The driveshaft is a crucial component of a four-wheel-drive or all-wheel-drive vehicle's drivetrain. Removing it will:
* Disable 4WD/AWD: The most immediate consequence is that your vehicle will lose its all-wheel-drive or four-wheel-drive capability. This means you'll only have two-wheel drive, but it might still be engaged in AWD/4WD mode depending on your vehicle's system and may even result in damage to the transfer case.
* Potential for Drivetrain Damage: Depending on your vehicle's system, removing the driveshaft could lead to damage to the differential, transmission, or transfer case. These components are designed to work together; removing the driveshaft upsets this balance, potentially causing significant and expensive repairs.
* Unsafe Operation: Loss of 4WD/AWD capabilities can dramatically reduce traction, especially in slippery conditions like snow, ice, or mud. This makes the vehicle significantly less safe to operate.
* Dashboard Warning Lights: Your vehicle will likely display warning lights on your dashboard indicating a problem with the drivetrain.
In short, removing the driveshaft for better gas mileage is a very bad idea. It's far more effective and safe to improve gas mileage through other methods, such as proper tire inflation, regular maintenance, and driving efficiently.
