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Should I be manually shifting due to the low IQ of this transmission?

Discussion in 'Engine, Drivetrain, and Exhaust Discussion' started by KiaStingerNewb, Dec 2, 2019 at 9:34 PM.

  1. KiaStingerNewb

    KiaStingerNewb United States Member

    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?
  2. ecko04

    ecko04 Active Member

  3. KiaStingerNewb

    KiaStingerNewb United States Member

    Someone mentioned maybe I'm not pushing pedal down fully for the click for full boost? I dunno, it just seems inconsistent. Shouldn't be heat soak either because my AIT was down to about 100 tops, which isn't extremely bad. It's been 60 degrees out or so. Lastly I doubt it's the JB4 cutting me back or anything, still in map two and mixed in a bottle of octane booster in case anyway.
  4. StungBlueGT2

    StungBlueGT2 United States 1000 Posts Club! Sustaining Member

    PB Florida, U.S.A.
    This doesn’t sound right at all and our transmissions are similar to the ZF in specs & performance. Mine and every Stinger I’ve driven shifts hard & quick without hesitation and has no problem choosing the correct gear.

    Few questions to get a better idea of your issue.
    Are you in Sport mode?
    Are you in manual mode and certain gear when you punch it?
    Are you pushing the accelerator past the kickdown switch and feeling a “click” at the last 10% before hitting the floor?
    What RPM are you punching it from?

    And using the paddle shifters will shift quicker between two gears, but not when cruising in OD and then flooring it to drop 3-4 gears. Also, its definitely not necessary to use paddles all the time and our transmissions should easily find the right gear and shift very quickly all by itself.
    • Like Like x 1
    • Agree Agree x 1
  5. KiaStingerNewb

    KiaStingerNewb United States Member

    Yes sport mode.

    I'm in D mode not manual.

    RPM not sure.

    Kickdown switch may be culprit. Why the heck do they make it like that? I bet I wasn't hitting it often. I thought I had pedal down, but to trigger I gotta tilt foot forward basically. What is the purpose of it?
  6. Ty Davis

    Ty Davis United States Active Member

    Milwaukee, Wisconsin
    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.
    • Agree Agree x 3
    • Informative Informative x 1
  7. NS_Stinger

    NS_Stinger Canada 1000 Posts Club!

    You could always get a BMS pedal tuner and adjust the throttle to your liking.
    • Agree Agree x 1
  8. StungBlueGT2

    StungBlueGT2 United States 1000 Posts Club! Sustaining Member

    PB Florida, U.S.A.
    I’m not 100% sure but believe the kickdown switch is so you can avoid dropping down a gear while accelerating out of a turn. It allows you to hold a gear so you don’t overpower & spin the rear tires mid turn. Also so while roll racing you can hold the gear at a certain RPM and go 99% throttle without dropping down a gear and losing that split second and momentum.

    However the switch should be subtle as most people have the opposite problem and accidentally hit the switch when they don’t want to drop down a gear, like on dyno runs etc. You shouldn’t have to tilt your foot any differently, it’s just a slight resistance at the last 10% of the accelerator and clicks while you pass it to the floor.

    It might be that, and a combination of the transmission trying to adapt to the additional torque from the JB4. Typically if you don’t have enough available power to accelerate based on throttle input the trans will drop down a gear to assist. However now that you’re running an extra ~100wtq it might believe it’s not necessary to shift down and will hold that gear until more throttle is requested. I’m not clear on how the transmission adapts to additional power vs throttle requests but it’s possible that could be part of the change too.
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