My 2.0 AWD blew a transmission in March 23. I noticed a small shake/ vibration when turning the car on and putting it in gear immediately after buying it used in October 22. The vibration would happen when the car was completely cold after sitting all night and I put in it Drive or reverse while staying on the brakes. The small shake turned into the whole car violently shaking from a cold start for about 20 seconds and then would stop after the trans got to operating temp. Other issues I had as the trans decayed was the car holding and slamming low end gears. That could be potentially similar to what you're experiencing.
However, I have a question, how immediately after the initial incident did you have the TCU reset and how long has it been since? I personally would have recommended against getting it reset as now you cant accurately keep track of any changes in the way it drives. Now the car needs to relearn your driving for a few hundred miles. When I got the new trans it was clunky and it took several hundred miles of slow calm driving and slowly getting more and more on throttle to bring it back to nice smooth shifts.
If it only happens in Comfort its likely that the car is still learning your driving. If it was a trans issue I would think that sport mode would also have the issue occur. Sport mode is when the car is under its most extreme conditions of acceleration and shifting, comfort mode at 1500 rpms seems like software over hardware. I know in my car if I drive in comfort mode and am really laxed with my driving for an extended time and all of a sudden I floor it and then cut throttle almost as quickly, the car has no idea what I want it to do and it spazzes trying to pick which gear I want for the acceleration I need. In that case the car cuts power as to NOT damage the Transmission between shifting gears, if you gun it while rolling in 6th gear and it tries to jump down to 2nd and then you cut throttle as its shifting it wants to choose a different gear halfway through shifting which is why you might have experienced that " as if I was driving in neutral". If you blow a trans and it would likely get replaced under factory warranty.
I am in no way close to a mechanic so take what I say at face value, just my two cents from dealing with my trans issues.
Most important take aways
- Give it time and keep note of any actual changes in sounds and especially changes to driving feel. If its an issue it'll get worse slowly, it should not just instantly blow up
- That "thud" you hear might just be in your head. I know as my car got worse and even after it got fixed I worries about any inconsistent sounds or feels that usually amount to nothing. Generally the stingers transmission has held a good reputation as of what I know even with stage 2 tunes.
-If you have a warranty (1st or 2nd owner) it should be 100% free if it is a Transmission issue. If you have
mods on the car and really think its the transmission I would remove any if you plan to get it properly looked at. Kia requires picture documentation of the engine bay as well as TCU data for warranty claims.
