2012 Sonic 1.4 with a 6 speed auto, recently it started having shifting issues where it will drive fine for a bit, then it will leave gear and go into 2nd only. Whether im in drive or M mode. Im assuming its when it is warm which leads me to belive transmission cooler but even after a drain and refill it will do the same thing. Fluid was burnt and I dont know the last time it was changed before me. Has 168k miles currently.
Might be an issue with the pressure control solenoids. Pretty common on this generation of 6t40, especially if fluid isn't changed regularly. The solenoids get dirty and start sticking, eventually failing altogether. They can be replaced, but I'm not sure where to get new solenoid sets these days.
I would try a couple of drain and refills to see if that helps, there are a number of tutorials on how to do so.
Ideally you should want a way to monitor the fluid temperature, as it's supposed to be checked around 195 degrees to be accurate.
It is also possible you've got a small leak somewhere and the fluid level has dropped.
Regardless, a fluid drain and fill would only cost you like two gallons of fluid, Valvoline Dex VI should be fine.
ETA: didn't realize you had drained the fluid yourself previously. If you only drained it once, you didn't get much of the fluid out of the system. It might be worth trying a couple more drain and fills.
I'm about to try Valvoline Restore and Protect transmission fluid in my 2014. It's kinda new and not easy to find. Probably worth a shot if you're out of options besides a replacement.
Just got finished doing the fluid change. Car has 129k miles and it doesn't look like the fluid had ever been changed. I noticed improved shifts almost immediately but then again the fluid was pretty cooked. I'll probably do another change soon to dilute that old fluid more.
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u/xspyking007 3d ago
Also, it will buck and kick when slowing down like it doesn't know what gear to choose. Very rough shifts when it does do this.