Fool's Errand (Aeromodding GMC 2500HD)

[vskid3]

Got part of the front pan done today. I cranked the wheels to one side and realized I couldn't go back very far before the tire would hit. I decided to split it into 3 sections, the middle (the width between the lower control arms) and the two sides in front of the wheels. I did the middle today because it can go back pretty far and it happened to be the same width as the left over coroplast from the passenger running board.

Took it for a test drive that included a few miles of 60MPH freeway and everything survived.






If anyone is curious how I go about sizing and installing the belly pan pieces, here's a quick rundown. First I figure out what area I want the piece to cover. Sounds obvious, but there are many things to consider such as how far the wheels move when turned, suspension travel, and accessibility for maintenance (I stopped this piece before the oil drain and filter). I then get a rough measurement of the area and cut the coroplast. Good ol' fashioned trial and error is used to get the piece cut to fit correctly, so lots of trips under the car.

For the zip tie locations, I look for existing holes or brackets I can loop over. You may have to add some framework. I measure and mark them on the coroplast like plotting points on a graph (over 6", up 12"). To make the holes I use a utility knife to cut one side, making sure it's oriented correctly, stick a small flat-head screwdriver through to open the hole, and press down to mark the other side. Then I flip the piece, cut through the marks, and use the screwdriver to open them. This gives me holes that are just big enough for the zip ties and avoid cutting the flutes.

To mount the piece of Ecomodder art, start at one edge and put its zip ties though. I started with the bumper lip and running board lips edge. I don't necessarily start zipping them, the just-big-enough holes grip the tie quite well and allow me to remove them if I need to later in the process. Then I work my way from that edge to the opposite edge, sticking zip ties up, wrapping them through the hole or around the designated holding object, and back through the coroplast. When all the ties are in their proper places, I begin zipping them a little bit at a time until they're as tight as they need to be. I used 8" and 11" UV resistant zip ties, occasionally doubling them up for additional length.

Here's a picture from halfway through the mounting process. None of the shown zip ties are zipped yet, it's just the bumper lip at the front and the tails of the two middle zip ties holding it up.




I'm done with working on the truck for the weekend, sliding around under the truck gets old after a while. The next things will be the sides of the front and the bottom of the control arms. I'll also start experimenting with the partial bed cover (then I don't have to lay under the truck).

[elhigh]

Your treatment of the running boards was exactly what I was going to suggest.

I had no idea the front wheels would intrude as far as that under the truck when turning.

The front pans really looks the business. Looking forward to the next Fuelly update!

[ijames]

I have the same shape truck, 2005 2500HD extended cab short bed, but Duramax diesel 2wd 5 speed allison auto. Logging about 100k miles on the highway I got about 22 mpg at 60 mph and then lost about 2 mpg for each 5 mph above that, so 20 at 65, 18 at 70, and 16ish at 75. I looked at the GM tonneau patent and decided that 44% was about the optimum and a convenient size so I could still reach into the bed with the cover on. Built it from plywood with a 2x4 frame so two big guys could sit on it in chairs. It is held down with ratchet straps and 1/4" line to the rear cargo hooks so it comes right out if needed, or I just lay it flat in the bed and put the cargo on top of it. It has never moved from wind, even on a short drive with the straps loose just to see. Here's a couple of pictures:





Did nothing below about 55 mph but added about 1.5 mpg at 60, 65, and 70 mph for sure, probably about the same at 75 and 80 but don't have good data. So basically it lets me drive almost 5 mph faster for the same mileage on the highway. It's been on for about a year and 15k miles so far with no issues. If you cut my plywood in half across the truck, added two more 2x4 cross pieces along the new edges, and then bolted them together with a couple of through bolts you would have the same thing for running empty but you could split it into two and lay each half out of the way down in the bed beside your 5th wheel hitch for towing. I bought some generic lug covers and pizza pans to make some wheel covers but never got around to that, and I was never ambitious enough to even consider your belly pan, but this was pretty simple.

[vskid3]

Nice cover, ijames! My dad has a 2002 2500HD crew cab, short bed with a Duramax and 4wd (I believe Allison tranny as well), he gets about 1MPG less than your stock numbers. He isn't interested in doing stuff like skirts and belly pan, but he likes your cover. It looks like it wouldn't be much trouble to add folding legs to it to make it pull double duty as a table.

