GM #3765425 hex nut dimensions

[Gary B.]

Does anyone know the dimensions of the hex nut GM 3765425? I know it's 7/16-14, but I don't know the thickness or if the across the flats dimension is typical for 7/16 or if it's a light nut. The only place it appears in the '66 AIM is for the rear differential front mount. The repro bolt kit for that application that I purchased contains a distorted thread nut. And I'm suspicious that's not correct.

Thanks,

Gary

[Joe L.]

Re: GM #3765425 hex nut dimensions

Does anyone know the dimensions of the hex nut GM 3765425? I know it's 7/16-14, but I don't know the thickness or if the across the flats dimension is typical for 7/16 or if it's a light nut. The only place it appears in the '66 AIM is for the rear differential front mount. The repro bolt kit for that application that I purchased contains a distorted thread nut. And I'm suspicious that's not correct.

Thanks,

Gary

Gary-------


I do not have specs on the GM #3765425 except that it's 7/16-14 thread and GM 301M material grade. It also had applications for the front upper control arm for many Chevrolet applications but not Corvette. I am virtually certain, though, that it was not a self-locking type nut.

It was discontinued from SERVICE and replaced in June, 1971 by 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. I suspect the 3765424 was similar with the possible exception of the finish.

By the way, you will note that the 3765425 is used in conjunction with a lockwasher for the front differential mount application. In the vast majority of applications , a prevailing torque lock nut would not be used in conjunction with a lock washer.

[Gary B.]

Re: GM #3765425 hex nut dimensions

Thanks Joe. AMK repros a heavy, 7/16-14 nut similar to 9424985 in terms of dimensions, but only in black phosphate/oil. Maybe 3765425 was black phosphate? The '66 TIM&JG doesn't mention that nut or its finish.

Gary

[Alan D.]

Re: GM #3765425 hex nut dimensions

Would guess from this info it's cadmium, however the note of it being 300-M steel may mean it's a natural steel finish.
I do not know how to interpret that, Joe probably does.

[Gary B.]

Re: GM #3765425 hex nut dimensions

Alan,

Thanks for that list. It sure suggests to me it was cadmium. I think 300-M indicates it's grade 8. That was long before grade 8 nuts and bolts were yellow.

Gary

[Joe L.]

Re: GM #3765425 hex nut dimensions

Alan,

Thanks for that list. It sure suggests to me it was cadmium. I think 300-M indicates it's grade 8. That was long before grade 8 nuts and bolts were yellow.

Gary

Gary------


GM 300M or GM 301M = SAE grade 8.

The above-referenced listing would indicate that the GM #9424985 was cadmium plated. However, other GM references I have indicate it was copper plated. Plus, I have a large number of NOS GM #9424985 [none for sale] and all have a copper plated finish. Of course, it's possible that the finish spec changed over time. That would be unusual, though, because in the vast majority of cases GM assigns a different part number for the same basic fastener if there are different finishes.

[David B.]

Re: GM #3765425 hex nut dimensions

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."

[Gary B.]

Re: GM #3765425 hex nut dimensions

But back to the GM #3765425, I'm going to assume that was cad or zinc.

Gary

[Joe L.]

Re: GM #3765425 hex nut dimensions

But back to the GM #3765425, I'm going to assume that was cad or zinc.

Gary

Gary-----


Well, if the above-referenced table was incorrect regarding the 9424985, then I suppose it could be incorrect regarding the 3765425. Actually, I believe there may be several finish inaccuracies in this table.

[Gary B.]

Re: GM #3765425 hex nut dimensions

Joe,

Something was different between the two nuts and it seems like a different finish could be a reasonable assumption. Copper plating is pretty unusual. My bet is the earlier nut was not copper plated, and cad would make sense.

Gary

[Alan D.]

Re: GM #3765425 hex nut dimensions

So here is a 1983 catalog showing the 9424985 (gone is the 3765425) finish in copper. I'll look around a little more for the 37...