Automatic Transmission/Transaxle Flashcards

You're inspecting the color of the fluid in an automatic transmission/transaxle. Which of the following will cause the fluid to be varnished with a light to dark brown color?

Answer: Oxidation from overfilling

Correct answer: Oxidation from overfilling Oxidation from under or overfilling will cause the fluid to be varnished with a light to dark brown color.

An automatic transmission does not hold in PARK. Technician X says that misadjusted shift linkage could be the cause. Technician Y says that a roller clutch installed backwards could be the cause. Who is right?

Answer: X only

The PARK mechanism in an automatic transmission relies on a parking pawl engaging a parking gear. If the shift linkage is misadjusted, the pawl may not fully engage, preventing the transmission from holding in PARK. A roller clutch, on the other hand, is an internal component for one-way rotation and is not directly involved in the parking function; installing it backwards would affect drive engagement, not the parking mechanism.

An automatic transaxle loses pressure as it shifts from first to second gear. Technician X says this could be caused by the clutch piston seal. Technician Y says this could be caused by a stuck servo. Who is correct?

Answer: X only

A clutch piston seal is vital for maintaining hydraulic pressure within a clutch pack, which is necessary for engaging and holding a gear. If this seal is faulty, pressure can leak, leading to a loss of engagement during a shift, such as from first to second gear. A stuck servo would typically cause a harsh shift or prevent a gear from engaging, rather than a pressure loss during the shift itself.

Shifting from Neutral to Drive with an electronically controlled 4-speed automatic transaxle produces a "shock." Which of these requires an off-vehicle repair?

Answer: Forward clutch

A 'shock' when shifting from Neutral to Drive often indicates an issue with the initial engagement of the forward clutch, which transmits power in drive ranges. Problems with the forward clutch, such as worn friction material or a faulty piston, require the transmission to be disassembled and removed from the vehicle for repair. Other options like the control valve or sensors can often be addressed with the transmission in place.

The torque converter does which of the following when an engine is removed from a vehicle with an automatic transmission?

Answer: Stays with transmission

The torque converter is designed to mate directly with the input shaft of the automatic transmission and is bolted to the engine's flex plate. When the engine is removed, the torque converter should be carefully unbolted from the flex plate and remain seated in the transmission case. This prevents damage to the transmission's input shaft and pump, which are critical components.

When it's cold, the transmission slips. Which of these possibly be the cause of the problem?

Answer: Low line pressure

When an automatic transmission slips, it indicates insufficient hydraulic pressure to fully engage the clutches or bands. Low line pressure, especially when cold, means the fluid is thicker and the pump or pressure regulator might not be generating enough force to properly apply the friction elements. This can lead to delayed engagement or slipping until the fluid warms up and its viscosity decreases.

Hard shifting is the problem with an automatic transmission in a light truck. Technician X says a problem with the accumulator will result in this condition. Technician Y says a sticking restricting orifice/check ball will result in this condition. Who is correct?

Answer: Both X and Y

Accumulators are designed to cushion shifts by absorbing hydraulic pressure spikes, ensuring smooth gear changes; a problem with an accumulator would lead to harsh shifts. Similarly, a sticking restricting orifice or check ball in the valve body can disrupt the precise flow and timing of hydraulic fluid, causing abrupt pressure changes and resulting in hard shifts. Therefore, both conditions can cause hard shifting.

You intend to diagnose a RWD, electronically controlled 5-speed automatic transmission that makes an unusual noise while in drive using your diagnostic symptom chart. Technician X believes that the oil pump assembly might the cause and requires an OFF-vehicle procedure. Technician Y states it is the control valve and that requires an OFF-vehicle procedure. Who is correct?

Answer: Technician X

An unusual noise, especially one present in drive, can often be attributed to mechanical components like the oil pump assembly. The oil pump is a critical rotating component that can generate noise if it's worn or damaged, and its repair or replacement typically requires the transmission to be removed from the vehicle. A control valve issue is less likely to produce a distinct 'unusual noise' and might not always require off-vehicle repair.

Which of the following will an automatic transmission pressure test reveal?

Answer: Dirty transmission filter

A line pressure test measures the hydraulic pressure within the transmission, which is vital for proper operation. A dirty or clogged transmission filter restricts the flow of fluid to the oil pump, leading to a significant drop in line pressure. This reduced pressure would be evident during a pressure test, indicating a potential issue with fluid supply or the filter itself.

During normal acceleration, the automatic transaxle upshifts harshly. It's possible that the cause is a failure:

Answer: throttle position sensor

The throttle position sensor (TPS) provides crucial input to the transmission control module (TCM) regarding engine load and driver demand. If the TPS fails or provides an incorrect signal, the TCM might command higher line pressure or faster, firmer shifts, resulting in harsh upshifts during normal acceleration. The other sensors primarily affect engine performance, not direct transmission shift feel.

All of the following components can prevent the torque converter clutch from applying, except :

Answer: the intake air temperature sensor

The torque converter clutch (TCC) application is controlled by the transmission control module (TCM) based on various inputs to optimize fuel economy. The throttle position sensor (engine load), engine coolant temperature sensor (to prevent TCC lockup when cold), and brake on/off switch (to disengage TCC when braking) are all critical inputs that can prevent TCC application. The intake air temperature sensor, while important for engine fuel management, typically does not directly inhibit TCC lockup.

