[wmjinman]

Ok, so yeah - try to build a deflector. But please do "A-B-A testing" with your ScanGauge. Otherwise, it'll be VERY difficult to determine for sure if it's working at all. Read MetroMPG's guide on A-B-A testing under the "EcoModding Central" area. That method works really well, and will tell you for sure if your mod is "working" or not. If you get "inconclusive results", and you're testing it correctly, then it's not helping enough to matter.

I think a 1/8th inch steel belly pan would be too heavy (and trouble to make)to be worthwhile. If you're going to do it, use something lighter (thinner sheetmetal, aluminum, composite, - - -). A simpler approach might be to do an air dam. Does your truck have a factory air dam, and if so, does it extend far enough down that it's as low as all of the other "junk" hanging down (differentials, etc)? If not, building an air dam, or extending it, down to where it's as low as the lowest hanging stuff underneath will help a lot. While you're at it, try to contour the sides so they also deflect the air around the front tires. You would probably get more "bang for the buck" with this than a 1/8" steel belly pan.

From what I pick up on here, grille openings are designed oversize so there's enough air for ANY occasion (I read that to mean towing an Airstream trailer up the mountains out of Death Valley in the summertime with the A/C on!!!) So, there is certainly an opportunity to block your grille some (probably over 50%) without hurting your temp. (unless you're pulling aforesaid trailer out of Death Valley in the summer). You can set your ScanGauge to read water temp, and when fooling around with grille blocking, it's highly recommended to do that & monitor it closely. On my 2000 Jimmy (4.3 liter, auto tranny, 4wd), I think I picked up 1.4 MPG by blocking the grille. At first, I blocked it all the way, and it DID overheat. So I cut a hole in it (just used cardboard to experiment) and that helped. Later on, I decided to enlarge the hole (to 6.25" diameter), and that did the trick - no more overheating after that. Likewise, if you're not too worried about it looking too "Jethro redneck", why not experiment with cardboard & duct tape? Easy, effective, and will tell you the story in A-B-A testing with the ScanGauge.

If you click on the "Jimmy" under my name in the column on the left, you can see a picture of what I did.