Refreshing the rear brakes on my 1949 3800 - There is a gasket that fits between the hub flange and the brake drum. Are these still available somewhere? I can't seem to find a name or identify them.
Brown paper grocery bags are perfect for making thin gaskets like that one. If you lay the piece of paper on a drum and tap the paper with a small hammer around the edges of the center hole, lug stud holes and retaining screw holes you will just have made a perfect gasket in about one minute.
Why are they there in the first place? There's no way to seal the rotating gap between the drum and the backing plate, so gasketing the junction between the drum and the axle flange seems to be a fruitless effort! Jerry
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Why are they there in the first place? There's no way to seal the rotating gap between the drum and the backing plate, so gasketing the junction between the drum and the axle flange seems to be a fruitless effort! Jerry
I am not looking for an argument, and, I am no expert.
GM shows/lists those paper gaskets in the Master Parts Catalog: in Group 6.819 GASKET Wheel Hub (front & rear).
My understanding is that the "gasket" paper was/is used to help avoid "rust weld" of the drum and the backing plate.
X2 ^ on the above post. There is another poster that is trying to get his drums off. If you do not use the gasket or some never seize the drum can actually freeze to the axle. The next time you will have a nightmare getting you drum off. The gasket is not really sealing any thing. It is more to prevent a bond.
I just installed my drums on my ‘52 3100. (I know this post is about a 3800 but suspect it may still apply). I just went thru replacing axle oil seals and bearings. On the back side of the axle flange, is a stamped steel part called a oil deflector on the 3100 and called an oil slinger on the 3600/3800. The purpose of this deflector (on the 3100) is to catch and divert any axle fluid that weeps past the oil seal and direct it out a hole in the axle flange so it doesn’t contaminate the brake shoes. The brake drum also has that hole to pass any leakage to the outside of the drum. Without a gasket between the axle and the drum to create a seal, some of that fluid could potentially still get inside the drum.
EDIT: The pictures show the oil deflector, the hole thru the axle flange and the hole thru the drum and the gasket I made out of a brown paper bag. The drum has a tab that I assume if it was bent over would prevent you from installing the drum incorrectly blocking the weep hole.
Now I’ve never worked on a 3800 and do not claim to be an expert, but the “49 - 51 Chevrolet Truck Shop Manual” shows that gasket and states the importance of insuring a seal between the drum and hub by replacing it with new, but stops short on telling you the reason why.
Last edited by Phak1; Sun Nov 08 2020 12:58 AM.
Phil Moderator, The Engine Shop, Interiors and Project Journals
I left said gasket off my 3800 HO72 axle on one side but kept i on the other. The side with the gasket suffered a hub-seal failure and I noticed oil leaking onto the outside of the alloy wheel through the decorative/cooling holes. I pulled it all apart and the reason for the gasket quickly became apparent. There are holes in the hub that line up with holes in the drum. These holes had ducted the oil to the outside of the drum where it runs through a little channel to the inside of the wheel. Without the gasket, it would have leaked into the brake assembly ruining the shoes.
I fixed the leak and pulled the other side apart and installed a home-made gasket. Some axles have a sheet-metal dish under the wheel cylinders that will catch and duct any leaking brake fluid out through a hole in the backing plate; not HO52/72 axles unfortunately.
1951 3800 1-ton '62 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971. In the DITY Gallery
I left said gasket off my 3800 HO72 axle on one side but kept i on the other. The side with the gasket suffered a hub-seal failure and I noticed oil leaking onto the outside of the alloy wheel through the decorative/cooling holes. I pulled it all apart and the reason for the gasket quickly became apparent. There are holes in the hub that line up with holes in the drum. These holes had ducted the oil to the outside of the drum where it runs through a little channel to the inside of the wheel. Without the gasket, it would have leaked into the brake assembly ruining the shoes.
I fixed the leak and pulled the other side apart and installed a home-made gasket. Some axles have a sheet-metal dish under the wheel cylinders that will catch and duct any leaking brake fluid out through a hole in the backing plate; not HO52/72 axles unfortunately.
I agree this assessment is correct. I am searching for the OEM gasket and I guess I will have to make one. I don't have section 6.819 in my parts book either. Anyone know the part number to fit the rear drum on my 66 K 20?
