205 

 

No. 153 Chug sound in transmission case at idling speed   

Malfunction Causes 

Solution 

Clutch malfunction 

Clearance between hub and torsional spring within clutch friction 
disk is too large. Concentricity of transmission one shaft and 
engine crankshaft is out of true. Clutch friction disk and hub bent 
and deformed, and rotated causing abnormal sound. Connecting 
plane of transmission and engine shall be adjusted with adjusting 
pad;  

Transmission malfunction 

Bearing within transmission is excessively worn; clearance 
driving and driven gear of first, second gear is too large. Meshing 
clearance at 0.1-0.15; adjusting pad of output shaft is broken, 
making output shaft move forward; first gear scratches and 
differential generating abnormal sound;   

Chug sound in 
transmission 
case at iding 
speed 

Lubricating oil malfunction 

Check lubricating oil is poor or deteriorating. If abnormal, 
supplement or replace lubricating oil;   

 

Hiss sound when second, third, fourth gear upshift 

Second, third, fourth gear synchronizing ring 

Second, third, fourth gear 

Repaiar or replace 

Repaiar or replace 

Normal 

Abnormal 

Abnormal 

Chug sound in transmission case at iding 

speed 

Check clutch 

Check transmission 

Check transmission lubricating oil 

Repair 

Repair 

Fill or replace 

Normal 

Abnormal 

Normal 

Unusual 

Abnormal 

 
 

 

 

206 

No. 154 Da-da sound in transmission at idling speed   

Malfunction Causes 

Solution 

Clutch malfunction 

Gap between spline hub and one shaft spline within clutch 
friction disk is too large; replace clutch friction disk and one 
shaft;  

Transmission inner malfunction 

Check bearing ball of input shaft is crushed; tooth of 
driving and driven gear of first, second gear of input shaft 
is fallen individually; chamfer of reversing middle wheel 
and second-gear driving and driven gear is too small, 
making reversing gear scratch second-gear driving and 
driven gear; grind chamfer to make larger, and push 
reversing gear to the highest position with hands, making it 
not scratch second-gear driving and driven gear; check 
whether reversing gear and transmission housing collide; if 
abnormal, repair transmission housing. Check swing link 
support is loosening, causing reversing gear collide with 
transmission housing; if abnormal, replace support;   

Da-da sound in 
transmission at 
idling speed 

Lubricating oil malfunction   

check lubricating oil is insufficient; if not sufficient, fill up; 

 

 
 

 

 

207 

 

Da-da sound in transmission at idling speed 

Check clutch 

Check transmission 

Check transmission lubricating oil 

Repair 

Repair 

Add or replace 

Abnormal 

Normal 

Normal 

Abnormal 

Unusual 

 
 

 

 

208 

 

No. 155 Buzz sound during driving at high speed   

Malfunction Causes 

Solution 

Viscosity of transmission oil too small, quantity too 
little 

Check viscosity of transmission oil is too small, and 
quantity is too little. Fill in API   GL-4 SAE 80W-85 
and oil level is flush with lower plane of oil filler; 

Tightening torque at connection of transmission 
lever 

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; 

Meshing mark of differential gear ring and output 
shaft abnormal, and differential bearing worn   

Mainly check meshing mark of differential gear ring and 
output shaft, which is adjusted between 0.1-0.15mm. 
Meshing mark shall be in middle of tooth, with area no 
less than 80%. Meshing point not falling out; differential 
bearing worn or loosening. Ball, track within bearing 
not falling out. Inner and outer cover not obviously 
loosening while shaking bearing.   

Transmission cone bearing incorrectly adjusted 

check cone bearing is adjusted too tighten; if not 
normal, adjust and check differential;   

Buzz sound during 
driving at high 
speed 

Transmission synchronizer malfunction 

 Toothed ring of synchronizer is excessively worn. 

①
Clearance on the gear pressed by synchronizer ring is 
no less than 0.5mm. Specified value is between 
0.85-1.45. Area of joint face of fifth-gear synchronizing 
ring and gear shall be larger than 80%; if lower, replace 
synchronizing ring;   

 

②

Check fit clearance of hub, cover, which shall be no 

obvious clearance while shaking from left to right. Hub 
shall be assembled within the cover freely. Joint part of 
cover and gear shall be triangular. Replace 
synchronizer assembly if damaged, worn, or its edge 
angle turning round; 

 Check height of slide block of synchronizer; if less 

③
than 5mm, replace slide block;