I put a pan on the bottom of the lower control arm on the driver's side today. I have a picture of the bare passenger side for comparison. Passenger side is cut out, just needs installed.




Took another trip to Home Depot, averaged 15.7MPG compared to 16.5 for the coroplast trip. Traffic was pretty bad (El Paso drivers are terrrrible), got stuck at a couple lights, and had AC on for the return leg, so really not that bad. Tank MPG so far is looking a bit better than I would usually expect.

My wife has banned me from doing any more aeromods til I fix the climate control. It blows hot air out of the passenger side (dual zone system) regardless of the settings. This results in warm air seeping through the closed vents and the driver's side air being shared, which is why the AC was needed on today's trip. Pretty sure it's a bad blend door, only need to take apart most of the dash to get to it...

[ijames]

Thanks for the kind words, vskid3. You could add legs to make it a table, or sit on the tailgate with your legs under the cover as a quickie picnic table, and it's just long enough to be a very steep ramp from ground to tailgate if you need to partly slide and/or partly roll something up into the bed that you just can't quite lift by yourself :-). That 1 or so mpg difference between your dad's truck and mine is why I searched so long and hard for a nice 2 wd truck instead of settling for a 4 wd that I would only use in 4 wd maybe once a decade (automakers don't have to do the epa mpg test on 3/4 ton trucks but from all the 1/2 ton data I expected 1-2 mpg better).

[darcane]

Originally Posted by vskid3

My wife has banned me from doing any more aeromods til I fix the climate control. It blows hot air out of the passenger side (dual zone system) regardless of the settings. This results in warm air seeping through the closed vents and the driver's side air being shared, which is why the AC was needed on today's trip. Pretty sure it's a bad blend door, only need to take apart most of the dash to get to it...

When you adjust the temperature settings on the climate control, do you hear a clicking sound under the dash? That's usually the telltale sign of the blend doors failing. I need to do it on our Tahoe and I'm not looking forward to it.

[LousMX5]

I've got the 2005 diesel version of that truck, watching with great interest!
You can remove those flares and likely get a little more aero advantage, likely only a little rubbing underneath that could have corrected with a little polishing compound.

Best of luck!

[vskid3]

I finally got the climate control situation figured out. Took the dash apart to get to the passenger side blend door actuator, it was toast. Went to Autozone and got the cheapest actuator, only had 3 pins instead of 5 like the old one, must be a redesign, I think to myself. Didn't work, so I figured it must be the control unit (part with the knobs and slides). Finally got that in, still no go. Realize I'd messed up the zeroing of the driver's actuator (which was good to start and used as my tester). Fixed that and it worked on the passenger door as well. Figured out that the new actuator was the wrong one, take it back and get the right one (not quite the cheapest) with 5 pins. And it works. So the controller might not have been bad, but I'll keep the new one because I already turned in the core ($200!?!). Now I just have to put the dash all back together and it should be good as new.

While waiting for parts to arrive, I put the pan on the passenger side lower control arm. No pics because it's the same as the driver's side. I think I'll finish the sides of the front pan and plug some holes in the front bumper next.

[vskid3]

Painted the wheel skirts black because I was painting something else. Looks much better than the white. I'll Plastidip the metal black, for easier clean up.

[darcane]

Originally Posted by vskid3

I finally got the climate control situation figured out. Took the dash apart to get to the passenger side blend door actuator, it was toast. Went to Autozone and got the cheapest actuator, only had 3 pins instead of 5 like the old one, must be a redesign, I think to myself. Didn't work, so I figured it must be the control unit (part with the knobs and slides). Finally got that in, still no go. Realize I'd messed up the zeroing of the driver's actuator (which was good to start and used as my tester). Fixed that and it worked on the passenger door as well. Figured out that the new actuator was the wrong one, take it back and get the right one (not quite the cheapest) with 5 pins. And it works. So the controller might not have been bad, but I'll keep the new one because I already turned in the core ($200!?!). Now I just have to put the dash all back together and it should be good as new.

While waiting for parts to arrive, I put the pan on the passenger side lower control arm. No pics because it's the same as the driver's side. I think I'll finish the sides of the front pan and plug some holes in the front bumper next.

So, how bad of a job was this? Other than getting the wrong parts at least. How long did it take?