I've replaced the full-time transfer case in my WJ with a part-time one from a KJ, which allows me to run in 2wd mode and the entire crossmember and transfer case are now tucked in higher (40mm) for better off-road clearance. That might also help with aero drag under the car.
Stock:
Now:
The stock transfer case had way more "drag" between the front and rear output flanges than I imagined and the fuel consumption data is interesting:
Average fuel consumption (city, two-lane roads, some light offroading), with airdam, street tires and standard transfer case, over 750 miles:
21.09 MPG
Average fuel consumption (including about 50 miles of offoading), with the new transfer case, 32 inch mud tires, no airdam and chopped bumper, over 300 miles:
21.22 MPG
If I account for the tire size difference, which is 9.3%, it would mean I traveled more than what the odometer reads, which brings the fuel consumption to
22.55 MPG
That looks like there were some solid gains from the transfer case swap, enough to offset the aero differences and drag differences from the mud tires, or am I interpreting this wrong?
Mud tires vs street tires:
