10 bolt calipers are interchangable...right? so that means it doesnt really matter which i get. Id like to have the bigger ones though for more stopping power (obvioulsy ;)) Some one correct me if im wrong though...
     
    Last edited: May 31, 2006
  2. 79k20350

    79k20350 3/4 ton status

    Joined:
    Nov 22, 2004
    Posts:
    7,757
    Likes Received:
    1
    Location:
    Ct
    Btw my search aint working great otherwise i would have...
     
  3. 79k20350

    79k20350 3/4 ton status

    Joined:
    Nov 22, 2004
    Posts:
    7,757
    Likes Received:
    1
    Location:
    Ct
    This is nuts...ive read 6 or 7 old threads and in half they say jb7 is non hydro boost dana 60 brakes and in the other half jb7 is the heavy 3/4 ton brakes on a 10 bolt. Anyone KNOW for sure, not think, but KNOW! i dont wanna order the wrong caliper:o
     
  4. hunterguy86

    hunterguy86 1/2 ton status

    Joined:
    Jan 10, 2005
    Posts:
    2,477
    Likes Received:
    0
    Location:
    San Marcos, Texas
    ttt as i need this info as well
     
  5. hack500

    hack500 1/2 ton status

    Joined:
    Sep 16, 2005
    Posts:
    523
    Likes Received:
    0
    Location:
    Templeton, Ma
    I know a caliper for an 8600gvw 3/4 ton has a slightly larger piston bore than a caliper for a 1/2 ton. 3 5/32" vs. 2 15/16"

    for the rear the wheel cylinders bores

    1/2 ton :15/16" (11 5/32")
    light 3/4: 1" (11 5/32")

    heavy 3/4" 1 1/16" (13")

    btw, a 14bff as an option in 3/4 ton trucks up through the early/mid 80's. don't know about the whole jb6/jb7 thing.
     
  6. BadBob

    BadBob 1/2 ton status

    Joined:
    Aug 14, 2005
    Posts:
    158
    Likes Received:
    0
    Location:
    Lyndon, KS
    According to my 77 FSM JB7 is indeed listed as the RPO code for both the HD 3/4 ton brakes and the base 1 ton brakes.

    This doesn't mean they're nessasarily the same caliper. GM used the same RPOs on all kinds of vehicles to refer to different parts (JB8 would have been 4 wheel disk on a camaro for instance). If you want to use the bigger ones you can do it, though I suspect the rotors might be slightly different in thickness. The brake flex hoses might also be different, but if you get the right ones for the calipers you end up with, they'll both mate to what you have on the frame side.
     
  7. 79k20350

    79k20350 3/4 ton status

    Joined:
    Nov 22, 2004
    Posts:
    7,757
    Likes Received:
    1
    Location:
    Ct
    First off, heavy duty 3/4 ton brakes are 3 3/32, not 5/32

    Brake hoses are the same, so's the rotor.

    The codes, jb5/6/7/8 what have you are not interchangable in the sence your talking (or at least they shouldnt be) They are signifying which brake system was on which truck) a jb6 on a 1/2 ton is the same as on a 3/4 ton. They only mean one thing...
     
  8. 79k20350

    79k20350 3/4 ton status

    Joined:
    Nov 22, 2004
    Posts:
    7,757
    Likes Received:
    1
    Location:
    Ct
    no one else????
     
  9. FWP

    FWP CRS

    Joined:
    Oct 11, 2000
    Posts:
    3,845
    Likes Received:
    3
    Location:
    Prescott Valley, AZ
    Not yet, I'm working on it.;) I'm tired of all the mis-info hanging around. I'll get to the bottom of it, as far as I can go, and post up a new thread with what I can dig up.
     
  10. randy88k5

    randy88k5 1/2 ton status

    Joined:
    Nov 8, 2004
    Posts:
    1,248
    Likes Received:
    0
    Location:
    Lynchburg, VA, USA
    Found this, might be of use...

    [​IMG]
     

Share This Page