Also pull the rear tail lights out and spray between the inner and outer panel. Soak it real good. As you mentioned, spray past the foam stuffer in the front wheel well as well.
Good idea.
In addition ...a guy can literally spray/sqirt oil by shooting it up from the front-side of the rear wheels. There's good access there. Unfortunately thats where a lot of the rocks debris and sand get into the rear wheel wells too.
I personally would recommend (and I know everyone who's never done the job is going to disagree with me here) ...but I would recommend
spraying a diluted mixture of oil over the rear wheel wells. Fluid film around the rest of the trucck. For the simple reason that oil is less viscous and will penetrate the pieces of metal better. Let's analyze what's going on over the ram wheel wells and I think you'll better understand. (see the cross-section of the inner/outer panels, illustration I made below).
#1. Sheet metal contours: You have the outer body sheet metal and an inner body sheet metal.
#2. There is a narrow gap between them in places...~ 1/8" Little rocks & stones love to get lodged in this region. They build up over time. I cleaned them out of my trucks wheel wells and got probably a cup of debris or more out of each side.
#3. Ram applied a sealant on the lip (seam) where the inner and outer panels meet, and THEN spot welded them together. That's going to block any oil from penetrating the lip, unless there's an imperfection in their sealant. A thinner product might find a way to the other side ...that's the "hope". Definitely fluid film won't.
#4. Fluid film and other similar products set up firm. That's not really what you want over the rear wheel wells to get 'drawn' pas the sealant between the upper area and the lip. Setting up firm is also going to 'catch & hold' any small stones or debris that bounced up into that gap in the upcoming years. That's my thought anyway. A thinner product will allow you to clean the stones & debris out in a couple years and re-oil.
#5. A few years down the road, you can spray and easily remove build-up debris from an oiled area, ..whereas the fluid film creates a nasty gooier mess. I guess if you look at it as a 5 year fix, the fluid film is ok. If you're looking at it as a 20 year job, use the oil, and re-apply periodically.
#6. You need to apply fluid/oil to BOTH SIDES of the inner and outer panels.
#7. You should park the truck on an angle overnight ...or 2 days...and squirt oil on the wheel SEAM and let gravity and capilary action draw oil INTO the seam overnight...or two days.
At the bare minimum, just shoot some oil from the gap at the front-side of rear wheels. You can do this w/o even removing the plastic inner fender liners (which is kind of a bugger by the way).
Good luck
