Five free practice questions on drive axles and differentials: content area E of the ASE A3 Manual Drive Train & Axles test, 7 of its 40 scored questions (17.5%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.
01The questions
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Before removing a rear axle's companion flange to replace the pinion seal, a technician scribes marks across the end of the pinion stem and the flange. What are the marks for?
- Keeping the flange and drive shaft in balance
- Keeping the pinion depth setting unchanged
- Keeping the drive shaft's universal joints in phase
- Keeping the ring and pinion contact pattern the same
Show the answer
A. Correct. The flange, pinion and drive shaft run as a balanced assembly, and refitting the flange in its original spline position keeps that balance so a vibration is not added. The marks are lined up again when the flange goes back on.
Why not the others
B. Pinion depth is set by a shim at the pinion head or bearing cup and is not affected by where the flange sits on the splines. The marks keep the flange in its original spline position so driveline balance is kept.
C. Phasing is the alignment of the yokes at the two ends of the drive shaft, fixed when the shaft is built or at a slip spline within it, and the flange's spline position on the pinion does not change it. The marks keep the flange in its original spline position so the assembly stays in balance.
D. The contact pattern depends on pinion depth and backlash, which the flange's spline position does not change. The marks let the flange go back in its original position to keep the assembly in balance.
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During a ring and pinion installation on an axle with a collapsible spacer, how is drive pinion bearing preload measured?
- As the torque to keep the pinion turning, case out
- As the torque to start the pinion turning, case out
- As the torque to keep the pinion turning, case in
- As pinion end play read with a dial indicator
Show the answer
A. Correct. Preload is read with an inch-pound torque wrench as the torque needed to keep the pinion turning steadily, after rotating it to seat the bearings. The differential case is left out so ring gear mesh and side bearing drag do not add to the reading.
Why not the others
B. The torque to break the pinion loose is higher and less consistent than the turning torque, so it overstates preload. The specification is the torque to keep the pinion turning steadily, read with the case out.
C. With the case installed, ring gear mesh and side bearing preload add drag, so the reading is total preload, not pinion bearing preload. Pinion preload is read as turning torque before the case goes in.
D. Preloaded bearings have no end play to read; end play is the opposite condition. Preload is measured as the torque needed to keep the pinion turning, with the case out.
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A new ring and pinion are set up with backlash in specification. Marking compound shows the drive-side pattern centered between heel and toe but running along the top (face) of the ring gear teeth, and the coast side the same. On this axle the pinion depth shim sits under the pinion head. What should the technician do?
- Increase backlash within specification
- Fit a thinner pinion depth shim
- Reduce backlash within specification
- Fit a thicker pinion depth shim
Show the answer
D. Correct. A pattern high on the face of the teeth means the pinion sits too far from the ring gear's centerline. A thicker shim under the pinion head moves it in, which moves the pattern down toward the flank; check backlash and the pattern again after the change.
Why not the others
A. More backlash mainly moves the drive-side pattern toward the heel, and the pattern here is already centered heel to toe. A face pattern on both sides is corrected with pinion depth: a thicker shim on this axle.
B. A thinner shim moves the pinion farther from the ring gear's centerline, which pushes the pattern even higher on the face. A face pattern needs more pinion depth: a thicker shim here.
C. Changing backlash mainly moves the pattern toward the toe or heel, and this pattern is already centered heel to toe. Its position high on the face shows the pinion depth is wrong, so a thicker shim is needed.
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A clutch-type limited-slip rear differential is being rebuilt, and its old friction and steel plates are laid out for inspection. Technician A says a friction plate whose oil grooves have worn away is replaced. Technician B says the plates must go back in the stacking order the manufacturer specifies. Who is right?
- A only
- B only
- Both A and B
- Neither A nor B
Show the answer
C. Correct. Both are right. Technician A: the grooves carry lube across a friction plate's face, and once they are worn away the lining is thin and the plate can neither hold nor cool properly, so it is replaced. Technician B: the order of friction and steel plates sets how many surfaces share the clamping force, so the manufacturer's stacking order is kept to get the specified locking.
