Sonata V6-3.0L (1991)
Clutch: Technical Service Bulletins
A/T - Damper Clutch Operation
Group: TRANSAXLE
Number: 96-40-017
Date: SEPTEMBER, 1996
Model: ALL w/AUTOMATIC TRANSAXLE
Subject:
AUTOMATIC TRANSAXLE DAMPER CLUTCH OPERATION
DESCRIPTION:
On vehicles equipped with automatic transaxles, a customer may complain of feeling what seems to be a sudden and seemingly inappropriate downshift
when traveling at a constant speed under light load (level terrain). The customer feels the Damper Clutch disengage, which is a normal operating
characteristic and no repairs are necessary.
OPERATION:
The Damper Clutch will engage ("Lock-Up") only when all of the following conditions are met:
^
Transaxle is in 2nd, 3rd or 4th gear.
^
Automatic transaxle fluid (ATF) temperature is greater than 158° F (70° C).
^
Relationship between the torque converter turbine rpm and throttle opening are within a specified range.
At a constant speed cruise under light load (level terrain), the ATF temperature can drop below 158° F (70° C) causing the damper clutch to disengage.
This disengagement causes the engine speed to increase 200-300 rpm and may be described as a "downshift" sensation. Typically, the ATF will heat up
rapidly and the damper clutch will re-engage. Re-engagement is very smooth and normally not felt. If the vehicle maintains the constant speed cruise
under light load it is likely that this condition will repeat. Damper clutch disengagement is a normal operating characteristic and no repairs are required.
VERIFICATION:
Damper clutch disengagement can be diagnosed and verified by temporarily disconnecting the ATF temperature sensor. With the temperature sensor
unplugged, the TCU thinks the ATF is staying below 158° F (70° C) and will not command the damper clutch to engage. If this eliminates the described
"downshift" sensation, reconnect the temperature sensor and explain the system's operation to the customer.
