I was under the impression that it's faster to just let the transmission find a gear, but a lot of times I'll punch it from a roll (say 50 mph) and the car just stays in a higher gear it seems and the RPM needle moves like a slug. Then other times it pulls like a train from a roll. I can only assume this is the brain of the transmission. The ZF masterpiece in a lot of cars right now doesn't have this issue. It ALWAYS finds the right gear, and very quickly. I wish there was a way for the JB4 to control shifts (or is there and I'm missing it?). This transmission is well built apparently in terms of durability, but it's also dumb it seems. Basically the transmission is an NFL offensive lineman, the ZF is a trained assassin.
Is it faster to take control of the shifts instead all of the time?
My previous 3 vehicles were BMW 3 and 5 series with the ZF6, ZF6 Sport Auto, and ZF8 Sport Auto.
The Stinger Tranny is well sorted and programmed in my experience.
It shifts smoother than the ZF8 SAT in my last 535i.
It also picks the right gear every time (so far).
The ZF8 does beat the Stinger in a few areas...
The ZF8 has quicker reactions to manually induced shifts (
paddles).
The ZF8 has shorter shift times too.
That being said, the Stinger Transmission is close in these areas, still very good, just not as fast as the ZF.
The ZF could be caught a gear too high sometimes when accelerating from a roll at neighborhood speeds.
My Stinger did experience two abrupt downshifts on the highway while passing when the car was brand new. It’s been perfect ever since then in this regard. A Stinger issue that is persistent though, is the transmission will allow the car to roll backwards while shifting between reverse to drive on a steep incline. There is a momentary pause in power that will let the car roll back a bit (more than other cars).
Anyway, on to your issue...
Could your JB4 be causing an issue?
Do you still have this issue with the JB4 bypassed?
Another thing, are you aware of the maximum speed ranges for each gear?
1st will take you to a certain mph/rpms, and 2nd, 3rd, etc. has a max limit too.
What you will notice is that the Stinger is programmed not to redline in 1st gear.
1st gear (in auto mode) will not take you to redline. The tranny will short shift.
This is done (in my estimation) to preserve components from damage/wear that might make Kia have warranty claims. Experiencing the car, there seems to be more than a few areas that have been tamed to protect that warranty.
Similarly, there is a maximum speed at which you can downshift into a lower gear too. Here again, the computer won’t downshift to a gear that puts you too close to redline. There is a buffer of several hundred rpms, that serve to protect the drivetrain. If a requested downshift would exceed this buffer (or the redline itself) it won’t shift down to as low a gear as you expect and your acceleration will be muted because of it.
Watch your rpms/mph/actual gear/expected gear when you are experiencing this lack of pull and power and you will probably find that you are too close to redline to get the gear you expected and got a higher gear instead. When you ask for maximum acceleration in this range, it can feel softer than expected. It’s not due to a lack of power, but simply because you are accelerating in a higher gear. Manually shifting does have the benefit of shrinking the range of this rpm buffer allowing you to get the acceleration you request and expect more of the time.
More... let’s assume that everything is all good with your JB4 and what you are experiencing is an actual problem.
It would be a good idea to reset some vehicle adaptations.
The ones you want are the Throttle Body Adaptation reset and the Automatic Transmission Adaptation Reset.
This will allow your tranny and throttle body to start from scratch in storing their operating data.
This can cure all sorts of drivability issues. Any scantool can do this.
I am not aware of any way to do it without a scantool on this particular vehicle.
Keep us posted on what you find.
