T3 covers the truck drive train from the flywheel to the axle ends: 50 questions (40 scored) in 60 minutes, one of the two shortest T tests. The transmission is the largest of its four content areas, with the clutch close behind.
40 scoredquestions that count
60 mintesting time
20questions on the recert test
10practice questions here
What T3 covers
Checked Oct 23, 2026 against each source linked in the table. Content areas and scored questions from the spec table in the 2026 study guide, p. 17.
Question 1 of 10 · T3 Drive Train · 40 itemsNot answered
A driveshaft is being reassembled after a slip yoke is removed. Technician A says the inboard yokes should be 90 degrees apart. Technician B says the alignment marks on the slip yoke and tube shaft should be lined up. Who is right?
Explanation
Incorrect: The inboard yokes on one shaft are kept in phase (in line), not 90 degrees apart, so Technician A is wrong.
Correct: Lining up the slip yoke and tube marks puts the yokes back in phase, as they were built and balanced; setting the inboard yokes 90 degrees apart would cause vibration.
Incorrect: Only Technician B is right; yokes 90 degrees apart are out of phase and cause vibration.
Incorrect: Technician B is right: the alignment marks keep the slip yoke in phase with the tube yoke.
Question 2 of 10 · T3 Drive Train · 40 itemsNot answered
A drive axle is leaking gear oil at both the pinion seal and the wheel seals. Technician A says a plugged axle housing breather could be the cause. Technician B says the axle could be filled above the fill plug hole. Who is right?
Explanation
Incorrect: A plugged breather lets heat build pressure in the housing and push oil past the seals, but overfilling also forces oil out, so Technician B is right too.
Incorrect: Overfilling pushes oil out at the seals, but a plugged breather does the same by trapping pressure, so Technician A is right as well.
Correct: Leaks at both the pinion and wheel seals point to the whole housing: a plugged breather builds pressure in it, and overfilling floods the seals.
Incorrect: Both are common causes of oil pushed past several axle seals at once: a plugged breather and an overfilled housing.
Question 3 of 10 · T3 Drive Train · 40 itemsNot answered
A drive axle has a ring gear with 41 teeth and a drive pinion with 11 teeth. The axle ratio is:
Explanation
Correct: Axle ratio is ring gear teeth divided by pinion teeth: 41 ÷ 11 = 3.73, written 3.73:1.
Incorrect: 3.55:1 would need about 39 ring gear teeth on an 11-tooth pinion, not 41.
Incorrect: 3.91:1 would need 43 ring gear teeth on an 11-tooth pinion.
Incorrect: 0.27:1 comes from dividing the pinion by the ring gear, which turns the ratio upside down.
Question 4 of 10 · T3 Drive Train · 40 itemsNot answered
The lubricant level in a heavy-duty manual transmission is being checked with the truck parked level. The level is correct when it is:
Explanation
Incorrect: Heavy-duty manual transmissions do not use a fill plug dipstick; the hole itself is the full mark.
Incorrect: Lubricant you can only reach with a finger joint is low, which shortchanges the gears and bearings.
Correct: A manual transmission has no dipstick; with the truck level, lubricant even with the bottom of the fill plug hole is full.
Incorrect: Lubricant 1/2 in. below the opening is low; it should be even with the bottom of the hole.
Question 5 of 10 · T3 Drive Train · 40 itemsNot answered
A synchronized medium-duty 6-speed transmission grinds only when shifted into third gear. Technician A says a worn third-gear blocker ring could be the cause. Technician B says a clutch that does not fully release could be the cause. Who is right?
Explanation
Correct: A worn third-gear blocker ring cannot match speeds before the sleeve engages, so only third gear grinds; a dragging clutch would make every gear grind.
Incorrect: A clutch that does not fully release makes shifts grind into every gear, especially first and reverse from a stop, so it does not fit a grind in third only.
Incorrect: Only Technician A is right; the grind in one gear only rules out a dragging clutch.
Incorrect: Technician A is right: a worn blocker ring for third gear explains a grind in that gear only.
Question 6 of 10 · T3 Drive Train · 40 itemsNot answered
The backup lamps on a truck do not work. The bulbs are good, and there is battery voltage at the reverse light switch input but none at its output with reverse selected. Which of these could be the cause?
Explanation
Incorrect: An open in the wire beyond the switch would not take away the voltage measured at the switch output terminal.
