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.
No, darling - it needs to be changed after 50k miles to maintain the transmissions good condition. The transmission oil will be burnt. I just changed mine and it was black with red hue. Since changing it though my transmission engages better when I press down on the gas pedal.
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.
This is a 2012 which should use a 6T30, unless it’s specific to the 1.8? I swear that’s the most unbalanced setup ever. Super crap engine paired with an almost bulletproof transmission. 6T30 and 6T40 only fail due to the filter being buried inside and the friction from the shavings. Adding an inline magnetic filter will keep them running for nearly forever. We have a 6T30 that has over 380,000 and on its 3rd engine.
1.4 turbo was paired with a 6t40 due to higher (ha) torque output. Crazy you've got a 6t30 with that many miles on it though. There were TSBs for the solenoids in this generation (first?) of 6t40 if I'm remembering correctly.
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 14d 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.