Chevy C10 brake booster

[wrangler160]

Hey guys, I have a 1981 Chevy C10 that I am in the process of rebuilding and almost have it driveable with the exception of one thing...brake booster...

I went to the parts store to buy a new booster and they asked if it was a JB5 or JB3 (I didn't know the difference) they told me to check the sticker in the dash and it would tell me. When I checked the sticker it said J50 and no one has been able to tell me anything about J50 brake booster. Has anyone else had this problem or can someone shine some light on this for me? Thanks.

[Keith Seymore]

J50 is the merchandised (customer selectable) RPO for power brakes; JB3 and JB5 are subsets (additional detail) based on that. JB3 is the small 1" rotor; JB5 is the 1.25" rotor.

I would recommend the JB5 booster. We built very few JB3s.

Here is the brake system release chart (for a '74, and for an '87) for reference if you would like to review it for a bit more detail.

K

[Keith Seymore]

Do you know your GVW?

It looks like for '81 JB3 = 5200 lbs and JB5 = 5600 lbs.

K

[THE "10" SILVERADO]

Like Kieth said go JB5. My sheet said J50 as well and that's what I went with.

[wrangler160]

Keith I do not know the GVW on the truck. They truck has been very confusing. The title says it is a 3/4 ton however it is a short/wide bed that came with a 305 so I don't see how it could be a 3/4 ton. The VIN on the dash is rusted so it is very hard to read. I am going to try to find a way to clean it so that I can check it against what’s on the title. Also it has the 11" rear brake shoes; however there is a brake bar in the setup and the guy at the parts store said the brake bar was only for the 11 3/4 inch brakes. So it saying that the booster is a J50 just threw me for another loop. I did hear that the JB5 is the more popular of the brake boosters. Thanks for your help.