Copper rear end tongue nut

[Joseph A.]

What years used the copper nut on the rear end tongue bolt?

[Gary B.]

Re: Copper rear end tongue nut

I believe that GM #9424985 nut was supposed to be used from 1967 through 1979 (or ‘82?). But I found one on my July build date ‘66, so it appears someone jumped the gun with using that copper plated nut.

Gary

[Joseph A.]

Re: Copper rear end tongue nut

I do not believe 9424985 is copper flaashed. My standards book states this nut is not copper flashed. I believe the copper nut is from 63 to possibly 65

[Gary B.]

Re: Copper rear end tongue nut

Joseph,

Are you sure?

In a 2019 posting Joe Lucia stated “…GM #9424985. The latter, which was used in PRODUCTION for the front differential mount application for 1967-79 Corvettes was a heavy hex (11/16" across-the-flats), 3/8" thick, 301M material grade, and of COPPER plating.”

David Bartush added: “GM #9424985 7/16-14 GM 301-M steel copper (finish) Class 2B thread
"GM 301-M: Nuts of this material are intended primarily for assembly with bolts conforming to GM 290-M or GM 300-M steel."
"Finish: Copper on steel: GM 4250-M Code OY, specification shall apply. It requires a flash deposit of copper by immersion coating or electroplating for identification or coloring."”

The nut used from 63-66 is given in those AIMs as GM 3765425, which was Gr 8 and likely either natural or cad/zinc.

If you check thru PartsVoice, it looks like there are several GM dealerships that still have a few example of 9424985, even though it is GM-discontinued.

Gary

[Joseph A.]

Re: Copper rear end tongue nut

You are correct I found another standard parts book that stated they are copper.