4L60E/4L65E/4L70E Snap Noise 2-1 Downshift - keywords clunk

This PI is being superseded to update model years, conditions and instructions. Please discard PIP3106A.

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

1999-2007 light duty trucks, passenger cars, and utilities equipped with the 4L60E (M30), 4L65E (M32) and 4L70E (M70) automatic transmissions may experience a single snap noise during a 2-1 downshift when coming to a stop.

The snap noise should not be confused with a stop clunk as it is a snap. The snap noise may be described as a ball peen hammer hitting the transmission case. The noise may also be present when shifting from reverse to drive or drive to reverse. The snap noise may appear to be coming from the transfer case.

The Low and Reverse Clutch Support Retainer Spring (anti-clunk spring) (item 680) may have been bent during the production process the noise will most likely occur at low mileage (0 to 7500). If the noise occurs at a higher mileage the spring may have been bent or omitted during a recent repair or is worn.

The Low and Reverse Clutch Support Retainer Spring (item 680) should be inspected for being bent or missing. If damaged or missing, replace the spring.

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.