185 

 

Shifting valve 

Replace 

Repair 

Control valve plate 

Throttle tie-line 

Auto transmission upshifts too late 

Throttle valve 

Oil pressure insufficient 

Friction disk skids 

Governor valve 

Accumulator 

Repair or replace 

Repair or replace 

Adjust 

Repair 

Replace 

Replace 

Abnormal 

Normal 

Normal 

Normal 

Normal 

Normal 

Normal 

Normal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

 
 

 

 

186 

 

No. 137 Auto transmission unable to upshift   

Malfunction Causes 

Solution 

Auto transmission oil 

Check auto transmission oil is too little, and oil level shall 
be between 2-4 holes of dipstick; if too little, it will not 
generate oil pressure, making it unable to upshift;   

Throttle tie-line malfunction 

Check throttle tie-line, and step to the end, and throttle 
shall at maximum position. If not possible, adjust throttle 
tie-line; Check tie-line of throttle position of auto 
transmission; there shall be 2-8mm clearance between 
tie-line bottom and pedestal, and adjust it if not so; 

Governor valve malfunction 

Check speed control valve blocks or leaks or fails; if 
abnormal, repair or replace governor valve; 

Auto shifting valve malfunction 

Check auto shifting valve blocks or leaks; if abnormal, 
adjust or replace valve plate assembly;   

Accumulator malfunction 

Check accumulator blocks, or is worn, leaking; check 
accumulator spring conforms to requirement; if abnormal, 
adjust or replace seal or spring; 

Auto transmission 

unable to upshift 

Drive-gear control valve malfunction 

Check drive-gear clutch piston blocks or leaks; if 
abnormal, adjust or replace drive-gear clutch parts; 

 

Auto transmission unable to upshift 

Auto transmission oil liquid 

Throttle tie-line 

Governor valve 

Auto shifting valve 

Accumulator 

Drive-gear control valve 

Repaiar or replace 

Replace 

Repair 

Repair 

Adjust 

Check and fill 

Abnormal 

Normal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Normal 

Normal 

Normal 

Normal 

 
 

 

 

187 

 

No. 138 Auto transmission unable to force downshift   

Malfunction Causes 

Solution 

Throttle tie-line malfunction 

Check throttle tie-line, and step to the end, and throttle 
shall at maximum position. If not possible, adjust throttle 
tie-line; Check tie-line of throttle position of auto 
transmission; there shall be 2-8mm clearance between 
tie-line bottom and pedestal, and adjust it if not so; 

Control valve malfunction 

Check control valve plate blocks or leaks inside; if 
abnormal, repair or replace; 

Governing valve malfunction 

Governing valve severely worn, causing pressure relief, 
thus unable to downshift; replace governing valve 
assembly;  

Forced downshift switch malfunction 

Check forced downshift switch is ok; if abnormal, replace 
it, and if normal, check tie-line from downshift switch to 
control unit is normal, and if so, check control unit is ok, 
and if not so, replace it;   

Auto transmission 
unable to force 
downshift 

Forced-gear solenoid valve damaged 

Check solenoid valve switch is damaged; by referencing 
circuit drawing, check there is open circuit, short circuit; 
replace solenoid valve;   

 

Auto transmission unable to force 

downshift 

Throttle tie-line 

Control valve 

Forced downshift switch 

Forced-gear solenoid valve 

damaged 

Repaiar or replace 

Adjust 

Replace 

Replace 

Abnormal 

Normal 

Normal 

Normal 

Abnormal 

Abnormal 

Abnormal 

 
 

 

 

188 

 

No. 139 Engine shuts down after putting into gear   

Malfunction Causes 

Solution 

Idling speed too low or clutch too low; 
throttle blocks 

Clean idling motor or replace, and adjust clutch height, or 
replace throttle tie-line; 

Idling motor poorly operates   

Clean or replace idling motor;   

Check signal panel loosens; repair or replace parts and 
components;  

Rotating signal panel loosens or engine 
unusually operates   

Repair the engine, making it normal or replace damaged 
parts and components; 

Gear inside transmission worn, damaged or 
jammed, blocked 

Disassemble gear inside transmission; adjust or replace 
damaged parts and components; 

Clutch disk and flywheel locked or not fully 
separated  

Repair or replace parts and components; repair and separate 
fully or replace damaged parts and components; 

Engine shuts down 
after putting into 
gear 

Torque converter (with locking clutch) 
malfunction 

With power on, test locking clutch solenoid valve is normal; 
check resistance of control solenoid valve is up to standard; if 
not so, replace solenoid valve; if so, check tie line of solenoid 
valve and control unit is normal; if so, check control unit is ok; 
if not so, replace it; if solenoid valve and control unit tie-line, 
control unit are all normal, clean or replace torque converter; 

 

Engine shuts down after putting into gear 

Idling speed too low or clutch too low; throttle 

blocks 

Idling motor poorly operates 

Rotating signal panel loosens or engine 

unusually operates 

Gear inside transmission worn, damaged or 

jammed, blocked 

Torque converter 

Clean or replace 

Replace 

Repair 

Repair 

Repair 

Abnormal 

Normal 

Normal 

Normal 

Normal 

Abnormal 

Abnormal 

Abnormal 

Abnormal