1. Tight corner braking phenomenon
When the propeller shaft between the front and rear axles is connected directly, the differences between the rotations of the front and rear axles cannot be absorbed. This causes undue force to be brought to bear on the drive train. On roads with low coefficients of friction, if any of the tires slips, the difference between the rotations of the front and rear axles can be absorbed, but on roads with high coefficients of friction, such as dry paved roads, it is difficult for slipping to occur, creating a condition very similar to braking. This is called the “tight corner braking phenomenon”.
2. Weight is increased
The number of parts increases, so the weight increases.
3. Cost is increased
The more complex construction and the increased number of parts result in an increases in the cost of the vehicle.
4. Construction is complex
A transfer and propeller shaft, differential, etc., are required in order to distribute power to the front and rear wheels, making the construction complex.
5. Sources of vibration and noise increase
The increase in the number of rotating parts (transfer, propeller shaft, etc.) causes an increase in the number of possible sources of vibration and noise.