Grind/Ratchet Noise Occurs When Shifting Into Park While in 4 Wheel Drive Low - keywords case shift transmission transfer

This PI is being superseded to update models and years. Please discard PIP3366.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Light Duty Trucks 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 transfer case into the driveline then 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 turn. This approximate 1/8 turn of rotation will travel into the transfer case through the gear reduction of 4LO and into the transmission, the gear reduction in the transfer case causes the transmission output shaft to turn at a greater speed then the automatic transmission parking pawl will hold. This will result in the parking pawl to grind/ratchet until the output shaft comes to a stop. The grind/ratchet noise will last approximately one second.

This condition should be considered characteristic of 4 wheel drive vehicles operated 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.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.