Why not the others
A. Technician A is right, but so is Technician B. A friction plate whose oil grooves are gone has worn away much of its lining, and the plates go back in the manufacturer's stacking order because the order sets how many friction surfaces share the load and so how strongly the unit locks.
B. Technician B is right, but so is Technician A. The stacking order is the manufacturer's because it sets how strongly the unit locks, and a friction plate with its oil grooves worn away has lost much of its lining and is replaced.
D. Both technicians are right. Technician A is right that a friction plate with its oil grooves worn away is replaced, and Technician B is right that the plates go back in the stacking order the manufacturer specifies.
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On a heavy-duty pickup with a full-floating rear axle, why can an axle shaft be pulled out without removing the wheel?
- The shaft's bearing slides out with the shaft
- The shaft's C-lock is released from outside
- The hub rides on bearings on the axle housing
- The shaft's outer end carries the vehicle's weight
Show the answer
C. Correct. On a full-floating axle the wheel hub turns on its own bearings mounted on the end of the axle housing, and the shaft only bolts to the hub to drive it. Removing the flange bolts lets the shaft slide out while the hub and wheel stay in place on the housing.
Why not the others
A. A bearing pressed on the shaft that comes out with it describes a semi-floating axle, where the shaft carries the wheel. On a full-floating axle the hub's bearings stay on the housing and the shaft slides out alone.
B. C-locks hold semi-floating shafts and are removed from inside the differential, not from the wheel end. A full-floating shaft comes out because the hub turns on bearings on the housing, independent of the shaft.
D. That describes a semi-floating axle, where the shaft supports the wheel. On a full-floating axle the housing and hub bearings carry the weight, so the shaft can be pulled without removing the wheel.
02Answer key
| Question | Answer |
|---|---|
| Q1 | A |
| Q2 | A |
| Q3 | D |
| Q4 | C |
| Q5 | C |
03What area E covers
This content area covers the drive axle from the pinion flange out to the wheel studs. Questions deal with axle noise and leaks, pinion seals and flange runout, ring and pinion setup by pinion depth, bearing preload, backlash and tooth contact patterns, differential and limited-slip parts, electric lockers, the right gear oil, and semi-floating and full-floating axle shafts, bearings and seals.
The ASE test specification calls this content area “Drive Axle Diagnosis and Repair”. It carries 7 of the 40 scored questions, 17.5% of the test.
- Diagnose axle noise, vibration and leaks
- Replace pinion seals; check flange and ring gear runout
- Set pinion depth and pinion bearing preload
- Adjust side bearing preload and backlash
- Read ring and pinion contact patterns
- Service differentials, limited-slip units and lockers
- Replace axle shafts, bearings, seals and studs
- Check axle end play, the housing and its vent
04What the questions turn on
Reading the contact pattern
Changing pinion depth moves the pattern toward the face or flank of the teeth, while adding backlash moves the drive-side pattern toward the heel. A pattern high on the face means the pinion sits too far from the ring gear's centerline.
Preload is turning torque
Pinion bearing preload is the torque needed to keep the pinion turning, read with an inch-pound torque wrench with the differential case out. With a solid spacer and shims, a thinner shim pack draws the bearing cones closer and raises preload.
Count how often it knocks
Driving straight, the ring gear turns once per wheel revolution, while the pinion and drive shaft turn the axle ratio times as often. A single knock once per wheel turn points to one damaged ring gear tooth rather than the pinion or its bearings.
Limited-slip breakaway torque
Preload springs keep a clutch-type limited-slip unit's packs lightly applied at all times. A turning-torque check with one wheel raised that reads well under the minimum means the packs are not holding, from worn plates or weak preload springs.
05The other content areas
The A3 test has six content areas. Each has its own page of free questions:
The ASE A3 Manual Drive Train & Axles practice test page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.
ToolboxPrep is an independent study site. It is not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original practice questions written to the published ASE test specifications; they are not actual test questions.