[finsfree]

I want to paint the undercarriage of my 2003 wrangler just because of preventative reasons. Can I just jack it up and paint it like it is or would it be better to detach the body from the frame and how big of a pain in the a$$ is that? Of course I'll be doing some prep work like sanding down the frame and axles before hand.

I'm not really concerned with the product as I already have something in mind.
https://www.amazon.com/gp/product/B...to-20&linkId=5d8e876b1badf98c211bc70255e7b29c

youtube.com video on the product.

 

[PDoyle]

Get some wire wheel disks for your cordless drill and go around the frame then prime and paint. Don't forget the skid plates The axles get most of the road abuse so you will do those again and again.

 

[BDW]

Rubberized undercoating is reputed to trap water and increase pockets of hidden corrosion. On an older vehicle you’ll never get to and remove every speck of corrosion in the crevices.

Some people like POR products, and oil based solutions like WoolWax or FluidFilm will creep into the crevices and protect even in places you can’t see.

 

[PDoyle]

I didn't mention Por and products like that because they get all over you when you want to get under the Jeep to work on it. I don't know how much creeps onto the frame holes. Paint can do the same.

 

[TheBoogieman]

The inside of the frame needs it first/most. I cleaned mine out and always use Eastwood internal frame coating. Afterwards, you can find much better stuff than Fluid Film. I use a wire wheel attachment on my drill for the outside of the frame, control arms, axles, etc.

 

[Shadownwpa]

Most of the worst places for rust are places where sand and moisture can sit and fester... like between the skid and the frame, inside shock mount brackets, under bump stops, those sort of places. I'm not sure where you're from but if it's in the rust belt you've probably already got hidden holes to fix on a 2003.

 

[JustinPierce]

POR is a paint, Wool Wax and fluid film are a nondrying corrosion preventative.
Wool Wax and fluid film are oily and can be a little messy, but POR is not.
I actually think a combination of POR or Chassis Saver and then an annual coating of Wool Wax or Fluid film is the way to go.
Unless you are doing a full body off the frame restoration and media blasting everything before priming and painting.

Painting an assembled chassis, you will never get 100% of the area properly prepped and you'll also never get 100% primer and paint coverage, or 100% adhesion. Painting assembled is mostly a cosmetic thing, not that you shouldn't do it. I just think most people feel all warm and fuzzy afterwards thinking that they have stopped the rusting potential, and that just isn't the reality.

I wouldn't use that undercoating, my choice would be Magnet Paints Chassis saver, Prepped as best as possible, Aluminum silver as a primer, then satin black topcoat. Then when it was cured, I'd spray every nook and cranny inside and out at least annually with Black Wool Wax. None of this is cheap and easy as blasting on spray bombs of undercoating, but I think it's probably the best bet for slowing down the rust without doing a body off restoration.

I haven't painted my undercarriage, but I have been spraying the wool wax on a couple times a year for a few years now, including inside the frame.

 

[JonMopar]

^ good advice

as far as 1 step paints go, chassis saver is about the best. If it’s going to see winter, regardless of what you paint it with, undercoat it (and not with that rubber crap).