Help with Brake Drum Part Number

[Joe P]

I have a 66 K20 and can't to find a part number for the rear drum. It's an HO72 with 13 x 2.5 inch brakes, 8 lug. This Eaton housing is the wider version to accommodate single rear wheels. I do have a set of 13 inch drums on my dually Eaton but that housing is an inch or two more narrow and the drums are different. I have piled through the parts books, this website and the other one, and paid an online visit to suppliers. All drums listed are 11, 12 or 14 inch, no 13's. I wish to keep the original brakes on the truck. Drum brakes work well for me, especially in the rear, so no disc conversion. The old drums I have are not salvageable and any markings that were on them have disappeared with time and weathering. Is there anyone who has been down this dark alley that can offer a flashlight in the form of a part number? Appreciate your time and courtesy!

Joe

[The Rocknrod]

Does this work? https://www.stockwiseauto.com/centri...xoCwFwQAvD_BwE
Or try LMC part # 34-3960, Rear Brake Drum, 4 Wheel Drive 3/4 Ton 60-66
And since you have a K20 here's a guy that might help with other parts - https://torqueking.com/category/1960...series-trucks/

[Joe P]

Originally Posted by The Rocknrod

Does this work? https://www.stockwiseauto.com/centri...xoCwFwQAvD_BwE
Or try LMC part # 34-3960, Rear Brake Drum, 4 Wheel Drive 3/4 Ton 60-66
And since you have a K20 here's a guy that might help with other parts - https://torqueking.com/category/1960...series-trucks/

Thank you, appreciate the input. The Centric Drum is a 12 inch and it is the part listed in every book and catalog for my truck. I need a 13 inch drum for the single rear wheel. Dually 13 inch drums are easy to find but pricey. I have two new ones on my dually that I got from RockA. Perfect fit for the dually but not for the single wheel axle. I had not found the LMC link for drums, thanks for that. They don't list the size so I will contact them to see if its a 13 inch. Also the Torque King site is new for me so again thank you. I will let you know what I find.

[JPBrecheisen]

I think you might try 3754300

Raybestos 2009R

Parts book page attached

[Joe P]

Originally Posted by JPBrecheisen

I think you might try 3754300

Raybestos 2009R

Parts book page attached

The Raybestos 2009R is also a 12 inch drum. Still looking for a 13 inch, SRW. Best guess I can make from the parts book is 3831784, but maybe 3857752. But I cant's cross it to modern number. Frustrating.

[Short 3/4]

I understand your frustration as I went through this same thing a few years ago. Who would have guessed that brake drums for a Chevy truck would be the hardest part of my mechanical restoration.
I too prefer the original drums, and unfortunately the 3/4 ton 4x4 stuff is unique to that model and just about extinct.
A couple things I learned that you may already know as it looks like you’ve done a lot of research:
All 3/4 ton 4x4’s came with 12x2 drums front and rear, and unfortunately unlike the 1/2 ton’s they are not interchangeable.
There were no duelly or one ton 4x4’s in 66
Sometime in 64 or 65 they changed from a separate bearing housing with slide on drums to a one piece unit with the drums and bearing housing not separate.
I got a lot of help from a guy in Southern California that runs “Drum Garden” not sure if he’s still around, but very knowledgeable and he specializes in stuff that doesn’t exist anymore. Let me know if you can’t find him, I may still have info somewhere. None of the usual parts sources have drums for 3/4 ton four wheelers, I know cuz I talked to them all!
Good luck
Tom

[Joe P]

Originally Posted by Short 3/4

I understand your frustration as I went through this same thing a few years ago. Who would have guessed that brake drums for a Chevy truck would be the hardest part of my mechanical restoration.
I too prefer the original drums, and unfortunately the 3/4 ton 4x4 stuff is unique to that model and just about extinct.
A couple things I learned that you may already know as it looks like you’ve done a lot of research:
All 3/4 ton 4x4’s came with 12x2 drums front and rear, and unfortunately unlike the 1/2 ton’s they are not interchangeable.
There were no duelly or one ton 4x4’s in 66
Sometime in 64 or 65 they changed from a separate bearing housing with slide on drums to a one piece unit with the drums and bearing housing not separate.
I got a lot of help from a guy in Southern California that runs “Drum Garden” not sure if he’s still around, but very knowledgeable and he specializes in stuff that doesn’t exist anymore. Let me know if you can’t find him, I may still have info somewhere. None of the usual parts sources have drums for 3/4 ton four wheelers, I know cuz I talked to them all!
Good luck
Tom

