In an Allison automatic transmission used in a school bus, what component multiplies engine torque during vehicle launch?
Automatic Transmission
Question · Easy
What allows torque multiplication to stop and the torque converter to act as a near 1:1 fluid coupling at cruising speed?
Question · Medium
Technician A says the torque converter lockup clutch eliminates converter slip to improve fuel economy and reduce fluid heat. Technician B says lockup is normally applied in the lowest gear during launch. Who is correct?
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A school bus Allison transmission exhibits a shudder felt only when the converter lockup clutch applies at light throttle. The MOST likely cause is:
Which transmission fluid specification is required for most current Allison automatics used in school buses?
When checking Allison transmission fluid level with the electronic oil level sensor and shift selector display, the fluid should be at:
A bus Allison transmission fluid is dark brown and smells burnt. This MOST directly indicates:
In a planetary gearset, holding the ring gear, driving the sun gear, and taking output from the carrier produces:
In a simple planetary gearset, reverse output is produced when the:
Direct drive (1:1) through a planetary gearset occurs when:
Modern Allison transmissions in school buses primarily produce gear changes using:
During a clutch-to-clutch upshift, a delayed release of the off-going clutch while the on-coming clutch applies will MOST likely cause:
Question · Hard
The TCM (Transmission Control Module) on a school bus Allison uses which input to help determine shift points?
A school bus Allison transmission goes into a limited-operation 'limp' mode and the wrench/CHECK TRANS lamp is on. The technician should FIRST:
Allison prognostics features such as oil life, filter life, and clutch (transmission health) monitors are intended to:
A stall test on a school bus automatic transmission is performed to evaluate:
During a stall test, recorded stall speed is well BELOW the manufacturer's specification. This MOST likely indicates:
During a stall test, stall speed is significantly ABOVE specification. The MOST likely cause is:
A hydraulic pressure test on an Allison transmission is used MAINLY to:
Low main line pressure at all operating ranges on a bus automatic is MOST likely caused by:
Technician A says an Allison output retarder uses fluid friction to slow the vehicle and creates heat that the cooling system must dissipate. Technician B says the retarder increases engine compression braking only. Who is correct?
A school bus equipped with an Allison output retarder overheats the transmission only during long downhill braking. The technician should FIRST inspect the:
The transmission fluid temperature on a school bus Allison reads 280°F (138°C) and rising during normal level-road driving. The technician should:
What is the function of the transmission cooler in a school bus drivetrain?
Milky pink transmission fluid found during service MOST likely indicates:
The transmission filter in an Allison automatic primarily:
After a clutch failure releases debris into an Allison transmission, the recommended practice during overhaul is to:
A shift solenoid in an Allison transmission electrohydraulic control is responsible for:
A school bus Allison transmission will not upshift out of first gear and a shift solenoid circuit DTC is stored. The BEST next diagnostic step is to:
The turbine (input) speed sensor on an Allison transmission provides the TCM with:
The output speed sensor signal on a school bus automatic transmission is used by the TCM MAINLY to:
A bus develops harsh, late upshifts after a battery was disconnected and reconnected. The MOST likely explanation is:
On an Allison automatic, the function of adaptive (clutch fill) learning is to:
A no-movement condition in both forward and reverse on a bus Allison, with normal engine RPM and a quiet transmission, MOST likely indicates:
A school bus automatic slips and flares only on the 2-3 upshift but shifts normally elsewhere. This MOST specifically indicates:
Why must the correct TES-approved fluid be used rather than a generic ATF in an Allison bus transmission?
Aerated (foamy) transmission fluid in a school bus Allison is MOST likely caused by:
The park pawl in an Allison automatic transmission used in a school bus:
A bus Allison transmission engages with a hard bump into Drive and Reverse from neutral. With normal fluid and codes present for low pressure, the technician should:
Technician A says converter slip is normal and desirable during launch for torque multiplication. Technician B says any slip when lockup should be applied at cruise indicates a problem. Who is correct?
The impeller (pump) of a torque converter is driven by and rotates with the:
Which converter component is splined to and drives the transmission input shaft?
A worn converter stator one-way clutch that slips during launch will MOST likely cause:
The valve body in an Allison automatic transmission primarily:
A sticking valve in the valve body of a school bus automatic transmission MOST commonly produces:
On a school bus Allison, the transmission oil pump is normally driven by the:
A school bus automatic transmission has good pressure cold but pressure drops and clutches slip as it warms. The MOST likely cause is:
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