9000 L4-1985cc 2.0L DOHC (1986)
Fluid Line/Hose: All Technical Service Bulletins
A/T - Resonating/Moaning Noise
FILE IN
VOL.
I
S.I. Man.
SEC.
B-4
PG.
25
Issue:
11/89-1194
Subject:
Noise from ATF Cooling System
Application:
9000 Models with Automatic Transmission
Some 9000's equipped with automatic transmission may develop a resonant noise in the automatic transmission fluid (ATF) cooling system that can be
heard inside the car. The noise arises from pressure pulsations in the cooling circuit that cause the thermostatic valve to vibrate. The noise can be
compared to a turbine whine, a moan, or a bearing noise. Although the noise does not create any functional or reliability problems in the transmission,
some customers may find it to be objectionable.
The amount of noise is influenced by the amount of air that is present in the ATF.
^
Excess air can be whipped into the ATF if the transmission is either under filled or over filled.
^
The age of the ATF can affect its air content since the anti-foaming additives of the ATF can break down over time, especially under severe
operating conditions such as city driving or trailer towing. Cars being driven under severe conditions should have the ATF changed every
15,000 miles.
The noise primarily affects cars operated in hot climates or during hot weather. The car must be driven long enough to heat the ATF up to the
temperature where the thermostatic valve opens. The pitch of the resonance is dependent on the engine speed, so that as the engine rpm's increase the
pitch also increases. When the transmission shifts to the next higher gear, the pitch will decrease at the shift point and then increase again as the engine
speed increases.
To eliminate the noise, service kits for both turbo and naturally-aspirated models are now available. Each kit contains two newly-designed ATF cooling
system hoses that replace the thermostatic valve and the four current hoses. See below for complete repair information.
NOTE
Replacement of the transmission will not correct a thermostatic valve noise complaint. Non-defective transmission units returned for this complaint will
not be accepted under warranty.
Parts Required:
ATF Hose Kit, Turbo
41 18 881
Seal ring (as needed)
89 81 961
Kit Contents
^
Hose, supply 40 28 874
^
Hose, return 40 28 890
^
Double stand-off clamp 73 98 464
^
Single stand-off clamp 75 93 221
ATF Hose Kit, normally-aspirated
41 18 899
Seal ring (as needed)
89 81 961
Kit Contents
^
Hose, supply 40 28 882
^
Hose, return 40 28 890
^
Double stand-off clamp 73 98 464
^
Single stand-off clamp 75 93 221
Diagnosis
