201 

 

 

No. 150 Hiss sound when put into gear during driving   

Malfunction Causes 

Solution 

Gear shifting lever malfunction   

Check tightening torque at connections of gear 
shifting lever and transmission is too tightening, and 
rubber cover is not isolating vibration, making sound 
introduced to cab; 

Fourth-gear shift shaft and fork malfunction 

Check working face of fourth-gear shift shaft and 
fork is vertical; if not, replace fourth-gear fork. Check 
working face of fork is worn unilaterally; if so, replace 
fourth-gear fork;   

Hiss sound when 
put into gear 
during driving 

Fourth-gear synchronizer malfunction   

 Check fourth

②

-gear synchronizer spring and ring 

are damaged; if conical surface turns small or 
deformed, replace synchronizer toothed ring; 

 

Fifth gear, first gear blocks, relieved only when the vehivle 
stops 

Check gear shifting lever 

Clutch not fully separated 

Transmission inner malfunction 

Repair 

Replace 

Repair 

Abnormal 

Normal 

Abnormal 

Abnormal 

Normal 

 
 

 

 

202 

 

Hiss sound when put into gear during 

driving 

Check shift bar 

Fourth-gear shift shaft and fork 

Check fourth-gear synchronizer 

Replace 

Repair 

Replace 

Abnormal 

Normal 

Abnormal 

Abnormal 

Normal 

 
 

 

 

203 

 

No. 151 Transmission gear runout   

Malfunction  

Causes 

Solution  

Fixed bolt of transmission 
loosens  

Check fixed bolt of transmission; fasten it if loosening;   

Gear shifting lever deforms   

Gear shifting lever deformed causing gear abnormally or not well jointed; 

Shift fork within transmission is 
excessively worn, self-locked 
spring breaks or too softens; 
replace self-locked spring and 
fork 

1. If gear runout found at any gear, gear lever is switched to this gear, 
then remove transmission cover and check gear meshing; if normal, 
check locking mechanism of shift fork shaft; 
2. Push positioning device of shifting fork with hands; if poor, remove shift 
fork shaft and check positioning ball and spring; if the spring is too soft or 
broken, replace it. If groove of shift fork shaft is excessively worn, repair 
or replace it; 
3. Check screws of fixing plate of shifting fork are loosening, and 
clearance between fork end and gear groove is too large; correct it if 
shifting fork bends; if lower end of shifting fork is worn and sliding gear 
groove is too loosening, remove and repair it; 

Axle head of swing link support 
within transmission is 
excessively worn, making all 
gears not well positioned   

Weld up shaft end of swing link support, and grind it to stand dimension; 

Bearing and shaft unusually 
worn 

Check abrasion of bearing and shaft; if the shaft is severely worn, bearing 
is loosening or shift shaft plays axially, then remove, repair or replace;   

Spline clearance between 
transmission clutch collar and 
spline hub too large; clearance 
between clutch collar and tooth 
of put gear too large   

Check operation of synchronizer; if malfunction found, repair or replace it; 

During driving, 
gear lever 
automatically 
jumps to neutral 
position, which 
may occur when 
driving at medium, 
high speed, load 
suddenly changes 
or automotive is 
vibrating severely, 
and most trip stop 
during at high 
speed. 

Soldered tooth bent or deformed, 
abrasion smaller   

Check meshing of gear; if not fully meshed, check gear is worn or in 
taper; replace it if severely worn;   

 

 
 

 

 

204 

 

No. 152 Hiss sound when second, third, fourth gear upshift   

Malfunction Causes 

Solution 

Second, third, fourth gear synchronizing ring 
malfunction  

check back clearance of synchronizing ring of second, third, 
fourth gear is not proper; if not normal, check end face of 
synchronizing ring is excessively worn; if abnormal, replace 
synchronizing ring; 

Hiss sound when 
second, third, 
fourth gear upshift 

 
Second, third, fourth gear malfunction 

Contact face of gear end face and synchronizing ring is 
excessively worn; if abnormal, replace gear; 

 

Transmission gear runout 

Fixed bolt of transmission loosens 

Shift fork within transmission worn 

Swing link support within transmission 

Unusual abrasion of bearing and shaft 

Synchronizer clutch collar and spline hub 

Replace 

Replace 

Replace 

Repair 

Soldered tooth bent, deformed, worn 

Replace 

Fasten 

Abnormal 

Normal 

Normal 

Normal 

Normal 

Normal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Abnormal