2020-B1-8

Author Topic: '79 403 Oil Drain Plug Size  (Read 76 times)

Ghostrider

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'79 403 Oil Drain Plug Size
« on: March 24, 2020, 10:39:34 AM »
Does anyone know what the thread specs are on the stock oil drain plug? I wanted to install a new drain plug that is magnetic. My stock drain plug takes a 7/8" wrench. Looking at aftermarket plugs, they seem to be 1/2-20 with a 9/16" bolt head.

Thanks

Wallington

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Re: '79 403 Oil Drain Plug Size
« Reply #1 on: March 24, 2020, 06:36:54 PM »
Should be 1/2"- 20 stock as with most GM of the era. Aftermarket magnetic tips are often smaller head as mentioned.
I used the Gold Plug AP-01 on both my engine and trans with aftermarket pan. There are many cheap alternatives, the thread and seal usually don't match the quality.
« Last Edit: March 24, 2020, 06:42:18 PM by Wallington »

Ghostrider

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Re: '79 403 Oil Drain Plug Size
« Reply #2 on: March 24, 2020, 10:26:10 PM »
Thanks Wallington. So the aftermarket plug threads aren't up to snuff?

Wallington

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Re: '79 403 Oil Drain Plug Size
« Reply #3 on: March 24, 2020, 11:20:29 PM »
Some of the really cheap, chrome, Chinese etc have been known to weep or be undersize etc. I'm talking about the brandless ebay types not in a packet.

Re: '79 403 Oil Drain Plug Size
« Reply #3 on: March 24, 2020, 11:20:29 PM »
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