differance in factory brake codes

[milspecjimmy]

what is the differance with these brake codes?

JB7
JB8
JD7

 

[70~K5]

[ QUOTE ]
what is the differance with these brake codes?

JB7
JB8
JD7

[/ QUOTE ]

From my '77 Chevy service manual.
JB7 Front disc12.50x1.28 rear drum13.00x2.50
JB8 Front disc12.50x1.53 rear drum13.00x3.50
Don't have a JD7 for this year.
In 77 K 3/4 ton came with either JB6 or JB7 depending on the GVW. 1ton K came with JB8, but 1ton C came with JB7 or JB8 depending on the GVW.