Trooper II L4-2559cc 2.6L SOHC (4ZE1) (1989)
Transmission Cooler: Customer Interest
A/T - High Pitched Humming Noise
BULLETIN NUMBER
SB91-05-001
ISSUE DATE
May 2, 1991
GROUP
TRANSMISSION
TROOPER II (KT) AUTOMATIC TRANSMISSION NOISE
AFFECTED VEHICLES
Trooper II (KT) models with 4ZE1 engine equipped with automatic transmission.
SERVICE INFORMATION
Some affected vehicles may experience a highpitched humming noise coming from the transmission while driving under load. The noise may be caused
by a miscalibrated oil cooler bypass valve, which is located in the lower valve body.
Installing a new, improved oil cooler bypass valve and spring (see "Parts Information" section of this Service Bulletin) will eliminate the noise.
SERVICE PROCEDURE
1.
Remove the valve body as described in the appropriate Workshop Manual.
2.
Remove and discard the oil cooler bypass valve and spring (Figure 1). Install a new, improved oil cooler bypass valve and spring. See "Parts
Information" section of this Service Bulletin.
3.
Reinstall the valve body as described in the appropriate Workshop Manual.
PARTS INFORMATION
FLAT RATE MANUAL INFORMATION
Use existing Flat Rate Manual labor operation number 051101.