Tech: How to Identify Original, GM Replacement, and Aftermarket Body Panels (Fenders, Hoods, Doors)

[legopnuematic]

I thought this might be a good idea to create a knowledge base on the differences between factory, GM replacement, and aftermarket body panels as there does not seem to be a good reference for such (that I know of). Basically any body panels (hoods, fenders, doors, fillers, bed panels, tailgates, bumpers, that kind of stuff). Please feel free to add information that you have about the differences between them.

Hopefully this might help someone be able to positively identify if something being passed off as a GM part is truly a GM part and not a reproduction.

 

[legopnuematic]

Starting with fenders, atleast for 73-80.

-Factory 73-80 fenders
-No GM Stamp along rear seam that faces door
-Spot welded nuts visible as seen in photo #2
-Heavier construction

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[legopnuematic]

NOS/GM Replacement fenders
-GM stamp on rear seam facing door
-Spot welded nuts visible
-GM parts sticker
-Heavier construction

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[legopnuematic]

Aftermarket
-No GM stamp
-Spot welded nuts hidden behind skin
-Light weight compared to GM fenders
-

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[bucket]

Good info! I never noticed that about the spot welded nuts on the aftermarket fenders.

 

[shiftpro]

I just tap twice with my knuckle. Original sounds like 'tunk tunk'...
aftermarket goes 'tank tank'..

 

[MylesNT]

Guess who just found out the fenders he bought as OEM, aren't?

This would be a good sticky somewhere.

 

[78C10BigTen]

NOS/GM Replacement fenders
-GM stamp on rear seam facing door
-Spot welded nuts visible
-GM parts sticker
-Heavier construction

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My fronts do have the gm stamp, no stickers though. Where were the stickers placed?

 

[bucket]

I need to go see where my GM stamps are on my fenders and look at the doors too. They are for sure NOS, as I bought one from GM and the others were still in the GM boxes when I got them.

I can see how my aftermarket fenders compare too.

 

[dhenderz]

Small detail, but for those interested in the technical details. The original GM nuts are not weld nuts. They are self-pierce nuts. They come on a wire roll and are installed by a press machine that simultaneously stamps/cuts the hole and presses the nut into place.

The aftermarket uses weld nuts because it does not make sense to invest in the dedicated capital machinery for every single part they produce. Instead it is cheaper to punch the hole during the stamping process and then just weld the nut in place.

http://fasteneradvance.com/gallery-fastener-advance/

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[legopnuematic]

My fronts do have the gm stamp, no stickers though. Where were the stickers placed?

From what I've seen, there is no set place for the stickers. On my set one was in the inside about center and the other looks to have been where the inner fender meets the fender in the wheel arch. It appears that they never put stickers on the exteriors of panels however. (or at least the NOS doors I have seen had them where the door panel covers and my NOS bumper has one on the inside). Chances are if they are on a truck the stickers are long gone.

 

[trukman1]

If you can't find OEM GM panels I've found, from talking to body shop guys, that they prefer Key Parts panels. The best price I've found is FixMyRust. They combine shipping on over sized parts also so you only pay once. At least they did when I purchased mine. Body men claim they fit the best and are the right thickness, thereby reducing labor hours. YMMV.

 

[CSFJ]

If you can't find OEM GM panels I've found, from talking to body shop guys, that they prefer Key Parts panels. The best price I've found is FixMyRust. They combine shipping on over sized parts also so you only pay once. At least they did when I purchased mine. Body men claim they fit the best and are the right thickness, thereby reducing labor hours. YMMV.

Good to know, but this thread is about how to identify a real GM panel from a repop, not about who makes the best repop. There's already plenty of those threads out there.

 

[Almcphee]

Thanks trukman1......
I learned something today and haven’t searched for those “how to identify “ threads .

 

[yevgenievich]

I have what looks like an original gm 73-79 fender for sale and every body seem to be asking for gm stamp. There must be a believe that original also has a stamp