1. If the mixer is a 9-gear truck with high and low gear transmission

高低档转换时，高低档的转换只能在低档的一个档位4和高档的个档位5之间进行。如果跳档操作，比如4转6，7转3之类的，副箱同步器因转速差较大，摩擦带会早起耗损。高档摩擦带摩秃了，低转高的瞬间就会听到咔咔咔的打齿声，反之亦然，这是因为同步器摩擦带失效后齿轮的同步工作靠同步器结合齿和低档减速齿轮或高档驱动齿轮的结合齿撞击结合所致。进而会造成上述齿轮的打齿，在进而会造成副箱脱档。

During high-low gear conversion, high-low gear conversion can only be carried out between the last gear 4 of low gear and the first gear 5 of high gear. In case of gear skipping operation, such as 4 to 6, 7 to 3, the friction belt will get up early and wear out due to the large speed difference of the auxiliary box synchronizer. When the high-grade friction belt rubs bald, the clicking sound will be heard at the moment of turning low to high, and vice versa. This is because the synchronous work of the gear after the failure of the synchronizer friction belt is caused by the impact combination of the synchronizer coupling teeth and the low-grade reduction gear or the high-grade drive gear. This will cause the above gear to beat, and then cause the auxiliary box to shift out.

高低档转换时，由一个档区的空档横拍另一档区的空挡后，必须有意识地稍停片刻（正常情况下1秒内），以保证副箱同步器的转换结合成功，一般以听到转换时同步器发出的啪声为准，然后再挂入你要转换的目标档位即可。如果副箱还没结合成功（野蛮换档、气路气压不稳、气路不畅等等因素），你就去挂主箱的档位，就有可能造成副箱同步器断销等故障，严重的还会造成副箱爆裂。

When switching between high and low gears, you must consciously pause for a moment (within 1 second under normal circumstances) after taking a horizontal shot from the neutral of one gear zone to the neutral of another gear zone, so as to ensure the successful conversion and combination of the auxiliary box synchronizer. Generally, it is subject to the sound of the synchronizer during the conversion, and then shift into the target gear you want to convert. If the auxiliary box is not combined successfully (brutal shift, unstable air pressure in the air circuit, poor air circuit, etc.), you go to the gear of the main box, which may cause faults such as broken pin of the synchronizer of the auxiliary box, and even burst the auxiliary box.

2、如果是单H操纵的变速箱

2. In the case of a single h-operated transmission

单H操纵的变速器档位只有一个空档，所有的低档和高档对应的档位都是重合位置，包括空档在内。因此它的高低档转换，无法靠横拍实现，而是靠驾驶室换档手球侧面的高低档扳钮向下向上拨动实现高低档的转换。向下为低档，向上为高档。单H阀，其实就是单路的气阀，气流通过推动换挡拨叉实现1.2.3.4档间转换。单H阀用于不带副箱的基础档位切换。

The transmission gear operated by single h has only one neutral, and all gears corresponding to low gear and high gear are coincident positions, including neutral. Therefore, its high-low gear conversion can not be realized by the horizontal racket, but by the high-low gear pull button on the side of the shift handball in the cab moving downward and upward to realize the high-low gear conversion. Down is low gear and up is high gear. The single h valve is actually a single-way air valve. The air flow realizes the shift between 1.2.3.4 gears by pushing the shift fork. Single h valve is used for basic gear switching without auxiliary box.

3、如果是双H操纵的变速箱

3. In the case of a dual h-operated transmission

双H阀是双路气阀，其中一路实现1.2.3.4档转换，另外一路通过副箱实现高速5.6.7.8档转换。双H阀主要用于带副箱实现高低档切换和基础档位切换。主箱和分动箱是分开的，主箱的换档动作和副箱的换档动作需要同时做，结合起来才是挂高速档，而这个需要双路气阀实现。

Double h valve is a two-way air valve, one of which realizes the shift of gear 1.2.3.4 and the other realizes the shift of high-speed gear 5.6.7.8 through the auxiliary box. Double h valve is mainly used to realize high-low gear switching and basic gear switching with auxiliary box. The main box and transfer box are separated. The shift action of the main box and the shift action of the auxiliary box need to be done at the same time. Only when combined can the high-speed gear be engaged, which needs a two-way air valve.