Hi pngo,
Even in manual mode too?

Well a reflash would be great, but IDK whether is it available upon request.

 

In manual mode, I still feel shifting between 2nd to 3rd and 4th to 3rd to be harsher but a lot less noticeable.
Last time I asked, there was no reflash available for my 2016 IS. I do not expect that a reflash for 2017+ models to work on a 2016 model, assuming there are other differences in the code not relevant to the older models.

 

I've been experiencing this problem lately with a lag/slight jerk from 2nd to 3rd in my 15' IS350 (70K mi) with the same transmission. Did you figure out what the issue was? To add on to the original post, if I shift from park into drive too quickly, the car makes a boom sound. Not sure if this is all related.

I know our transmissions are sealed with lifetime fluid, but is a trans flush recommended? Perhaps solenoids? Is this something to ignore?

 

It seems I've managed to narrow down the problem (2nd to 3rd lag): it arises only when the oil in the transmission is still cold (below approx 100F/38C).
After oil change it remained the same. Mileage is 31k. Even in D I can feel a break in the acceleration during the upshift from 2nd to 3rd,
while the engine revs up a bit until the 3rd gear engages, and the accelerator position is the same.

The phenomenon vanishes as soon as the oil / trans temp gets warmer.

 

I think you're right because I've noticed that also. It smoothens out as you drive more but sometimes I do get it even when warmed up. You said even with new trans fluid, the problem remained?

I spoke with an independent shop and they said to ignore the problem and that it wasn't anything.

One thing to note is I did notice the gear shifting after installing a new battery,. It could be that, although it's been 2 weeks since it was installed. The booming sound I get when going into D too fast has been there for quite some time

 

Yes, the experience remained the same after transmission oil change.

After battery change the transmission needs a short adaptation.
It usually requires a few rounds "around the block" allowing the transmission in D position to engage
all gears from 1st to 8th, and back using only the enginebrake.

The booming is usually a resulted by the high idle right after starting up the engine,
engaging 1st gear will put a higher strain to the drive-train, forcing/slamming the shafts with higher force against the brakes.

 

Are you doing all this before all Engine oil & ATF fluids are not at proper operating temps ??


@lobuxracer


Joe Z

 

I've chalked up most of the weirdness with this trans in my IS 350 to be because of fluids not being up to temp as well. I've even noticed some rev flare and/or roughness shifting from 2nd to 3rd on cooler days (i.e. around 40-50 degrees F). It goes away after a few minutes of driving.

If at operating temp and issues persist, then it might be time to try changing the fluid or otherwise troubleshooting.

 

Check battery! Higher than "S95 EFB" make sure EFB if you use Auto-stop. it will fix jerky transmission.

 

Are you referring to auto-start-stop of the engine? IS350 models don't have this.

 

you can check battery health. Not just voltage. Even if it shows 12.6v sometimes it can't hold the voltage for longtime. Weak battery will steal the power from alternator.
and it will affect solenoids inside of tranny for sure. Do the cheapest one first. Peace.

 

ever find anything to ease the hard 2/3 shift during cold start?

 

When the traffic conditions allow, I'm throttling back almost fully when the speed reaches the shifting threshold. This helped me to reduce or eliminate the harshness.
I find this awful in the microprocessor era, when dynamic adjustment of the shifting characteristics (based on the oil temperature) shouldn't be an issue.
Also this is unworthy for Lexus: what kind of driving experience is this?

 

If you didn't have this 2-3 shift issue before, I'd personally still be trying to fix it if I were in this situation.

However, even my brand-new 2021 IS 350 was exhibiting some odd 2-3 shift behavior. Once, I left it parked over the weekend at my brother's townhome, which has a pretty steep side street to get out to the main road from it. This was back in April when it was still fairly cold, so the car was definitely cold. When I left, I proceed to drive up this hill, and I got a gnarly 2-3 shift. Like, a full-on jerk. Normally, when the car is cold I expect some rev flare and maybe I can "feel" the shift, but not like this. I almost got concerned about it, but it's never happened again. I could be low on transmission fluid, but also, it is par for the course for these cars to do things like this.

 

I have this issue since I bought the car, which was two and half years old then with 15.5k miles in the odometer. I've requested transmission fluid change in the dealership, but no change in the issue (if they really changed the fluid...). The transmission case has no leaks. The car is usually sits in underground garage during the night, not exposed to temperatures below 55F. Despite this I'm still experiencing the lag, and after approx. 5 minutes it goes away. It took me some time to find the relation between the temperature and the jerkiness between 2nd and 3rd.
This makes me think that this is a design flaw in the transmission control software, which doesn't deal with oil temperatures below 100F, especially I'm not the only one who experiencing this. The issue affects many 3rd Gen IS-es through the manufacturing years.

I'm not saying that I can't live with this problem, but it's annoying.