The Stovebolt Site Forums The Shop Area Paint and Body Shop What is the best undercoating product?

Hi Guys,
I am at the stage that I am ready to apply undercoating to my 1952 GMC Suburban project. It was originally a US Army Ambulance and the original undercoating held up amazingly well for 60 years.
I've scraped it all off, but I need some recommendations for a modern product to apply under the body. Remember, some of the area is wood, the rest metal, so it must have good adhesion to both.
Someone recommended a bed liner product, any thoughts on that?
Thanks in advance,
Possum

I used 3M rubberized undercoating in rattle cans under my truck. Very happy with it. I think there were 2 different grades available, get the more expensive grade, it's more rubbery, goes on thicker.

To me the best undercoating is no undercoating. It can hide rust issues. Just wash the underside of your truck on a regular basis.

I agree with Drew. We use bedliner all the time even on very old trucks but only on newly blasted and properly prepped metal. If you have not done that you are better off just cleaning it every so often. The cheaper coatings will absolutely absorb moisture and will cause you problems down the road. Not an implication of 3M products, just an overall observation.

Personally I will cut every corner possible except where hidden rust is a concern. To me that is the best way to really preserve a vehicle.

Good luck.

I strongly agree. Oil works wonders, just a light coat.

Oh and to actually answer your question we have had good luck with SPI products. They are durable but still soft enough to not chip easily. You would want to buy their application gun to make it look best.

Your original question makes me think you care enough about your vehicle for me to make this comment to you: stay away from the rattle can stuff. It may work fine for some people but if you want to mostly forget about it after you apply it this is not the best choice. Again at that point you would be better off giving it a good cleaning every so often.

Good luck.

Not to contradict, but my truck was undercoated when new in 1953, all the metal looks new today, it would be long gone otherwise. It will get glassed beaded then etch primed and re-undercoated when the time comes.

No contradiction there as you apparently have a vehicle with undercoating applied when new. OP has scraped the undercarriage of a 60 y.o truck - and we are not sure to what extent. If he undercoats properly prepped metal he should have little to no worries. If he applies when there is crud on the undercarriage he would be better off saving his money and washing every so often as advised. Same as if we were talking about paint on the surface.

Understood, thanks for the clarification.

In a dry climate like Sutter Creek, CA; I would not worry about undercoating. I think DrewP's recommendations are spot on.

No undercoating is fine unless you drive your truck anywhere but your paved driveway. These old trucks have no inner fenders like the newer ones. If you do drive your old truck, I guarantee you will eventually get a large piece of gravel or a small stone caught in your tire tread and then flicked up in your rear fender well. Without any type of undercoating, chances are you will get a nice star in your paint job. I realize that undercoating will not guarantee protection, but it could sure minimize damage. 56PICUP was a rock victim so...just a thought.

My truck has a nice coating of 80w90.

That and straight 30 weight.

Point well taken 56picup, somehow I missed thinking of that. Sometimes the obvious is so obscure.

FWIW: On the inside of my fenders was a thick layer of roofing/road tar. I think it was a common fix for preventing stars in the paint and the like
Kept things quiet on gravel roads and provided metal and paint protection at the same time.
It was still good when I stripped it off the metal was like a baby's butt and without a doubt the hardest thing to remove on the entire truck. I'd take having to remove five rusted broken bolts over cleaning down to metal one tarred fender anyday.
I wonder if rubberized spray on bedliner will hold up as well for as long...

I like 3M Body Shutz. I used it on the bottom side of the cab and running boards. I will also use it on the inside of the front and rear fenders AFTER they are mounted. The inner front fenders will remain paint only. The bed side panel inside the rear fender will get the undercoating. Also, Body Shutz is an affective sound deadener.