190303F Flashcards
What are the five basic steps to trouble shooting a power shift or automatic transmission?
Step 1 gather information Step 2 talk to the operator Step 3 visual inspection Step 4 person operational tests Step 5 testing using specialized test equipment
What are three sources you can gather information from?
Service manuals
Service bulletins
Operator’s manuals
What is some typical information you can get from talking to the operator?
Maintenance procedures
Modifications to machine
Repairs to machine
Noises or erratic movements or other failures
What are some obvious visual signs on a machine?
Oil type, level and condition
Discoloured paint
Leaks
Damage
Transmission linkage in correct positions
Transmission mounts damaged or missing bolts
ETC
When performing operations tests, what is the first step that must be done to get an accurate assessment?
Machine’s oil must be at normal operating temperature. Usually between 65.5 degrees celsius and 82.20 degrees celsius.
How do you perform a torque converter stall test to help heat up oil?
Lock the service and park brake
Select highest possible speed range
Running the engine at wide open throttle
Record engine RPM on tachometer
How long should you a stall test for before cycling into neutral for cool down?
30 seconds to prevent over heating
What can cause a LOW stall speed?
The engine is not producing sufficient power
Torque converter stator is slipping
What can cause HIGH stall speed?
Engine is producing excessive power (over fuel)
Clutches are slipping inside transmission
Torque converter is cavitating (insufficient TC charge oil flow)
What should you do before performing basic pressure tests?
Stop the machine on level ground
Lower or mechanically block all work equipment (caulk wheels)
Apply the parking brake
What range should your testing pressure gauges be?
Two times expected pressure
What are the hydraulic circuits in a powershift or automatic transmission shift system?
Clutch application circuit
Torque converter charge circuit
Transmission lubrication circuit
An extremely low charge pump inlet pressure below 12 psia would mean?
A restriction on the pump inlet side
How is cavitation in the charge pump caused?
Too low of inlet pressure
Would the pressure be higher or lower than normal in the inlet to the charge pump if aeration is occurring?
higher
Where do you have to place a pressure gauge to read available clutch application pressure?
In series between the charge pump and clutch pressure regulator valve, it is in parallel with the shift selector valve.
How can you check for large internal leakage in the clutch application circuit?
Engine running at high and low idle, application pressure should not change with engine RPM
How do you adjust the clutch pressure regulator valve if possible?
With shims behind the spring
If the pressure reading is too low on the torque converter charging circuit what are the causes?
Insufficient charge pump flow
Excessive leakage in the clutch application circuit
Excessive leakage in the torque converter circuit
What can cause lube pressure to be too low?
Any excessive leakage in the three circuits or a charge pump not providing enough flow