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Old 02-13-2026, 11:30 PM   #1
Wellwood
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Source for Replacement Rear Drum Backing Plate

New to me 1978 axle set...rear drum backing plates are crusty...thought I'd replace, but looking at the Dr Google search results, maybe these are NLA?

TIA for your response.
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Old 02-14-2026, 04:16 AM   #2
franken
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Re: Source for Replacement Rear Drum Backing Plate

Learn to speak in sentences?
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Old 02-14-2026, 10:31 AM   #3
Wellwood
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Re: Source for Replacement Rear Drum Backing Plate

Well, thank you for that Franken...guess I'll just have to put you in the category of 'I don't have an an answer or suggestion, but I'll be an English/Grammer critic'.

Not all who type and speak the English language are required to meet your standard. The message is quite clear.
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Old 02-15-2026, 07:54 PM   #4
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Re: Source for Replacement Rear Drum Backing Plate

I understood fine, but can't help. I suppose if they don't have holes or rusted out I'd wirewheel and paint.
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Old 02-15-2026, 07:58 PM   #5
hatzie
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Re: Source for Replacement Rear Drum Backing Plate

Need a few more bits of information.
Axle type? 10 bolt, 12 bolt, 14 bolt ....
Axle production stamping alphanumeric code.
Drum size?
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RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
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Old 02-16-2026, 10:07 PM   #6
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Re: Source for Replacement Rear Drum Backing Plate

I'm a few hundred miles away tonight, but will post the stamped numbers when I return.

Knowns = 11" diameter with 2-3/4" wide shoes.
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Old 02-18-2026, 10:25 PM   #7
Wellwood
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Re: Source for Replacement Rear Drum Backing Plate

It is a 12 bolt GM rear axle.

Numbers cast in the housing are GM66 and 3896838 with an N.

I looked on the passenger side axle tube for stamped numbers, but apparently the paint on there is a bit too thick?
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