Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - 4x4 mech drag - transfer cases (esp double), manual vs auto hubs, axles, etc.

wjohn · 08-24-2014, 05:57 PM

This is pretty anecdotal but it's about all I can contribute. My '90 Dodge Dakota 2WD V6 auto with 3.21 rear gears and 8' bed usually got 21-23 MPG on the highway. Curb weight is a little over 3,000 pounds and it had 205 mm wide tires.

I was a little apprehensive when I got my current Dakota because it's a 4WD. It is also a '90 with the V6 and 8' bed. It does however have a manual transmission, which should yield better fuel economy. On the flip side it's a couple inches taller, has 3.55 gears and 235 mm wide tires, and weighs 700 pounds more (curb weight around 3725 lbs.). About 400 pounds of that is the difference from 2 to 4WD and the remainder is due to the heavy-duty payload package.

I only had a chance to run one tank in the 4WD before I tore it apart to fix some things. I was pleased to average 21.5 MPG on a tank of very mixed highway/city/dirt road driving. That was with a very worn timing chain, slightly dragging calipers, and wheels that stick out past the side of the vehicle. I'm sure it'll do better than that when I finish working on it and get a chance to do some highway cruising.

The old EPA ratings showed 21 MPG on the highway for the 2WD auto and 19 MPG highway for the 4WD manual (a 2WD manual is rated at 22 MPG highway). Anyway, I would need to test a truck that's identical to my 4WD minus the 4WD for a real one-on-one comparison, but I guess I was just excited to see over 20 MPG right off the bat. I've never owned a 4WD truck before.

This truck has a center axle disconnect instead of locking hubs so the front differential is still turning (but "open" - the right axle shaft gets split by the disconnect). The front driveshaft and transfer case chain drive are not turning.

08-24-2014, 05:57 PM	#4 (permalink)
wjohn EcoModding Lurker Join Date: Apr 2014 Location: KS Posts: 15 Hatchback - '90 Honda Civic DX 90 day: 44.98 mpg (US) GTS - '90 Dodge Dakota 4WD Base 90 day: 18.34 mpg (US) Topless Brick - '66 MG MGB Roadster 90 day: 27.19 mpg (US) Sedan - '91 Honda Civic DX 90 day: 41.74 mpg (US) Thanks: 1 Thanked 4 Times in 4 Posts	This is pretty anecdotal but it's about all I can contribute. My '90 Dodge Dakota 2WD V6 auto with 3.21 rear gears and 8' bed usually got 21-23 MPG on the highway. Curb weight is a little over 3,000 pounds and it had 205 mm wide tires. I was a little apprehensive when I got my current Dakota because it's a 4WD. It is also a '90 with the V6 and 8' bed. It does however have a manual transmission, which should yield better fuel economy. On the flip side it's a couple inches taller, has 3.55 gears and 235 mm wide tires, and weighs 700 pounds more (curb weight around 3725 lbs.). About 400 pounds of that is the difference from 2 to 4WD and the remainder is due to the heavy-duty payload package. I only had a chance to run one tank in the 4WD before I tore it apart to fix some things. I was pleased to average 21.5 MPG on a tank of very mixed highway/city/dirt road driving. That was with a very worn timing chain, slightly dragging calipers, and wheels that stick out past the side of the vehicle. I'm sure it'll do better than that when I finish working on it and get a chance to do some highway cruising. The old EPA ratings showed 21 MPG on the highway for the 2WD auto and 19 MPG highway for the 4WD manual (a 2WD manual is rated at 22 MPG highway). Anyway, I would need to test a truck that's identical to my 4WD minus the 4WD for a real one-on-one comparison, but I guess I was just excited to see over 20 MPG right off the bat. I've never owned a 4WD truck before. This truck has a center axle disconnect instead of locking hubs so the front differential is still turning (but "open" - the right axle shaft gets split by the disconnect). The front driveshaft and transfer case chain drive are not turning.