Cool... Rod did the math.
Seems the few gallons saved on even a long trip may not be even close to being worth the added expense, complexity, and labor. But I admit I've considered it too... but have since decided I'm not going to bother.
Another consideration regarding the AWD unit (if you intend to use it)... is that it has clutch preload. This means it DOES spin EVEN when not engaged. This is why it is important to have 4 matching tires while driving.. all on the ground and turning the same speed (hence the damaged caused by improper towing). Note the front tires STILL drive the system backwards (when not engaged), but it's all turning regardless.
The front shaft MUST spin at same rate as rear shaft.
Eliminate the front tires from turning the unit, and I wonder if the pre-load will STILL turn the output, or sufficiently enough to match so as not to burn up the clutch-packs. If you plan to utilize a true manual 4x4 transfer case.. then this part of the discussion no longer applies.
As mentioned.. aggressive tires are the real killer of MPG. I do 99.99% of my driving on road or the highway, and can count on my hand the number of times I've actually pulled it into 4WD for quick use... or needed this type tire. I also realize everyone's situation may be different. LT tires are a must... but I've also gone with an HT (highway touring) tire designed for lower rolling resistance which increased my fuel economy quite noticeably. Nice and smooth too. But yet I still have excellent 4x4 use, and it's an extremely rugged commercial 10 ply load range E tire that does well off-road too.
Just some more food for thought if you're looking for efficient fuel economy..
Seems the few gallons saved on even a long trip may not be even close to being worth the added expense, complexity, and labor. But I admit I've considered it too... but have since decided I'm not going to bother.
Another consideration regarding the AWD unit (if you intend to use it)... is that it has clutch preload. This means it DOES spin EVEN when not engaged. This is why it is important to have 4 matching tires while driving.. all on the ground and turning the same speed (hence the damaged caused by improper towing). Note the front tires STILL drive the system backwards (when not engaged), but it's all turning regardless.
The front shaft MUST spin at same rate as rear shaft.
Eliminate the front tires from turning the unit, and I wonder if the pre-load will STILL turn the output, or sufficiently enough to match so as not to burn up the clutch-packs. If you plan to utilize a true manual 4x4 transfer case.. then this part of the discussion no longer applies.
As mentioned.. aggressive tires are the real killer of MPG. I do 99.99% of my driving on road or the highway, and can count on my hand the number of times I've actually pulled it into 4WD for quick use... or needed this type tire. I also realize everyone's situation may be different. LT tires are a must... but I've also gone with an HT (highway touring) tire designed for lower rolling resistance which increased my fuel economy quite noticeably. Nice and smooth too. But yet I still have excellent 4x4 use, and it's an extremely rugged commercial 10 ply load range E tire that does well off-road too.
Just some more food for thought if you're looking for efficient fuel economy..
