ASE A2 Friction and Reaction Units — Questions and Answers
Question 1: A technician measures clutch pack clearance with a feeler gauge between the pressure plate and the snap ring and finds it greater than specification. Which correction is appropriate?
- Install a thinner selective snap ring
- Remove one steel plate and leave the friction plates
- Install a thicker selective snap ring or pressure plate (Correct answer)
- Use a weaker piston return spring
Correct answer: Install a thicker selective snap ring or pressure plate
A thicker snap ring or pressure plate takes up space in the stack and reduces clearance. A thinner one would increase it.
Clutch pack clearance is the gap left when the plates are stacked against the snap ring with the piston released. It is checked with a feeler gauge, or by measuring piston travel. Too much clearance gives slow, soft engagement and slippage. Too little causes drag and burned plates. Most units use a selective snap ring or pressure plate to set the clearance, and a thicker one reduces it. Always recheck after changing the part.
Question 2: When air testing an assembled clutch drum by directing compressed air into its apply passage, which result points to a failed piston seal?
- Air escapes with a hiss and the piston moves weakly or not at all (Correct answer)
- The piston moves with a soft thud and returns when the air is removed
- The piston moves and stays applied until the air is released
- The plates can be heard moving freely in the drum
Correct answer: Air escapes with a hiss and the piston moves weakly or not at all
If the piston seals leak, air escapes and the piston cannot build enough force to move. A good clutch applies with a dull thud and releases when air is removed.
Air testing checks the apply piston, its seals and the fluid passages. Use regulated, low-pressure shop air at the correct passage. A good clutch applies with a dull thud and releases cleanly. Audible leakage and little or no piston movement mean a damaged or missing seal, or a cracked piston or drum. A piston that sticks applied may point to a restriction or a stuck check ball.
Question 3: A technician disassembling a clutch pack finds the steel plates blued and the friction plates dark, glazed and flaking. What is the most likely cause?
- Using ATF of the wrong color
- Excessive piston return spring tension
- Over-torquing the clutch drum retaining nut
- Prolonged slippage that generated excessive heat (Correct answer)
Correct answer: Prolonged slippage that generated excessive heat
Blued steel plates and burned friction material result from heat produced by a slipping clutch.
Heat from slippage breaks down the friction lining and discolors the steel plates, which turn blue or show hot spots. The cause can be low clutch apply pressure, a leaking seal, too much clearance or a burned-out fluid condition. Replacing the plates without finding the cause leads to repeat failure. Check the piston seals, the oil passages and the hydraulic circuit.
Question 4: Why must new clutch friction plates be soaked in the specified ATF before assembly?
- To harden the friction lining so it lasts longer
- To saturate the lining so it does not scuff or burn on its first engagements (Correct answer)
- To shrink the plates to the correct thickness
- To remove the factory friction coating
Correct answer: To saturate the lining so it does not scuff or burn on its first engagements
Soaking saturates the lining with fluid so it is lubricated and cooled from the first apply. Dry plates can scuff or burn before fluid reaches them.
The lining on a friction plate is porous and absorbs ATF. If it is installed dry, the first engagements can overheat the lining or scuff it. Soak the plates for the time the manufacturer specifies, usually at least 15 to 30 minutes, in the specified fluid. Soaking does not change plate thickness or hardness. Measure clutch clearance after assembly.
Question 5: A technician checks an installed one-way roller clutch by turning the inner race by hand. Which behavior is correct for a good unit?
- It locks in both directions
- It rotates freely in both directions
- It locks in one direction and freewheels in the other (Correct answer)
- It drags equally in both directions
Correct answer: It locks in one direction and freewheels in the other
A one-way clutch must hold in its driving direction and overrun freely in the opposite direction.
One-way (roller or sprag) clutches hold torque in one direction and overrun in the other. Inspect the rollers or sprags, cage and races for wear, scoring and flat spots. If the unit locks both ways or slips both ways it must be replaced. An assembly installed backward gives the opposite of the designed behavior, so check the direction before final assembly.
Question 6: During air testing of a band servo, air is applied to the apply passage. Which result indicates a servo in good condition?
- The piston moves the apply pin smoothly and returns when the air is released (Correct answer)
- The pin moves only when the air is first applied and then stops
- Air escapes audibly from around the piston and cover
- The pin moves with a harsh bind and does not return
Correct answer: The piston moves the apply pin smoothly and returns when the air is released
A good servo moves smoothly with no audible leakage and returns under spring force when air is removed.
