F6 Allison Automatic Transmissions — practice test

High-yield F6 topics

The material that shows up year after year. If you're short on time, start here.

• Clutch chart for the 3000/4000: exactly two clutches apply per range. R = C3+C5, 1st = C1+C5, 2nd = C1+C4, 3rd = C1+C3, 4th = C1+C2 (direct 1.00:1), 5th = C2+C3, 6th = C2+C4. They test it as a diagnostic: slips in first AND reverse but is fine elsewhere means the shared clutch (C5) is the fault, not low main pressure. Memorize the chart and practice finding the common element.
• Torque converter failure modes as look-alikes. Stator one-way clutch SEIZED = strong launch, then overheating and no top speed (stator will not freewheel at coupling speed). Stator one-way clutch SLIPPING/freewheeling = sluggish off idle with no torque multiplication, but normal top speed and no heat. Stall speed high = slipping clutches or converter; stall low with no other symptom = the engine is down on power, not the converter.
• Electronic oil level check conditions, all of them: engine at idle, transmission in Neutral, vehicle stopped on level ground with the parking brake set, output shaft not rotating, and sump temperature inside the valid window (roughly 140-220 F). Display reads oL, then OK / LO / HI with a quart count - oL LO 02 means two quarts low. Miss one condition and you get an invalid-check code, not a level.
• Split-shaft pump shift sequence and NFPA interlocks. Complete stop, selector to Neutral, parking brake set, wheels chocked, make the pump shift (air pressure must be up), THEN select Drive and confirm the speedometer indicates road speed - that is what proves the driveline is turning the pump. Green indicators required in the cab (pump engaged, OK to pump) and at the pump panel. The fire/emergency calibration commands converter lockup in pump mode to keep converter slip from cooking the fluid.
• Integral output retarder: hydrodynamic, fluid filled, retarding torque roughly proportional to the SQUARE of output shaft speed. It is inhibited in Neutral, inhibited below a minimum output speed, and released when ABS activates. Its heat goes into the transmission fluid, out through the cooler, and into the engine coolant - which is why coolant temp climbs on a long retarder descent and why retarder units need more cooling capacity. NFPA requires an auxiliary brake at 36,000 lb GVWR and above.
• Fluid specs and prognostics. TES 389 is conventional; TES 295 / 468 / 668 are the full-synthetic specs (TranSynd), with TES 668 superseding 295. Prognostics (Oil Life, Filter Life, Transmission Health monitors) is only validated on TES 295/668 fills - and the monitors must be RESET after a fluid and filter service. 3000/4000 units carry two filters. Pink and milky fluid = coolant intrusion through the cooler, not normal new-fluid appearance.

Where techs lose points on F6

Good technicians miss these — not from lack of skill, but because the question is built to catch them.

• "Put it in Park." Allison automatics on fire apparatus have no mechanical park pawl. Any answer that secures the apparatus for stationary pumping by selecting Park is wrong - the correct answer is parking brake set plus wheel chocks, and chocks are not optional.
• Assuming the retarder can hold the truck on a grade. It cannot. Retarding effort falls off with the square of speed, so it fades to nothing near zero output speed. Same trap in reverse: a complaint of "strong retarder at highway speed, almost none as it slows" is normal hydrodynamic behavior, not a defect - and rising coolant temp during retarder use is the cooling path working, not a bad retarder.
• Only worrying about low fluid. Overfill aerates the fluid, and foamy fluid drops main pressure, causing erratic shifts, slipping, and overheating - the same symptom set as underfill. When a question gives you foamy fluid plus overheating, do not reflex to "low level." Related: a valid level check requires a hot sump, so "check it cold right after startup" is always the wrong technician.
• Chasing a fault when the speedometer reads road speed while the truck is parked in pump mode. That is normal - the output shaft is turning the pump. And after a TCM swap, harsh shifts plus a high-reading speedometer is a calibration problem (wrong tire rev/mile or axle ratio), not a bad sensor or a failing clutch.

A study plan that works for F6

Roughly two weeks of real preparation, in the order that actually builds on itself.

1. Days 1-3: Fundamentals you cannot fake. Draw the 3000/4000 clutch chart from memory every morning until you can do it in under a minute, then work backward from symptoms (which clutch do these two failing ranges share?). Same block: converter elements - impeller bolted to the cover, turbine, stator with its one-way clutch - plus vortex vs rotary flow and the four stall-test outcomes.
2. Days 4-6: Electronics. TCM inputs (input/turbine/output speed sensors as variable-reluctance pickups, TFT thermistor, throttle over J1939) and outputs (pressure-control variable-bleed solenoids, lockup, retarder modulation). Learn how the TCM verifies commanded range by comparing turbine to output speed, what DNS does and why, WTEC III two-digit main/sub codes vs Gen 4-5 SAE P-codes, and what Allison DOC is used for.
3. Days 7-9: The fire-specific half, which is where the test is won. Split-shaft pump-shift sequence and every interlock condition, OK-to-Pump indicator logic, hot-shift vs constant-mesh PTO, pump-and-roll, retarder inhibits and cooling, and the full TES fluid/prognostics picture including monitor resets. If you only have time for one area, make it this one.
4. Days 10-12: Drill in exam format only. Nothing but Technician A/B and EXCEPT questions until the wording stops fooling you, and log every miss by task area. Two days out, stop learning new material and re-drill your logged misses plus the clutch chart. Walk in able to recite the oil-level-check conditions and the pump-shift sequence cold.

Sample F6 questions

Straight from the bank — answers highlighted, with the explanation underneath.