GM 134551 nut for 70 tail lamp housing mounting studs

[Bill L.]

I am looking for a source that might have this GM nut. I need 13 of them.

They are the nuts that attach the rear tail lamp housings to the body on 70 an other C3 corvettes. I think only through 73. Only have a 70 AIM. The also attach the rear wiring harness to the tail lamp housing(s).

It is a 1/4-20 nut and has a unique thickness. They were bright zinc plated. I have a few originals. PO must have had this area apart and used the wrong nuts or just did not use any at all.

Thanks,


Bill

[Henry J.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

Bill:

It may be a long shot, but try contacting AMK Products Inc. They have fasteners listed by OEM (in this case GM) numbers. I have been lucky in the past.

[Bill L.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

Bill:

It may be a long shot, but try contacting AMK Products Inc. They have fasteners listed by OEM (in this case GM) numbers. I have been lucky in the past.

It is not in their catalog. I too have had some success with AMK. I will call because they may have them available in bulk and it i snot listed in their catalog.

Thanks, Bill

[Alan S.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

Hi Bill,
My 71 has a combination of 2 different nuts; perhaps the 134551 nut (1970), and the 120375 it was changed to in 71.
If you can't find the 551 you can have the six I have.
Regards,
Alan
DSC_0396.jpgDSC_0398.jpg

[Joe L.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

I am looking for a source that might have this GM nut. I need 13 of them.

They are the nuts that attach the rear tail lamp housings to the body on 70 an other C3 corvettes. I think only through 73. Only have a 70 AIM. The also attach the rear wiring harness to the tail lamp housing(s).

It is a 1/4-20 nut and has a unique thickness. They were bright zinc plated. I have a few originals. PO must have had this area apart and used the wrong nuts or just did not use any at all.

Thanks,


Bill

Bill------

1969 also used the 134551 nut for the tail lamp application. The ones on my car are known originals, whether they are 134551 or not. These are 1/4-20 nuts. They are 0.208" thick. They are of a "natural" finish (which, of course, results in rust).

The most unusual feature of these nuts is that on one side the points are "beveled" (just like most standard nuts) and on the other side, the nut is completely flat. Whether the installers endeavored to install them so that the flat side was the contact side, I HIGHLY doubt. Also, when these nuts are installed it would be virtually impossible to discern that the contact side was completely flat rather than with beveled points. I'd be amazed if any judge could tell the difference.

Standard 1/4-20 nuts in today's world are 7/32" thick (0.219") and have the points slightly beveled on both sides. I don't think that anyone could tell the difference once installed. However, if you want to get even more accurate, you could file or grind one side of the nut so that its thickness is reduced to 0.208". This would also have the effect of removing the bevels on the points of that side of the nut and, therefore, making it flat like the originals. I would not go to that extreme but if you wish, be my guest.

By the way, I can't find that the GM #134551 nut was ever available in SERVICE.

[Bill L.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

Hi Bill,
My 71 has a combination of 2 different nuts perhaps the 134551 nut (1970) and the 120375 it was changed to in 71.
If you can't find the 551 you can have the six I have.
Regards,
Alan
[ATTACH=CONFIG]52279[/ATTACH][ATTACH=CONFIG]52280[/ATTACH]

Very instructive. Perhaps I was not missing hardware. I can never be sure at this point. I may install as you found yours Alan.

Thanks,


Bill

[Bill L.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

Bill------

1969 also used the 134551 nut for the tail lamp application. The ones on my car are known originals, whether they are 134551 or not. These are 1/4-20 nuts. They are 0.208" thick. They are of a "natural" finish (which, of course, results in rust).

The most unusual feature of these nuts is that on one side the points are "beveled" (just like most standard nuts) and on the other side, the nut is completely flat. Whether the installers endeavored to install them so that the flat side was the contact side, I HIGHLY doubt. Also, when these nuts are installed it would be virtually impossible to discern that the contact side was completely flat rather than with beveled points. I'd be amazed if any judge could tell the difference.

Standard 1/4-20 nuts in today's world are 7/32" thick (0.219") and have the points slightly beveled on both sides. I don't think that anyone could tell the difference once installed. However, if you want to get even more accurate, you could file or grind one side of the nut so that its thickness is reduced to 0.208". This would also have the effect of removing the bevels on the points of that side of the nut and, therefore, making it flat like the originals. I would not go to that extreme but if you wish, be my guest.

By the way, I can't find that the GM #134551 nut was ever available in SERVICE.

Alan's post explains the different sizes I found too. I am thinking I should be all set given the information posted.

Thank you.


Bill

[Joe L.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

Alan's post explains the different sizes I found too. I am thinking I should be all set given the information posted.

Thank you.


Bill

Bill-----


I expect the reason that the nut was changed from the 134551 to the 120375 was that someone finally figured out that the features of the 134551 nut were not necessary and the assembly line workers weren't going to install it correctly anyway. So, the nut was changed to the very standard nut of GM #120375. This change might very well have occurred on the assembly line well prior to the time it showed up in the assembly manuals.

The GM #120375 is a 1/4-20 nut with a zinc finish, 7/32" thick, and GM 286M material grade. It had beveled points on both sides. You can find nuts absolutely identical to this in most hardware stores. Once-upon-a-time it was available from GM in SERVICE.

[Alan S.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

Hi,
I just looked at my nuts again, (can I say that here?), with Joe's info in mind.
All the nuts have the 'beveled' points on both sides so I guess they're all #120375, just 2 different thicknesses.
My photo shows that too.
Regards,
Alan

[Joe L.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

Hi,
I just looked at my nuts again, (can I say that here?), with Joe's info in mind.
All the nuts have the 'beveled' points on both sides so I guess they're all #120375, just 2 different thicknesses.
My photo shows that too.
Regards,
Alan

Alan------



The 120375 are 7/32" thick. If one of the ones you picture is that thickness, then it's a 120375. However, the other one must be some different and unknown part number.

[Bill L.]

Re: GM 134551 nut for 70 tail lamp housing mounting studs

Alan------



The 120375 are 7/32" thick. If one of the ones you picture is that thickness, then it's a 120375. However, the other one must be some different and unknown part number.

There must be something wrong with me. I just love these kinds of details.

Thank you for the education

Bill