Transmission Issue with Liberty GT 2010 AT

[aertey]

Hi, I own a Liberty(Legacy) 2010 GT with an automatic transmission and have been having this issue for the past couple of months. Occasionally when accelerating from a stop or very low speed, the transmission would rev up high without delivering power and suddenly jerk into gear, making a loud clunk sound and jerking the car forward heavily. I've taken it to a couple of mechanics but none could find the issue. No codes have been posted and could be found. I've tried resetting all the car's electronics but nothing seems to fix the issue. The trans fluid was changed around a month ago when I first started having this issue as I thought it would solve it but to no avail. I've got dashcam videos of times when it has happened and have linked them below. You can hear the car revving up before the car forces itself into a new gear. I'm at a dead end here and don't know what to do. Any suggestions?

Video 1: https://drive.google.com/file/d/1X08Ko9xJ4I0v1WZBwvMoNLUDO0s0H4os/view

 

Video 2: https://drive.google.com/file/d/1dgJpqu5ih5y9q5O4ZSMJPFVAhrjVcgcg/view

 

[NVAKeith]

I was going to direct you to an Outback forum as you’ll find a lot more 5EATs in the 3.6R Outbacks…but I see you’re already there

https://www.subaruoutback.org/threads/subary-liberty-legacy-transmission-issue.566088/

[Scubaboo]

The most common culprit I've read for sudden abrupt shifts like that is the transmission valve body.  Specifically a malfunctioning speed sensor on the valve body.

Replacing the entire valve body is the usual fix.  Sensor itself not available from Subaru but generic replacements are available online and been tried, though I've read a few reports of the problem returning and having to get a new valve body to fully resolve.

 

[Alexmed2002]

1 hour ago, Scubaboo said:

The most common culprit I've read for sudden abrupt shifts like that is the transmission valve body.  Specifically a malfunctioning speed sensor on the valve body.

Replacing the entire valve body is the usual fix.  Sensor itself not available from Subaru but generic replacements are available online and been tried, though I've read a few reports of the problem returning and having to get a new valve body to fully resolve.

 

There were also issues with the torque converters too, so that's another thing to check.

[Scubaboo]

7 minutes ago, Alexmed2002 said:

There were also issues with the torque converters too, so that's another thing to check.

Oh yes, that too!

[aertey]

8 hours ago, Scubaboo said:

The most common culprit I've read for sudden abrupt shifts like that is the transmission valve body.  Specifically a malfunctioning speed sensor on the valve body.

Replacing the entire valve body is the usual fix.  Sensor itself not available from Subaru but generic replacements are available online and been tried, though I've read a few reports of the problem returning and having to get a new valve body to fully resolve.

 

 

6 hours ago, Alexmed2002 said:

There were also issues with the torque converters too, so that's another thing to check.

Ahhh exactly what I was hoping against. I've been reading some other similar forum posts and have seen some people have some luck with clearing memory 2 and relearning the TCU. Might give that a try before opening up the trans. Thanks for the help!

[Scubaboo]

On 4/26/2024 at 4:05 PM, aertey said:

 

Ahhh exactly what I was hoping against. I've been reading some other similar forum posts and have seen some people have some luck with clearing memory 2 and relearning the TCU. Might give that a try before opening up the trans. Thanks for the help!

Yes, do definitely try that first, or maybe checking with a dealer if there is an updated TCU flash?

[Humble Rumble]

In addition to the TCU, the valvebody, and the torque converter, I would also say it's not at all a bad idea to inspect and likely replace the rear engine/trans mounts. I say "engine/trans" mounts because the rear engine mounts are actually physically located on the transmission bell housing itself. When I did my first engine change, I installed new stiffened Kein mounts, and it 100% completely eliminated my low gear shift-shock, and also made it so that I can downshift all the way to 1st without any strong jolts. It also made the acceleration feel insanely direct and like it just never stops pulling. 

Granted, the Kein mounts introduced a lot of NVH to the cabin, so I wouldn't recommend those mounts for a daily driver, but fresh OEM mounts will still have a similar affect on the shift characteristics. When you consider that even if the mileage is super low, the rubber in the mounts is roughly 15 years old and likely suffering from a fair amount of age fatigue regardless. 

Part # 41022AJ040, need 2 of them. Labelled "41020" in this diagram.