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so I live in the snowy/salty side of town in the winter, I see plenty of rusted out trucks. it saddens me. So my 22 2500 HD I went with aftermarket undercoating through the dealer. a year later i'm under the truck, notice the undercoating stops at the rear wheel wells. figured i'd start at the dealership. 

they told me GM puts some wax undercoating at the rear wheel wells and aftermarket undercoat wouldn't stick to the GM applied undercoat. I asked how long has GM been doing that, she said forever. 

So we have a known non working process that stops my additional $ from solving my concern!

please explain if you understand.

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1 hour ago, Hoginedgewood said:

so I live in the snowy/salty side of town in the winter, I see plenty of rusted out trucks. it saddens me. So my 22 2500 HD I went with aftermarket undercoating through the dealer. a year later i'm under the truck, notice the undercoating stops at the rear wheel wells. figured i'd start at the dealership. 

they told me GM puts some wax undercoating at the rear wheel wells and aftermarket undercoat wouldn't stick to the GM applied undercoat. I asked how long has GM been doing that, she said forever. 

So we have a known non working process that stops my additional $ from solving my concern!

please explain if you understand.

Only thing that's undercoated is the frame with the heavy wax coating the axles are a paint type undercoating and yes, he is right aftermarket undercoating won't stick to the part that's undercoated. Anything that's part of the under body bad cab etc is paint.

Edited by Silverado4x4
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The wheel wells are not undercoated from the factory. Just plain body color paint. 
fluid film sticks to the factory wax, and contrary to what a couple have said, doesn’t remove the factory wax. 
 

I didn’t coat the whole frame but I did test a few spots and it doesn’t phase the wax. 
 

I used Fluid film on most other areas under my truck. 

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No need for it down here but my northern customers like using AMSOIL's Heavy-Duty Metal Protector.  It doesn't effect the factory wax coating.  It's my understanding 6 cans will undercoat a 1500.

Most down here use it on their boat trailers since they are in salt water.  Keeps the springs in great shape.

 

https://www.amsoil.com/p/heavy-duty-metal-protector-amhsc/?zo=521390

 

image.thumb.jpeg.bf83d5882e22c5b717502e57f01745b2.jpeg

Edited by Black02Silverado
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From Minnesota and I got my 2023 High Country undercoated........everything here is coated white in the Winter and it's not snow!

They coated everything underneath and yes it does stick to the factory "wax" coating just fine. 

 

The added benefit I never thought about.......it helps a lot with sound deadening!

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Posted about this previously, so the short version.

After paying for the undercoat “special” from the dealer, I did some research and found issues with the product. Went back to the dealer to cancel the product and got into a long discussion during which the dealer did not want to cancel, after which the rep finally agreed to contact the GM rep, who replied that GM does not recommend any after factory coating even that applied by the dealer and advise it likely will make rusting worse. Upon receipt of this email, the dealer cancelled the order.

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I undercoated my last truck and will do the one I have now mostly because I have little faith in the GM coating on the frame, every used truck I looked at that had been through a winter had lots of rust on the frame and the  GM coating was pretty much gone. It rubs off anywhere it gets touched and even car washes removes it too easily leaving bare metal exposed.

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The rubberized stuff like Zebart? Never again.... Eric O from south main has a pretty good video on why. I agree with everything he says here since i have experienced it myself. Had a truck done this way and within 5 years the frame was coming apart and the truck was junk. Been using fluid film ever since and had no issues. If i still lived in the salt belt the fluid film place would have been the first stop for my 2024. I will have it done next time i'm in the north east with the truck but for now here in Florida i should not need it... I will spot spray any places that the wax has moved or come off.

 

 

 

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  • 1 month later...

Now on my  4th. GMC.  First new 2013 3500HD, saw the frame wax coating peeling off after a year. Saw another '13 at my dealer, bed removed, and cab on two post lift high in the air. Asked Bill the service manager as this was also a Duramax, what's up with that truck ??  Said re-coating the frame.  What ??   Thats when I got under mine and saw the black wax, still very sticky, peeling off in sheets.

Asked is this a recall ??  Bill said a "silent one". GM will pay for, ONLY if the owner complains !!!!

Woolwax ( same company as Fluid Film ) told me, this is still an ongoing GM truck problem. The frames are wax dipped as raw oily steel, and the wax will not stick. Frames should be chemically dipped first in an oil cleansing bath, that phosphate metal etch preps the steel, Before the wax dip, so it will adhere.

I just Woolwaxed my '24, all sheetmetal , wheel wells with liners removed, rockers, and  door cavities. Woolwax says wait two years for the GM frame wax to peel, then use their process on the frame areas then. It will not mess up the Gm fame wax chemically, as it is pure Lanolin, but just a waste of product and $$ on top of the GM frame wax , to do to early, only to peel off with the GM wax.

As I understand it, the Lanolin based products, will creep into seams, is chemically inert to not cause paint damage or to wiring.

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On 8/5/2023 at 5:35 PM, Silverado4x4 said:

Only thing that's undercoated is the frame with the heavy wax coating the axles are a paint type undercoating and yes, he is right aftermarket undercoating won't stick to the part that's undercoated. Anything that's part of the under body bad cab etc is paint.

I posted this in a few areas. The GM frames are dipped in the black wax, on bare un-cleaned , oily steel, from the stamping process.

As the steel was not cleaned before dipping in wax, it will not adhere well. Over time starts peeling off.

Even my new 2013 3599HD  and 2016 2500HD, the wax that was peeling off, stuck to my fingers and under fingernails. Hard to get off, still sticky as heck. Wax GM uses is not the problem, it's the lack of metal surface prep to help it stick.

GM and other mfg's. state the extensive sheetmetal paint process, requires "No Further Preventative Measures". So the Marketing Says.  Horse Pies.  I see every brand of truck in the North East with extensive sheepmetal corrosion, as Salt, Calcium Cloride is used on the roads.

Any lanolin based rust proof product is cheap insurance. Spray the heck out of your vehicles.

FYI: Woolwax just released a new Lanolin product called "Creep & Crawl".  Just tried it on my NOS '61-'71 Dodge rocker panel, still on the shelf. Put a little in the bottom spot weld pinch seam area, After a day, it was migrating upward, against gravity. Going to use it on all my vintage vehicles after seeing this.

 

KP.

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mine never see's salt but i did the entire frame/ floor pans/inner wheel whell's and everything under the bed in duplicolor spray in bed liner. it stuck to the factory frame coating (or should i say on top of) really well. ill most likely do the fluid film inside the rockers next. i think an ounce of prevention is worth a pound of cure in situations like this. or maybe peace of mind that you at  least tried to prevent it....

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