The servo piston applies the band through the apply pin. Air testing shows whether the piston seals and bore are sealed and the return spring works. Audible leakage means worn or damaged seal rings or a scored bore. A sticking or binding pin points to burrs, bent parts or debris. Also check the pin length, because it affects band adjustment.
Question 7: After installing a band with an external adjusting screw, what is the correct adjustment procedure?
- Tighten the screw as far as it will go and leave it
- Torque the screw to specification, then back it off the exact number of turns specified and tighten the lock nut (Correct answer)
- Back the screw out fully and tighten the lock nut
- Tighten the lock nut first and then set the screw by feel
Correct answer: Torque the screw to specification, then back it off the exact number of turns specified and tighten the lock nut
Bands are adjusted by torquing the adjusting screw to specification and then backing it off the specified number of turns before locking it.
The band must have the correct running clearance from the drum. If the adjustment is too tight, the band drags on the drum and overheats. If it is too loose, the band slips during application and burns. Use the service manual specification for torque and back-off turns. Hold the screw while tightening the lock nut so the setting does not change.
Question 8: During inspection of a clutch drum, a technician finds that the check ball in the piston area is stuck in its seat. What problem can this cause?
- Harsh upshifts only
- Low line pressure in all gears
- A leaking torque converter
- The clutch may drag because residual fluid is not released from the apply chamber (Correct answer)
Correct answer: The clutch may drag because residual fluid is not released from the apply chamber
The check ball opens to dump trapped fluid when apply pressure drops. If it sticks, centrifugal pressure may keep the clutch partly applied.
A rotating clutch drum spins fluid outward, which creates centrifugal pressure in the apply chamber. The check ball is thrown off its seat when pressure drops, releasing this fluid so the piston returns fully. A stuck or missing ball can leave the clutch partly applied, causing drag, burned plates or a bind-up. Test the ball for free movement and for a seal when seated.
Question 9: Which condition most likely results from too much clutch pack clearance?
- Clutch drag and plate burning in neutral
- Delayed or slipping engagement because the piston must travel farther before clamping the plates (Correct answer)
- Excessively fast, harsh release
- Increased line pressure
Correct answer: Delayed or slipping engagement because the piston must travel farther before clamping the plates
Excess clearance means the piston has more travel before clamping, so the clutch engages late and may slip.
With too much clearance, the piston travels farther before the plates are clamped. This gives a delay or flare on application and can let the clutch slip while pressure builds, which burns the plates. Too little clearance causes the opposite: drag when the clutch should be released. This is why clearance is measured on assembly rather than assumed.
Question 10: A technician checks steel clutch plates and finds one that is dished and warped. What should be done?
- Replace the plate, because warping causes uneven clamping and hot spots (Correct answer)
- Reinstall it facing the other way
- Flatten it in a vise
- Install it as the last plate in the stack
Correct answer: Replace the plate, because warping causes uneven clamping and hot spots
Warped steel plates do not clamp evenly, which causes hot spots, drag or slip. They should be replaced.
Steel plates are checked for flatness, discoloration, scoring and worn drive lugs. A plate that is dished or warped will contact the friction plate unevenly, concentrate heat and cause drag or slippage. Flipping or straightening does not restore it reliably. Replace damaged steel plates, and check the clutch clearance after assembly.
Question 11: When installing a lip-type seal on a clutch apply piston, how should the seal lip face?
- Away from the pressure side of the piston
- Toward the return spring regardless of the design
- Toward the apply pressure side, so fluid pressure presses the lip against the bore (Correct answer)
- The direction does not matter if the seal is lubricated
Correct answer: Toward the apply pressure side, so fluid pressure presses the lip against the bore
Lip seals are installed with the lip facing the pressure, so hydraulic pressure expands the lip against the bore and seals it.
A lip seal seals better as pressure increases, but only if the lip faces the pressure. Installed backward, the seal leaks and the clutch slips. Lubricate the seal with ATF or assembly lubricant and avoid cutting the lip on sharp edges or snap ring grooves. Use a seal installer or protector sleeve where needed. Then air test the piston to confirm it holds.
ASE A2 Friction and Reaction Units
A technician measures clutch pack clearance with a feeler gauge between the pressure plate and the snap ring and finds it greater than specification.
Which correction is appropriate?
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