[nicktechla]

Originally Posted by thompstl1

That explanation sounds exactly like what I'm feeling when the transmission "bumps". To support that theory, I've noticed when the car sits for long periods of time it's slow to "grab" going into reverse... waiting for the transmission fluid to be pumped from the pan into the torque converter and transmission.

Actually my Ford truck (F-150 with 6 speed auto) does exactly the same thing

My F-150 6 speed would do it a lot too

[Victoryred1le]

Mine does this too. and sometimes when you rev the car in park it will move the car a tiny bit.(feel it rock) but the car works perfect.

[Walkure]

7700 miles on mine. It's never happened to me.

[Torquem]

I have never experienced this and my car stays parked for long periods of time.

[RealG]

Sounds like this transmission needs an anti-drain back valve in it somewhere. I had this problem on an old C6 ford where the converter would drain back into the pan after sitting especially on an incline and you would have to run it for a little bit for it to fill everything back up. We have not come that far since 1979 it appears. I had a local transmission shop fix it and they said it was something to do with the anti-drain back valve.

[mdmoore23]

My a10 does it. Definitely seems trans related. Haven't seemed to cause any harm though. I just consider it a quirk of the awesome A10.

[TeleZL1]

Originally Posted by mdmoore23

My a10 does it. Definitely seems trans related. Haven't seemed to cause any harm though. I just consider it a quirk of the awesome A10.

This is what I am hoping!

[thompstl1]

Originally Posted by RealG

Sounds like this transmission needs an anti-drain back valve in it somewhere. I had this problem on an old C6 ford where the converter would drain back into the pan after sitting especially on an incline and you would have to run it for a little bit for it to fill everything back up. We have not come that far since 1979 it appears. I had a local transmission shop fix it and they said it was something to do with the anti-drain back valve.

I thought the same thing. My F-150 6 speed has done it since brand new. So bad in fact I videoed how long it took to engage the transmission oafter sitting a couple of days (probably 20 seconds of idle time). The dealer said it was "normal" for this to occur. In honesty, it hasn't got one bit better or worse in 40,000 miles.

In the old days, we would say a transmission that did this had "morning sickness", because it was the first sign of impending transmission problems. Obviously that's not necessarily true anymore!

[ninetres]

Originally Posted by Victoryred1le

Mine does this too. and sometimes when you rev the car in park it will move the car a tiny bit.(feel it rock) but the car works perfect.

I did experience this one time. Tried to rev it for someone that wanted to hear it after I started it. Car would physically load up almost like I was brake stalling it.

[Victoryred1le]

Originally Posted by ninetres

I did experience this one time. Tried to rev it for someone that wanted to hear it after I started it. Car would physically load up almost like I was brake stalling it.

yeah mine does that too. i haven't had any problems, 5500 miles beating the tar out of it making 660 to the ground.

[swizlstik]

Mine has done this since day one.

[camaro5]

Originally Posted by RealG

Sounds like this transmission needs an anti-drain back valve in it somewhere. I had this problem on an old C6 ford where the converter would drain back into the pan after sitting especially on an incline and you would have to run it for a little bit for it to fill everything back up. We have not come that far since 1979 it appears. I had a local transmission shop fix it and they said it was something to do with the anti-drain back valve.

Originally Posted by thompstl1

I thought the same thing. My F-150 6 speed has done it since brand new. So bad in fact I videoed how long it took to engage the transmission oafter sitting a couple of days (probably 20 seconds of idle time). The dealer said it was "normal" for this to occur. In honesty, it hasn't got one bit better or worse in 40,000 miles.

In the old days, we would say a transmission that did this had "morning sickness", because it was the first sign of impending transmission problems. Obviously that's not necessarily true anymore!

Does sound like the TC drains out its fluid, then at start-up it refills.

When the TC gets enough fluid in it to provide the fluidic coupling, the input shaft is then engaged causing a "bump" as internal parts start rotating.

I would check the trans fluid level first.

Originally Posted by Torquem

I have never experienced this and my car stays parked for long periods of time.

So, they don't all do it.

Low trans fluid level?

Variable defect?

Ambient weather differences?

[Gunkk]

Originally Posted by camaro5

So, they don't all do it.

Neither does mine and it's a garaged FL weekend car that sits 5-6 days between starts. My car was not part of the A10 fluid level recall.

[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.