Two technicians are evaluating a shudder on engagement of the lock-up clutch. Which statement is correct about the potential causes?

Two technicians are evaluating a shudder on engagement of the lock-up clutch. Which statement is correct about the potential causes?

• A. Technician A
• B. Technician B
• C. Both Technician A and Technician B
• D. Neither Technician A nor Technician B

Answer: (B)

Shudder during lock-up engagement happens when the clutch doesn’t grab smoothly, so the torque transfer is uneven as the torque converter lock-up clutch engages. The most common causes are problems with the friction surfaces themselves, contamination or degradation of the transmission fluid, and issues in the hydraulic control that apply the lock-up clutch. If the friction material on the lock-up clutch pack is worn or glazing, engagement can grab and slip repeatedly, producing a shudder. Fluid that’s dirty, burnt, or outside the correct viscosity can alter the friction characteristics and cause grabbing or slipping as the clutch engages. Hydraulic issues—such as insufficient, fluctuating, or delayed line pressure when the TCC is commanded—can also make the engagement feel abrupt or jerky. The statement that correctly identifies plausible, testable causes is the one that aligns with these realities: symptoms consistent with friction wear, fluid problems, or hydraulic pressure irregularities, rather than attributing the shudder to unrelated or unlikely causes. To verify, check the transmission fluid (level, condition, and contamination), inspect the lock-up clutch components for wear, measure line pressure during TCC engagement, and review the TCC solenoid/valve operation. If fluid is degraded or the clutch pack shows wear, service accordingly; if hydraulic pressure is off, adjust or repair the hydraulic circuit.

Shudder during lock-up engagement happens when the clutch doesn’t grab smoothly, so the torque transfer is uneven as the torque converter lock-up clutch engages. The most common causes are problems with the friction surfaces themselves, contamination or degradation of the transmission fluid, and issues in the hydraulic control that apply the lock-up clutch. If the friction material on the lock-up clutch pack is worn or glazing, engagement can grab and slip repeatedly, producing a shudder. Fluid that’s dirty, burnt, or outside the correct viscosity can alter the friction characteristics and cause grabbing or slipping as the clutch engages. Hydraulic issues—such as insufficient, fluctuating, or delayed line pressure when the TCC is commanded—can also make the engagement feel abrupt or jerky.

The statement that correctly identifies plausible, testable causes is the one that aligns with these realities: symptoms consistent with friction wear, fluid problems, or hydraulic pressure irregularities, rather than attributing the shudder to unrelated or unlikely causes. To verify, check the transmission fluid (level, condition, and contamination), inspect the lock-up clutch components for wear, measure line pressure during TCC engagement, and review the TCC solenoid/valve operation. If fluid is degraded or the clutch pack shows wear, service accordingly; if hydraulic pressure is off, adjust or repair the hydraulic circuit.