What's the reason for the failure of high and low gear shifting?

[DiLola]

Reasons for the failure of high and low gear shifting in vehicle transmission: failure of the high and low gear shift switch (pre-selection valve); incomplete clutch disengagement; air leakage or failure of the transmission dual H valve; failure of the transmission auxiliary box. Water in the air pipe can damage the precision components inside the H valve and also cause the synchronizer cylinder sealing ring to become stiff with excessive resistance. It is recommended to replace the H valve or cylinder sealing ring, as well as the high and low speed shift handle, and regularly replace the dryer. Relevant information is as follows: 1. High and low speed gears of vehicle transmission: also often referred to as: fast and slow gears, high speed gear, low speed gear. 2. Failure to shift between high and low speed gears in vehicle transmission: also often referred to as: inability to switch between high and low speeds, inability to shift from high to low speed, inability to shift from low to high speed, lack of high and low gears, etc.