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
What two circuits that act as inputs, that are always supplied by the clutch application circuit?
Clue: not the torque converter or transmission lube circuit.
Governor circuit
Modulator circuit
Testing with a flowmeter is more accurate than pressure testing. T/F
True
Flowmeters can tell you what about leakage in the circuits?
The amount of oil leakage
How are shift points adjusted in an automatic transmission?
by adjusting the spring tension on the shift signal valves
What is needed to adjust shift points?
Specialized tools and test stands
What provides self diagnostics?
ECU
How does the ECU detect faults?
Reading inputs and comparing them to the range given by its internal programming
What is a FMI?
FAULT MODE IDENTIFIER
What is CID?
COMPONENT INDENTIFIER
How does a Check Transmission Light provide codes?
Flashing Light in diagnostic mode
What are two ways to access fault codes?
Data line scanners
Computer
Digital display in machine
What are four electrical faults?
Open
Short - to ground
Short - to circuit
High Resistance
How to protect the ECU from high voltage or surges?
Unplug the ECU
DO NOT use fast charges to start the engine
Remove batteries to use fast charges
NEVER disconnect the battery while engine is running
Do NOT open electrical connections when system is operational or running
What should be check before connecting any wiring components?
Make sure connections are clean and fit snug
What should the ECU be protected from other than high voltage and surgers?
High heat
What should always be done before removing transmissions?
Heed all safety information and warnings.
What should be done instead of allowing a machine to be solely supported by a hoist or jack?
The machine should be securely blocked or placed on appropriate stands.
Before removing any part of the transmission what should be done to the system for safety?
Drain all air and hydraulic pressures, be aware of accumulators. Follow manufactures recommendations to completely relieve systems.
Why is cleanliness important during removal, repairs, replacement and installation of transmission parts?
Due to tight clearances and small orifices any debris or dirt can plug, damage or effect performance of the transmission parts and circuits.
What is an important step to remember before re assembling a transmission?
Pre-lube all necessary parts, some parts may need to be submerged for a length of time to absorb lubrication.
What would happen if you were to nick or scratch a valve surface?
The valve will stick
What are some conditions that can be checked on a transmission bearing?
rough rotation chipped races defective bore mating surface scoring pitting wear
What should clutch friction discs be inspected for?
burrs embedded metal particles severely pitted friction materials cracks and distortion flaking friction material damaged spline teeth
The steel reaction discs should be visually inspected for?
burrs embedded metal scoring signs of overheating cracks damaged tangs
How can you measure a friction disc for wear?
Outside micrometer in atleast 3 places
Check against manufacture specs
How can you measure warpage on a friction disc?
Place disc on a flat surface and use feeler gauges to determine amount of warpage.
Check against manufacture specs
What part can be changed to adjust clutch clearance?
Clutch Piston
If you improperly install a valve body what could happen?
If the valve body is not installed by using correct procedure and torque it can warp. Causing valves to stick or not move.
When performing a stall test you must be careful not to?
overheat the transmission oil
Disc warpage and cone are measured using?
feeler gauges
