有一台经过维修保养的东方红—75型拖拉机在试车时,其它档都能正常工作,唯独挂Ⅲ档时拖拉机没劲,但发动机运转得却很轻松,并无超负荷现象。据了解,去年该机曾出现过类似现象,所不同的是,去年的故障出在Ⅱ档。经检查后发现,离合器踏板没有回到自由状态,而处在30～40毫米的有效行程处。于是,我们又卸下联锁轴垂臂上的拉杆,重新挂上Ⅲ档后,离合器能回到自由位置,拖拉机亦能正常行驶了。进一步检查后发现,拉杆后端与摇臂上安装孔之间相差约15毫米,联锁轴被卡住了,不能自由转动。可以肯定,故障出在变速箱锁定机构。卸下变速杆座后,真相大白,原来是框板的方向搞错了,即把V档 There is a maintenance of the Dongfanghong -75 tractor in the test, the other files can work normally, except when the third gear hanging tractors boring, but the engine is running very relaxed, there is no overload phenomenon. It is understood that last year the aircraft had a similar phenomenon, the difference is that the fault last year in the second file. After inspection found that the clutch pedal did not return to the free state, but at the effective stroke of 30 to 40 mm. So, we also remove the rod hanging arm interlock shaft, re hung up Ⅲ file, the clutch can return to the free position, the tractor can travel normally. After further inspection, it was found that the difference between the rear end of the pull rod and the mounting hole on the rocker arm was about 15 mm, the interlocking shaft was stuck and could not be rotated freely. To be sure, the fault lies in the gearbox lock mechanism. Remove the gear lever seat, the truth, turned out to be the direction of the framed wrong, that the V file