Automatic Transmission issue- dealer is not recognizing the issue, please help!

[Arrex]

Originally Posted by James H

I believe the auto boxes in the Lexus IS are the same as the ones in the BRZ. I experienced the same thing when driving my brother's IS350. Shifts are smooth in auto mode but very rough in manual. It jolts you when coming to a stop, almost like someone who can't drive manual well. It gets to the point where you don't want to use the paddle shifters anymore.

:'( such a shame. Does your brother's IS do that in auto mode as well? Mine gives the jerk coming to a stop in both manual / auto mode so it's quite frustrating.

[James H]

No, its fine auto mode. Only gets rough when you use the paddle shifters. Even though the manual shifts are rough in both the IS and BRZ, I find there is a considerable lag in the IS whereas the shifts are almost instantaneous in the BRZ. I am guessing this is just software.

[RZNT4R]

Recent reviews of the Supra lend some weight to the software theory.

The supra uses the ZF 8HP, but unlike every other maker using it who've tuned it for butter smoothness, they've apparently tuned the manual mode to give a kick on upshift. This reminds me of interviews about the LFA, for which they used an SMG rather than a DSG, specifically for the more mechanical feel of the shifts.

But on the other hand, it doesn't account for driver who've felt that behaviour appear after the car had been "normal". I've only driven an automatic once over two years ago before I bought mine, so I can't remember how it felt.

if the cars suffering from the issue have a correct engine load signal, a clean throttle and no fault codes, then it would follow to make sure you're using ATF WS fluid, and if you're driving short trips or are in humid weather and have any significant amount of mileage, to change the fluid, because that stuff absorbs moisture.

[navanodd]

I think I've got mine fixed!

There is still a tiny bit of an idle dip when coming to a stop (sometimes), but its always been there and isn't severe.

Cleaned the MAF, throttle body (a lot better than I did last time) and made sure to leave the car idle for 5-10 mins when restarted to allow the idle re-learn.

Not entirely sure which of those things is what helped, but low RPM performance seems improved along with the idle dip going away.

[James H]

I won't put my money on the longevity or reliability of the ZF transmission. European trannies seem to have way more problems than Japanese ones. I suspect Toyota and Lexus (even the LFA) used Aisin as opposed to DCT for this reason. Getrag makes the notorious TC-SST for the Exo X M and Borg Warner the GR6 for the GTR which have tons of problems. And to me, things like broken shift forks, overheating are just not acceptable. And unlike the Japanese, there is no kaizen culture where they improve the parts and fix the problems for latter model years. The same problems occur in the 2008 to 2014 EXO and the GTR.
My brother had a Saab long time ago and the ZF 4HP18 had well known issues. While Euro trannies are always in cutting edge, they seem to use customers for beta testing. So owning that Supra past warranty may not be something you should think twice about.

[Arrex]

Originally Posted by navanodd

I think I've got mine fixed!

There is still a tiny bit of an idle dip when coming to a stop (sometimes), but its always been there and isn't severe.

Cleaned the MAF, throttle body (a lot better than I did last time) and made sure to leave the car idle for 5-10 mins when restarted to allow the idle re-learn.

Not entirely sure which of those things is what helped, but low RPM performance seems improved along with the idle dip going away.

Nice! When I cleaned my MAF the hard shifting went away for a bit. But came back after ~20 miles. I didn't let it idle however for 5-10 min when restarted so I will try that again.

Interested in knowing if yours is still good until now? Hopefully it didn't go back like mine did

The jerking coming to a stop however I still have no fix

[navanodd]

Originally Posted by Arrex

Nice! When I cleaned my MAF the hard shifting went away for a bit. But came back after ~20 miles. I didn't let it idle however for 5-10 min when restarted so I will try that again.

Interested in knowing if yours is still good until now? Hopefully it didn't go back like mine did

The jerking coming to a stop however I still have no fix

Still seems good. It's a little difficult to be 100% certain, as the weather is getting warmer here. This transmission has never liked cold temps.

[FRSBRZGT86FAN]

Originally Posted by navanodd

I think I've got mine fixed!

There is still a tiny bit of an idle dip when coming to a stop (sometimes), but its always been there and isn't severe.

Cleaned the MAF, throttle body (a lot better than I did last time) and made sure to leave the car idle for 5-10 mins when restarted to allow the idle re-learn.

Not entirely sure which of those things is what helped, but low RPM performance seems improved along with the idle dip going away.

Originally Posted by Arrex

Nice! When I cleaned my MAF the hard shifting went away for a bit. But came back after ~20 miles. I didn't let it idle however for 5-10 min when restarted so I will try that again.

Interested in knowing if yours is still good until now? Hopefully it didn't go back like mine did

The jerking coming to a stop however I still have no fix

Originally Posted by navanodd

Still seems good. It's a little difficult to be 100% certain, as the weather is getting warmer here. This transmission has never liked cold temps.

Sorry late post, I'm the one that originally created the AT software update thread, make sure after you clean it you disconnect the battery for about a minute and turn the key to ON. This clears out the ECU, otherwise the re-learn definitely didn't take just 5-10 minutes, doing this step forces the ecu to relearn.

Also replacing the ATF fluid would probably help with the smoothness issues if any remain.

[Qball1754]

i've started to noticed something like this recently with my 15 fr-s but its coming to a complete stop (at about 10mph) it was really consistent but when i changed my brakes and rotors it got really inconsistent and hopping a full throttle body cleaning will fix this issue