My Truck
 

This is the truck that is currently getting me about 18mpg. It's got a very loose auto-tranny with a lockup torque converter that doesn't kick in until about 50mph.

http://i7.photobucket.com/albums/y26.../Retard001.jpg

There is a headache rack that sticks above the roof by about 4in, and has a metal screen that is difficult to see in the picture. What difference do you think lowering this below the roof line will make for highway fuel economy at 60mph? I've also considered a grill block to get temps up faster and improve aero.

All of this might be for nothing though, as I may sell it and buy my grandpa's '03 Chevy S10.

http://i7.photobucket.com/albums/y26...kes/truck2.jpg

Don't expect any better from the S-10.

unless that s10 happens to have a 5speed manual its the rong kind of s10 to get better mileage in. being that model s10 itll be tougher to get better mileage being the offroad style

What year is your truck? What engine does it have?

I have found that using OD OFF will save a bit of gas on my truck, if I am driving in town and know that I am not going to get up to above 45 MPH.

^^HA! I love the aero cat GIF.

Chop and lower the bar, use it as a pivot for an openable BZP-style aero shell. That's got to guarantee you at least 2MPG. In fact, just read BZP's thread and copy all his mods :D

Also, if you can lower it and use street tires...

No doubt the S10 will likely get worse mpg, but it has low miles on it and grandpa wants to buy a new Tacoma and sell this to me cheep. I can't justify 2 trucks, a Jeep, a car and a motorcycle. Jeep and one of the trucks has got to go.

Year 1998.5
5.9L Cummins turbo diesel (electric fuel pump)
3.55 rear axle ratio

I'll have to try the OD off trick. Perhaps I can find a way to wire up a TC lock switch.

The tranny is tired though, and I just can't see putting $2-3k into it. Speedo stopped working, and I think that causes the grid heater to stay on longer than it needs to.

I like this idea, except I went the other direction on tires. 285/75-R16. I made that tire decision back when I was paying $1/gal for reclaimed fuel.

Here are the tires I'm using currently.
http://i7.photobucket.com/albums/y26...-57-31_501.jpg

I doubt changing the rack will do much of anything measurable. As far as the grille block goes, here's how I did it:
http://ecomodder.com/forum/showthrea...wer-19810.html

Just do a little re-shaping on that brush, throw a tarp over it and you've got an aero cap :D

What MPG improvement did you see from the grill block?

As you can imagine, the load acted as the opposite of an aerocap. The wind resistance was tremendous, and I drove about 50mph for my 70 mile trip. It was early morning and the State Patrol would observe me a while before deciding not to pull me over. Still, I averaged 18mpg overall for that tank.

http://i7.photobucket.com/albums/y26...-57-50_733.jpg

I never really quantified the mpg improvement from the grille block. I did it in several stages, and the weather was changing all the time. My best guess would be around 5% improvement.

Dodge / Chevy
 

The 1st gen S-10/GMC S-15 was Cd 0.475 and with mild streamlining (Gale Banks Syclone ) got down to Cd 0.315 which was lower than a Corvette at the time.
Your grandad's S-10,in 2WD configuration is Cd 0.42,a much cleaner starting point.
If this lower drag,smaller frontal area,lighter truck can handle your hauling and pulling duties,then it would have better 'beginning' parametrics than the Dodge.
With a comprehensive streamlining package you could drop below Cd 0.2.
This would get you easily above 30 mpg,based on early powertrains.

The S-10 is a 4.3L 6 cylinder 4x4 with off road package and a medium aggressive tread pattern. It's rated at 14/18 15mpg combined with the automatic tranny.

My full size turbo diesel easily gets better fuel economy even with a full load. I like the Dodge better because I have pulled heavy with it before, I can crash through the forest without caring about dents, and it has bench seating. The downside is it has 350,000 miles on it, the brakes suck, the AC is out, the speedo and cruise stopped working, and the front end is perpetually sloppy. Oh, and it needs a tranny rebuild.

I suspect the only reason the Chevy doesn't have more problems is that it only has 60k miles on it.

I've thought about a bed topper for either truck, but I only drive the thing when I'm hauling something.

Brakes are fairly easy to overhaul on a Dodge.

It sounds like you lost a vehicle speed sensor, first of all. The speedo and cruise control rely on this sensor to figure out how fast the truck is going. Odds are that your transmission is sloppy, for the same reason. No vehicle speed sensor = no way the powertrain computer would know when to lock the torque converter up.

However, if your transmission problem is separate from your lack of a vehicle speed sensor, you might could try to find a replacement transmission from a junkyard, instead of paying the $2000 or so to overhaul yours.

Thanks for the reply T Vago. I've replaced the calipers already once, but they just don't seem to like to work for very long. Truck always pulls when under heavy braking. This is the least of my worries at the moment.

I don't know if the speed sensor thing is just a broken wire, or if my tone ring is too damaged for it to work. You see, I had a few bolts let loose in my differential and it did a little damage to my tone ring, which is read by the speed sensor. My guess is a bad connection somewhere. The tranny is bad separate from the sensor issue, but a junkyard pull is a thought. These trucks are notorious for bad trannys though, so I'm hesitant to pull one.

Here you can see a sheared bolt that came almost entirely out, and damaged teeth on the tone ring.
http://i7.photobucket.com/albums/y26...m/P2210085.jpg

More bolts just sitting in the differential housing.
http://i7.photobucket.com/albums/y26...m/P2210086.jpg

That tone ring looks shot.

Understand the hesitation about getting a replacement tranny. Maybe it's time to do a 5-speed conversion! Heh.