NEED HELP!! 1973 Dually Brake Problems

[SCOTI]

Originally Posted by Crcrft78

I am at my absolute wits end with this F***ING truck and its brakes. Does ANYONE know for a fact if 74-75 brakes can be bolted up to the 73 without any problems. I'm ready to send this thing to the f***ing scrapper.

Any later model C30 (-91) will interchange. You'll need to try & keep things similar or issues will arise. Ex: Switching from a vacuum app to Hydra-boost requires a different pedal ratio (thus different pedal or different location of pin on the pedal). On my 89, I swapped from HB to a vacuum set-up & needed to adjust the pedal ratio.

[Crcrft78]

Ok I guess I wasn't clear on what I was asking. Can I just swap to 74-75 rear dually drums and brake shoes without having to change my 73 rear axle? Does it require swapping backing plates or swapping anything at all or can I just use the 74-75 brake parts instead of 73 brake parts?

[hatzie]

You can likely swap out everything from the backer plate to the hub and axle onto your unit. I'd find a donor truck with the same or better GVW Dana 70 from 74 -77 C30 Dually and use the whole unit drum to drum. Less time, probably cheaper, and it looks at a glance you'll get the more common 1" wider shoes.

From section 5.809 in the 73-78 parts books that you can download from the manuals link in my signature.

This is a 1973 ONLY part. They were $121 each in 1982... I can't find anyone that has the equivalent part from Raybestos or any other manufacturer.

73 C-3 (Dual Rear Wheels w/Dana Axle) 6258610 DRUM ASM., rear (13" x 2.50" brk.)

When you look at the Illustration catalog page it'll either have a part number or a section number. If an actual part number is listed you're done... A section number means you need to go to that section in the Parts catalog to find year and model specific info.
The part listing may go on for several pages after the illustration depending on what part you're looking at...

Illustration book page... The DRUM is #36 and it points to 5.809


Parts book page... page down to the description that matches your rig.

[Crcrft78]

When you look at the Illustration catalog page it'll either have a part number or a section number. If an actual part number is listed you're done... A section number means you need to go to that section in the Parts catalog to find year and model specific info.
The part listing may go on for several pages after the illustration depending on what part you're looking at...

I'm not quite following along. So can I look up the part and see what will interchange or do I just get the description of the part. I see the drum listed for what I believe is my truck 73 C-3 (Dual Rear Wheels w/Dana Axle) 6258610 DRUM ASM., rear (13" x 2.50" brk.) as you listed but what is 19.0500 referring to in the GMC Group? I am trying to figure out how to read this.

[hatzie]

Originally Posted by Crcrft78

I'm not quite following along. So can I look up the part and see what will interchange or do I just get the description of the part. I see the drum listed for what I believe is my truck 73 C-3 (Dual Rear Wheels w/Dana Axle) 6258610 DRUM ASM., rear (13" x 2.50" brk.) as you listed

but what is 19.0500 referring to in the GMC Group? I am trying to figure out how to read this.

You have The Model Year, Model Description, Part Number, QTY/Vehicle, Part Description, and that last number in bold.

I've never worried about that last number. I've never been asked for that number and it doesn't affect part number lookup for me.
There is no such thing as Group 19 in the 73-78 light truck parts and illustration catalogs so that's not it.

If you're into trivia... Maybe a member that's worked in GM dealership parts or assembly will chime in.

As far as interchangeability goes...
#50 "Housing, Rear Axle" is in Section 5.387 of the parts book.
5.387 reveals that the C,K,& P full tons with Dual Rear Wheels, CKP-3, used the same housing from 1973-1977.
Experience has showed me that the 1ton dually pickup axles interchange from 1973 to at least 1980.
Make sure what Dually chassis you actually have;
Dually pickups have fiberglass wheel tubs that extend beyond the regular fleetside bed sides. Apparently from 1973-1977 the P series vans used the wide pickup dually as well... I'd measure before I liberated one of those.
Commercial Chassis Cab trucks look like a pickup cab but they use a narrower dually axle. I usually associate 1 & 1.5 ton Chassis Cab Duallys with Electric or Phone or Cable Company work trucks with flat sided boxy Reading etc steel work bodies but they could be ordered with commercial Aluminum or steel and plank flatbeds or stake boxes as well.

[Crcrft78]

Well today I finally got the truck back on the ground. It only took me a year or so to finish a brake job that should've lasted a couple of hours. Tomorrow i will post all the part #s for everything I used just in case anyone else has as much trouble as I did.

[Desert1957]

Sorry to ask this question now, but was all this problem at one particular parts store? Or did you travel around?

[Crcrft78]

I tried several brick & mortar parts stores including Rock Auto, Raybestos and other online sources.