Technician X believes you should listen to the customer’s concerns and find them as described in the online service information. Technician Y thinks that you should pick the symptom that matches the online information the closest based on the customer’s concern. Who is correct?

Answer: Technician Y

Customers often describe symptoms in their own words, which may not perfectly align with technical diagnostic terminology. Technician Y's approach of matching the customer's concern to the closest symptom described in the service information is a practical and effective diagnostic strategy. This allows the technician to translate the customer's subjective description into a standardized diagnostic path, even if the exact phrasing isn't identical.

All of the tests listed below are used to make a preliminary diagnostic on an electronically controlled automatic transmission/transaxle, except:

Answer: Flex plate check

Stall tests, line pressure tests, and fluid checks are common preliminary diagnostic procedures for automatic transmissions, evaluating torque converter, hydraulic system, and fluid health respectively. A flex plate check, while important for noise or vibration concerns, is typically a more involved inspection and not a standard preliminary diagnostic test for general transmission issues. It usually requires more disassembly or specific conditions to check.

The best technique to pinpoint an oil pressure leak with the transmission pan removed is to:

Answer: perform an air pressure test

With the transmission pan removed, an air pressure test is the most effective method to pinpoint internal hydraulic leaks. By applying regulated air pressure to specific passages or servo apply circuits, a technician can listen for air leaks or observe components moving, directly identifying where pressure is escaping. This allows for precise diagnosis of issues like faulty seals, gaskets, or cracked components that might be causing a pressure drop.

About bushing inspection and measurement, all of the following are correct except:

Answer: normal bushing clearance is 0.015 to 0.025 inch (0.381 to 0.635 mm).

While shaft-to-bushing clearance is critical and can be measured with precision tools, the specified range of 0.015 to 0.025 inches is excessively large for normal bushing clearance in an automatic transmission. Typical clearances are much tighter, usually in the range of a few thousandths of an inch (e.g., 0.001-0.005 inches) to ensure proper support and lubrication without excessive play. The other statements describe valid inspection and measurement techniques or indicators of wear.

Technician X believes that driveline, suspension and engine problems might look like they were caused by the transmission or transaxle. Technician Y says that you must start with a simple inspection to first ensure there’s nothing overlooked requiring a diagnostic scan tool. Who is correct?

Answer: Both X and Y

Technician X is correct because many vehicle symptoms, such as vibrations, noises, or performance issues, can originate from components outside the transmission but mimic transmission problems. Technician Y is also correct, as a thorough preliminary inspection (checking fluid level/condition, linkages, mounts, etc.) is a fundamental first step in diagnostics. This helps rule out simple issues before resorting to more complex tools like a scan tool, saving time and preventing misdiagnosis.

Technician X says low line pressure on an electronically controlled line pressure can cause the transmission to slip and operate sluggishly. Technician Y says line pressure varies with engine speed. Who is right?

Answer: X only

Technician X is correct because low line pressure directly impacts the ability of the transmission to apply clutches and bands with sufficient force, leading to slipping and sluggish operation. Technician Y is incorrect; while engine speed influences the output of the transmission pump, line pressure is primarily regulated by the pressure regulator valve, which maintains a relatively stable base pressure and then varies it based on load and gear selection, not simply engine speed alone.

Too much automatic transmission shaft end play could be caused by any of the following EXCEPT a worn:

Answer: clutch

Shaft end play is determined by the cumulative clearances between various thrust washers, bearings, and components along the length of the shaft, as well as wear in the transmission case or planetary carrier. A worn transmission case, planetary carrier, or selective washer can all directly increase end play. A worn clutch, however, primarily affects the engagement and holding capacity of a gear, not the axial end play of the main shafts.

All transmission pressures are normal at idle speed, but low at wide open throttle. Technician X says the Throttle Valve (TV) cable may need adjusting. Technician Y says the vacuum modulator may be damaged. Who is right?

Answer: Both X and Y

Both the Throttle Valve (TV) cable and vacuum modulator are mechanisms that signal engine load to the transmission, influencing line pressure. If the TV cable is misadjusted (e.g., too loose), it might not correctly signal increased throttle, leading to low line pressure at Wide Open Throttle (WOT). Similarly, a damaged vacuum modulator could fail to increase line pressure as engine load increases, resulting in low pressure at WOT. Therefore, both technicians are correct.

During the stall test, the RPM is lower than specified. Technician X claims that the turbine in the torque converter could be damaged. Technician Y thinks that some of the transmission clutches are slipping. Who is correct?

Answer: Neither technician

During a stall test, if the RPM is lower than specified, it indicates that the engine is struggling to overcome the load, meaning either the engine itself is weak or the torque converter is too tight (not slipping enough) or the transmission is not slipping. A damaged turbine or slipping clutches would cause the engine RPM to be higher than specified, as the engine would be able to rev more freely due to reduced load or power transfer.