Incorrect: An open ground at the lamps would still leave voltage at the switch output; it would only stop current flowing through the lamps.
Correct: With power going into the switch and none coming out in reverse, the switch is not closing, so it has failed or is not being actuated.
Incorrect: A blown fuse would leave no voltage at the switch input, but the input has battery voltage here.
Question 7 of 10 · T3 Drive Train · 40 itemsNot answered
When a gear-driven power take-off (PTO) is mounted to a transmission, the thickness of the mounting gaskets or spacers sets the:
Explanation
Incorrect: Shift fork clearance is internal to the PTO and is not set by the mounting gaskets.
Correct: Gaskets or spacers move the PTO toward or away from the transmission gear, which sets the backlash between the PTO and transmission gears; too little whines or binds, too much rattles.
Incorrect: PTO output shaft end play is set inside the PTO by its bearings and shims, not by the mounting gaskets.
Incorrect: The PTO speed ratio is fixed by its gears; gasket thickness cannot change it.
Question 8 of 10 · T3 Drive Train · 40 itemsNot answered
The shift lever on a truck jerks forward and backward when the driver accelerates and releases the throttle. Which of these could be the cause?
Explanation
Incorrect: Weak detent springs let the transmission jump out of gear; they do not make the lever rock with the throttle.
Incorrect: A worn release bearing makes noise when the clutch is pressed; it does not move the shift lever.
Correct: A broken transmission mount lets the powertrain rock with each change in torque, which moves the shift lever back and forth.
Incorrect: Loose shift tower screws give a sloppy lever, but the jerking that follows the throttle comes from the powertrain moving on a broken mount.
Question 9 of 10 · T3 Drive Train · 40 itemsNot answered
A new U-joint is being installed. Technician A says the bearing caps should be seated by striking them with a steel hammer. Technician B says the joint is properly lubricated if grease purges from three of the four seals. Who is right?
Explanation
Incorrect: Striking the caps with a steel hammer can brinell the needle bearings and crack the cap, so caps are pressed or tapped with a soft tool; Technician A is wrong.
Incorrect: Grease must purge from all four bearing seals; a seal that stays dry means that bearing is not getting grease, so Technician B is wrong.
Incorrect: Neither practice is right: hammering damages the bearings, and grease must purge from all four seals.
Correct: Caps are pressed in or seated with a soft tool, not a steel hammer, and a new joint is greased until fresh grease purges from all four seals.
Question 10 of 10 · T3 Drive Train · 40 itemsNot answered
Flywheel face runout is measured at four points with crankshaft end play held out. The readings are +0.002, +0.001, -0.002 and 0.000 in. The manufacturer's limit is 0.005 in. The flywheel is:
Explanation
Correct: Total indicated runout is the highest reading minus the lowest: +0.002 − (−0.002) = 0.004 in., under the 0.005 in. limit.
Incorrect: 0.006 in. overstates the swing; from −0.002 to +0.002 is 0.004 in.
Incorrect: 0.002 in. is just the largest reading; runout counts the full swing from the lowest reading to the highest.
Incorrect: 0.005 in. comes from adding the numbers without regard to sign, which is not how runout is read.
Answer every question to see your score
Area by area
Clutch
11 scored questions: noise, slip, chatter and drag; linkage, hydraulic and air-assist release; single- and two-plate clutches; self-adjusting clutches; the clutch brake; pilot bearing and flywheel checks. The clutch brake stops the countershaft so you can shift into first or reverse with the truck standing still. It is not for upshifts.
Transmission
13 scored questions: wear and failure analysis, jumping out of gear, air shift controls for range and splitter, electronic and automated controls diagnosed with a scan tool, lubrication and cooling.
Driveshaft & universal joint
7 scored questions: vibration diagnosis, U-joints, slip yokes, center bearings, phasing and working angles. Yokes on a two-piece shaft are in phase when they line up; working angles should be small and nearly equal at both ends of a shaft, but not zero, or the needle bearings stop rotating and brinell.
Drive axle
9 scored questions: gear noise under drive or coast, ring and pinion contact pattern, backlash and runout, inter-axle differentials and their locks, axle shafts and wheel-end seals.
Never lock the inter-axle differential on a spinning wheel
Engaging the inter-axle lock while a wheel is already spinning shock-loads the power divider. Stop, engage the lock, then pull away.