A/T - Grind/Ratchet Noise Shifting Into Park

SOURCE: Isuzu Service News

TITLE: Grind/Ratchet Noise Occurs When Shifting Into Park While in 4 Wheel Drive Low

APPLIES TO: 03-05 Ascender with 4L60E and 4WD

SERVICE TIP:

Reminder:

Ascenders equipped with automatic transmissions and 4 wheel drive may exhibit a condition of grinding/ratcheting type noise when shifting the automatic transmission into park while the transfer case is in 4 wheel drive low (4LO) range.

When in 4LO there is a greater amount of gear reduction through the driveline compared to when the transfer case is in 2WD or 4WD High. When the automatic transmission is shifted from drive or reverse into park with the transfer case in 4LO the driveline unloads and turns the propshaft approximately 1/8 of a turn. This approximate 1/8 turn of rotation will travel into the transfer case through the gear reduction of 4LO, which proceeds into the transmission. The gear reduction in the transfer case causes the transmission output shaft to turn at a greater rate of speed then the automatic transmission parking pawl will hold. This causes the parking pawl to grind and/or ratchet until the output shaft comes to a stop. Grind/ratchet noise will last approximately one second.

This condition should be considered a characteristic of the 4 wheel drive in 4LO. Replacing transmission, transfer case and or driveline components will not resolve the concern. It is recommended to shift into park from the 4HI or 2HI range.