[camaro5]

Originally Posted by 17RHZL1

#08-07-30-026E: Information on Slight Vehicle Movement in Park at Start Up After Cold Soak - (Dec 12, 2017)
Subject: Information on Slight Vehicle Movement in Park at Start Up After Cold Soak

Models: 2018 and Prior GM Passenger Cars and Light Duty Trucks
Equipped with Automatic Transmission
Attention: This Bulletin also applies to any of the above vehicles that may be Export from North America vehicles.
This Bulletin has been revised to add the 2018 Model Year. Please discard Corporate Bulletin Number 08-07-30-026D.

Some vehicles may rock or move slightly forward or rearward while in Park at start up after cold soak. This condition may be accompanied by a clunk noise. This is a slight movement that is more often seen visually, rather than felt, when viewed from the outside and using the auto-start feature, if equipped.

This slight movement is due to the residual transmission fluid in the clutch packs that creates a partial apply on start up. This movement is stopped by the parking pawl and/or transmission fluid exhausting completely from the clutch packs.

This condition is normal and no repairs should be attempted. This can be verified by comparing with another identically built vehicle under the same cold conditions.

I was going to add that any motion in park indicates one or more clutch packs not fully disengaged.

So, count on the parking pawl to hold back the vehicle.

Those grabbing half engaged clutches are wearing and depositing friction material into the trans fluid.

Might not impact performance if it doesn't happen often.

No comment on the engineering and testing.

l

[Pwiegand]

Mine has done this exactly 3 times so far, twice while still warm and one of those times while parked on a nose down incline. 5000 miles.

[str8naro]

mine has this symptom more often than not.has anyone confirmed that this is "normal" with GM? its really the only thing about the car i don't like