Jb5, jb6, jb7 master and booster interchangeability

[kenny78]

My 82 K20 has an 82 c10 cab on it. It was that way when I bought 7 years ago. The drivetrain has jb7 calipers and rear drums and the MC is steel and looks like the jb7. 5 years ago my booster went bad and I am pretty sure I grabbed the booster off of the 78 parts blazer. I was ignorant of any difference other than vacuum and hydro boost back then.

The pedal feels normal etc but in planning some maintenance I was researching parts and keep seeing things like pedal rod differences. Forum chatter also leaves me confused.

Anybody have any clarity

 

[chengny]

My 82 K20 has an 82 c10 cab on it. It was that way when I bought 7 years ago. The drivetrain has jb7 calipers and rear drums and the MC is steel and looks like the jb7. 5 years ago my booster went bad and I am pretty sure I grabbed the booster off of the 78 parts blazer. I was ignorant of any difference other than vacuum and hydro boost back then.

The pedal feels normal etc but in planning some maintenance I was researching parts and keep seeing things like pedal rod differences. Forum chatter also leaves me confused.

Anybody have any clarity

Not sure what you are asking for clarity on.

If the brakes have exhibited normal pedal feel, and have consistently delivered design performance (over a period of 5 years) - what are your concerns?

 

[kenny78]

Sorry if I wasn't clear. Does the master and boosters interchange between these three series? Or if it comes time for replacement should I buy a matched set for jb7? Will a different booster interface with the cab correctly?

I am trying to be proactive about maintenance because this is my service vehicle now

 

[chengny]

Sorry if I wasn't clear. Does the master and boosters interchange between these three series? Or if it comes time for replacement should I buy a matched set for jb7? Will a different booster interface with the cab correctly?

I am trying to be proactive about maintenance because this is my service vehicle now

Does the master and boosters interchange between these three series?

By "series", do you mean the 1982 2WD, 1982 4WD & 1978 *WD? With some exceptions, brake ratings are primarily based on GVWR. whether a truck is a C or K isn't a factor. From what I have observed looking at parts lists, the JB ratings are grouped like 1, 3 & 5, 6 & 7. All three groups use parts with different numbers than the other groups.

But I'm not exactly sure what the situation is (i.e. what JB ratings are involved) or what you are trying to do. So, I think it's best if I just provide the raw data and let you figure it out.

First step: use the brake rating and ID charts below - to identify the JB rating designation for each vehicle involved. I will have to continue this in the next post box due to a 5 image per post limit.

Body ID charts:

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Brake rating matrices:

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[chengny]

MC & PB part numbers for model year 1982:

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And all the possible MC & PB part numbers for the 73 -78 model years. That parts manual didn't have those handy charts like above:

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[kenny78]

Chengny, thank you for taking the time to post all of that.