189 

 

No. 140 No forward gear   

Malfunction Causes 

Solution 

Forward gear clutch malfunction 

1. Check oil pressure of drive gear, which shall be within standard 
value. If oil pressure too low, check whether oil pressure valve is 
jammed, and clutch oil plug is damaged; 
2. Check clutch friction disk is excessively worn;   

Forward gear brake malfunction

1. Check drive-gear clutch oil pressure; 
2. Check drive-gear brake friction disk is excessively worn; 
3. Check brake driving piston is jammed;   

Forward gear one-way clutch 
malfunction 

Check one-way clutch is damaged, and functionally abnormal;   

Control valve malfunction 

Check valve body of control valve plate is worn, leaking or blocked; 
if abnormal, clean, adjust or replace valve plate assembly.   

No forward gear 

Governing valve malfunction 

Check governing valve is blocked, worn or leaking; if abnormal, 
adjust or replace governing valve assembly;   

 

Governing valve 

Replace 

No forward gear 

Forward gear clutch 

Forward gear brake 

Forward gear one-way clutch 

Control valve 

Replace 

Replace 

Replace 

Replace 

Normal 

Unusual 

Normal 

Normal 

Normal 

Unusual 

Abnormal 

Abnormal 

Abnormal 

 
 

 

 

190 

 

No. 141 Transmission oil easily deteriorate   

Malfunction Causes 

Solution 

Transmission oil quality problem   

Transmission must be filled with qualified gear oil (degree 
of API GL-4, SAE 80W-85 viscosity); 

Transmission oil severely insufficient   

Oil level flush with lower plane of oil filler bolt; quality of 
gear oil not good, and its quantity severely insufficient, 
causing poor heat emission and excessive wearing of the 
bearing. Mating surface of constant meshing gear falls out 
due to high temperature causing transmission oil turning 
black and deteriorating; replace damaged parts and 
components and clean transmission, and replace gear oil; 

Transmission vent hole falls out 

Vent hole falls out, causing entry of dust and moisture 
from the atmosphere, and turning transmission oil white or 
dirty;  

Transmission inner malfunction 

Check meshing clearance of each gear pair within 
transmission is too small, which shall be between 
0.1-0.35. If too small, it will cause transmission oil 
temperature too high, thus facilitating gear oil 
deteriorating;  

Transmission oil 
easily deteriorate 

Gear oil not replaced according to specified 
time for a long time causing too much oil 
sludge, and oil easily deteriorates   

Disassemble transmission, and remove oil sludge and 
foreign substance. Clean scraps on the gear and bearing 
thoroughly. Refill gear oil with specified model, and 
replace it according to specified time and mileage.   

 

 
 

 

 

191 

 

No. 142 Auto transmission oil easily deteriorate   

Malfunction Causes 

Solution 

 

Transmission oil quality and quantity problem 

Auto transmission must be filled with qualified ATF 
(degree of DEXRON  or  DEXRON  ). Oil level shall 

Ⅱ

Ⅲ

be between the third or fourth hole of dipstick;   

Torque converter inner malfunction 

Replace torque converter assembly;   

Transmission inner malfunction 

Check ablation of each clutch and brake within auto 
transmission, making auto transmission oil deteriorate; 
replace clutch and brake friction disk;   

Auto transmission 
oil easily 
deteriorate 

Auto transmission heat-removal system 
malfunction 

Check heat-removal oil tank of auto transmission leaks, 
and there shall be no auto transmission oil within water 
tank; if any, replace radiator assembly; check 
heat-removal control valve is jammed, making 
transmission oil unable to remove heat circularly. Too high 
oil temperature will cause easy deterioration;   

 

Transmission inner malfunction 

Transmission oil easily deteriorate 

Transmission oil quality problem 

Transmission oil severely insufficient

Transmission vent hole falls out 

Refill accordingly 

Refill accordingly 

Repair transmission 

Repair 

Gear oil not replaced according to 
specified time 

Replace oil 

Normal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Normal 

Normal 

Normal 

Normal 

 
 

 

 

192 

 

No. 143 No reversing gear   

Malfunction Causes 

Solution 

Shifting operation mechanism incorrectly 
adjusted 

Adjust shifting operation mechanism (gear shifting lever or shift 
tie-line); 

Reversing locking mechanism worn, 
damaged 

Check reversing shift fork is severely worn, or fails; if abnormal, 
replace swing link support;   

No reversing 
gear, reversing 
not possible or 
automatic 
jump-out while 
reversing  

Reverse gear malfunction   

Check reverse gear ruptures or fails; if abnormal, replace gear; 

 

Transmission oil easily 

deteriorate 

Transmission oil quality problem 

Torque converter inner 

Transmission inner 

Auto transmission heat-removal 

system 

Replace 

Replace 

Repair 

Repaiar or replace 

Normal 

Abnormal 

Normal 

Normal 

Normal 

Abnormal 

Abnormal 

Abnormal