which brake caliper do i have?

[moneyeater]

Hello Square buddies,

i need help!
My truck rested for 9 month and now the front brakes don´t work properly anymore!
I tried to find out what caliper to get but there is no options sticker in the glovebox.
How can i find out wich caliper option is in my truck?
JB5, JD3, JD5, JB1, JB 3??????
It is a ´81 GMC Sierra Grande diesel with the 5.7 liter oldsmobile diesel (wich is not in there anymore)
Is it possible to decode the VIN to find out or is the a number on the calipers?

Any help would be greatly appreciated!
Thanks in advance
Volker

[Keith Seymore]

Here are the brake system release charts for an '87 (your '81 should be similar).

Normally we would need more details about your truck, specifically series (ie, C10, or C20) and GVW, but in this case it doesn't seem to matter.

Knowing nothing about your truck other than the picture in your avatar I would guess it is a JB5/JD5 brake system.

Calipers would be 18011030 and 18011031.


JB1 is manual brakes; JB3 is super light duty power brakes (we didn't build very many); JB6/JB7 are 3/4 ton; JB8 is one ton.

K

[Keith Seymore]

One other thing you might be interested in:

You can send your VIN and $50 to the GM Heritage Center Archives and they will send you the exact vehicle invoice for your specific truck.

It will include the options the truck was built with and individual pricing.

Link: http://www.gmmediaarchive.com/?page=3

K

[moneyeater]

Hey Keith,
thank you for the info.
The Truck is a C10 with a 5.7 l Diesel und hydraulic brakebooster and powersteering
3.08 Gears in the rear axle and Sierra Grande trim, wich is almost nothing i assume.
Unfortunately that is all i know but i´ll take the opportunity and let GM Heritage decode my VIN for more info.
Volker

[moneyeater]

tonight we pulled the wheels of the truck and looked for the problem again.
We found out that the calipers are fine - it is the proportion valve that doesn't work right.
Are they known to fail?
Ok it is 33 years old and has seen many miles but... could it be?
I had the rear drum brakes locking up in the past and now that may have been the first signs of failure i assume.
Can someone recommend a shop where i can get it from?
Volker

[Chevy1966]

You might want to have a look at the troubleshooting information here:
http://www.classicperform.com/TechBo...t.htm#testprop
You will see a section about testing the proportional valve, and resetting it if needed. Without doubt Keith is the expert, so he might have other suggestions... Rob

[moneyeater]

Thank you Rob,
this is helpful to understand that valve, but what causes it to getting stuck?
Volker

[Chevy1966]

Hi Volker, as for the cause of the stuck valve... in my case it was caused when one side of my master cylinder failed. I think this results in the valve piston to be shoved hard over to one side. There are probably other conditions which could cause the same result. Let us know how you were able to get your system running properly again. --Rob

[moneyeater]

Hi Rob,
since i couldn´t come by a propvalve in a reasonable time i started with new brake hoses and now it seems to be ok!
I still don´t know wich calipers i have but the brakes work fine now with the system flushed and new hoses!
Thanks for all your help!
Volker