Century Estate Wagon V6-231 3.8L (1985)
Clutch: All Technical Service Bulletins
A/T - 1-2 Slip or Shudder, 2nd Gear Slip, or No 2nd Gear
Bulletin:
90-7440-11
Date:
May, '90
Ref. No.: 90-119-7440
Corp. Ref. No.: 077113R
SUBJECT:
440T4/4T60 DISTRESSED SECOND CLUTCH DIAGNOSIS INFORMATION
MODELS AFFECTED: 1984-1990 CENTURY, PARK AVENUE/ELECTRA, RIVIERA, LESABRE, AND REGAL
Second clutch diagnosis tips - all 1984-90 Hydra-Matic 4T60 (THM 440T4) transaxles.
A worn or damaged second clutch in a Hydra-Matic 4T60 transaxle may exhibit one of the following conditions.
1.
Slips or shudders during 1-2 shift
2.
Slips in second gear
3.
No second gear
When diagnosing a transaxle for one of the above conditions, the following items should be checked first.
1.
Test drive the vehicle to verify the condition.
2.
Verify proper fluid level.
3.
Verify proper transmission line pressure according to the chassis service manual procedure. Check minimum pressure by applying 18" of vacuum
to the vacuum modulator (use a hand vacuum pump). Check maximum line pressure with no vacuum applied to the vacuum modulator (vacuum
line disconnected). Check both minimum and maximum at 1250 rpm in each range. If there is no boost in pressure with zero vacuum, check for an
inoperative vacuum modulator or modulator valve. A ruptured aneroid bellows in a vacuum modulator will result in no boost in pressure with zero
vacuum applied.
Note:
Do not measure maximum pressure by pulling out on the T.V. cable. 1987 and later models will give you a boosted pressure at full
T.V. which is not the same as the maximum pressure reading with zero vacuum. Using the T.V. cable can give you a false maximum
pressure reading and will not reveal an inoperative vacuum modulator.
4.
Use a vacuum gage on the vacuum line at the vacuum modulator end to verify full engine vacuum is available at the vacuum modulator. The
vacuum should register immediately as the engine is started and should respond quickly to engine load changes. When you flash the throttle from
idle, the vacuum gage should drop instantly and recover as soon as the engine returns to idle. If the response is slow, check for a restriction in the
vacuum line. This restriction can trap vacuum in the modulator on acceleration and cause a slip during shifts because of low boost pressures.
Remember that 1989 and 1990 Regals with 3.1L engines have a .031" orifice in the modulator end of the line. Do not enlarge or remove this
orifice.
Knowing the results of the above checks will help determine the causes of a damaged second clutch once you get inside the transaxle. The second clutch
is applied and carrying torque in 2nd, 3rd and 4th gear. Therefore, if fluid level or pressure is low or if the pressure does not boost when the engine is
loaded, the 2nd clutch will be one of the first to slip and eventually wear or burn.
Once inside the transaxle there are several items to look for when diagnosing a damaged 2nd clutch:
1.
Mispositioned 2nd clutch snap ring
2.
Split, cut or rolled 2nd clutch piston seals or damaged piston
3.
2nd clutch housing leaking through cracks in the housing or welds
4.
Fluid leaks through 2nd clutch housing check ball or its retainer
5.
Check for deformed or damaged piston return springs in the apply ring and return spring assembly. If these springs are weak, they can allow the
2nd clutch plates to drag while the 2nd clutch is released in 1st and reverse. This can result in premature wear of the 2nd clutch plates.