Tom, thank you for spending the time to write a reply. I appreciate your input very much. I am still scratching my head on this but I think that the rear axle may have been changed at one time. It "looks" original and certainly it had been there for a long time as the U-bolts were rusted to the diameter of a pencil. Drums are definitely 13 inch. I got one of the correct (by the parts book) 12 inch drums just to be sure, but it does not fit at all. The drum from my 66 dually is the same 13 inch diameter and drill pattern but the hat portion of the drum is too high. It smacks the backing plate before the hub bearings are seated, and is way off, like by an inch or two. I cleaned up one of the original drums as it was a greasy, rusted mess. I'm going to let my local machine shop have a look at it to see if it can be cut. If that doesn't work I will see if I can get a parts guy to match it to something modern. I did find that the Drum Garden still exits. Looks like a good resource, but 3,000 miles from here. If (when) my local search fails I will give them a call. Thanks again!

[Short 3/4]

My guess is that you have the original housing and someone replaced the entire brake assembly in the rear with the 13’s. It’s really easy to do, I actually have 11” drums on the rear of mine that I pulled off my old 2wd to get the truck running while I was looking for the correct parts. I now have the right stuff, but always have something better to do than replace parts that are working. Probably someone in your trucks past wanted bigger rear brakes, or more likely couldn’t find the 4x4 parts so went to the local wrecking yard and made something work. The 12” rear drums were only used on 4x4’s for 60-66, never 2wd, so parts were always uncommon. There is an interesting thread somewhere on this forum that talks about all the brake interchanges possible for the HO rear ends. As I remember you can even swap brakes from a Dana 60, so seeing the “wrong” parts on a 50+ year old truck is not so unusual.
Anyway, this is a very long winded way of saying you have a lot of options for drums if you can just manage to also find the corresponding back plate and hardware.
Hope this helps
Tom

[Joe P]

Originally Posted by Short 3/4

My guess is that you have the original housing and someone replaced the entire brake assembly in the rear with the 13’s. It’s really easy to do, I actually have 11” drums on the rear of mine that I pulled off my old 2wd to get the truck running while I was looking for the correct parts. I now have the right stuff, but always have something better to do than replace parts that are working. Probably someone in your trucks past wanted bigger rear brakes, or more likely couldn’t find the 4x4 parts so went to the local wrecking yard and made something work. The 12” rear drums were only used on 4x4’s for 60-66, never 2wd, so parts were always uncommon. There is an interesting thread somewhere on this forum that talks about all the brake interchanges possible for the HO rear ends. As I remember you can even swap brakes from a Dana 60, so seeing the “wrong” parts on a 50+ year old truck is not so unusual.
Anyway, this is a very long winded way of saying you have a lot of options for drums if you can just manage to also find the corresponding back plate and hardware.
Hope this helps
Tom

Thanks again Tom for your words. Likely the brakes were switched somehow. As you said, the 4x4 had 12 inch brakes from the factory so something got changed. I am of the opinion that the entire rear was swapped with one from a C30 one ton that had single rear wheels, not a dually. I have considered changing the backing plates to the correct size, but I like the idea of the larger brakes, and also I don't want to deal with the bearing oil slinger that is pressed on to the axle that is there to divert leaking oil away from the shoes. This would have to come off as the backing plate will not pass over it. I am sure I could pull it off and push it back on, but as you said, if it is working, then leave it.

In the meantime, I cleaned the first original drum and wire wheeled it, then took it to the local NAPA guy. It measured 13.050. The machinist said max was 13.090 but I argued 13.190, no way to read the "max diameter" marking. I picked it up a couple hours later with 99% of the pits cleaned up - It looks quite serviceable, $26. It will work for now as I continue looking for new parts. Now I will move on to the other side.

Thanks again for your thoughts!