hi all,

i picked up a 2018 is 300 f-sport about two weeks ago (2L with the 8-speed trans) for grad school purposes. anyway, the car has about 40k miles on it, a clean carfax and a solid service history.

i have noticed, however, that when the weather is cool or when the car is cool/cold, the transmission sort of bucks very, very slightly when traveling uphill. so generally this only happens in the morning on a relatively steep slope that i currently live by. i took the car to lexus and they were unable to 'replicate the issue' and the issue indeed only happens when the car has been sitting and is cold (i live in southern california, so cold is relative, although high 30s are the outside temps in the morning, albeit the car is garaged). anyhow, does anyone have any suggestions on what to do? i paid for the car outright and i suppose i was wondering if i should just put aside some funds in a separate account dedicated to fixing the car if it breaks but that's the damn reason i bought a lexus for grad school, so that it would be pretty solidly reliable.

i know that servicing these 'lifetime sealed transmission units' isn't really done, but should i have a toyota/lexus mechanic do it anyway?

 

If you have doubts, getting a trans fluid change (drain and fill I think) would be a good thing to try if you think of it as preventative maintenance.

Having said that, I have a 2021 with only 7,500 miles on the clock, and even it has some odd behaviors when cold. Rev flare, occasional hard shift, and sometimes abrupt engagement or jerkiness. If these issues go away when the car warms up, it's probably fine. However, I also wouldn't describe my car as ever "bucking" either. And I live in Georgia, so the temps this time of year aren't too different - we've had plenty of 30-something degree mornings lately.

edit: Also congrats on the new whip!

 

yeah, i think that's what i may do. i'm doing a post-doc fellowship and needed a cheap get-around. i mean, the car is still under bumper-to-bumper warranty but just barely, although the powertrain warranty will still be active for some time.

i don't know if bucking is the correct word. the transmission doesn't really feel quite right, although when looking at the revs during the morning while on an incline there are slight rhythmic blips. it's hard to explain and i'm not sure what is doing what, only that it doesn't feel normal. it doesn't feel like the audi, but perhaps i'm just used to the s4? i dunno.

 

If the ZF in the S4 is anything like the ZF in our 330i, I know what you mean. That trans pretty much always behaves the same way no matter what temperature it is. It's really well-tuned. The only time it ever feels jerky is if I am in manual mode and get on the power right after downshifting. Not sure what's up with that, but even fully-warmed, it still happens. Alas, the Lexus probably is just trying to "save itself" when the fluids are too cold.

 

That jerky feeling could also be a slight engine miss also. It is especially something that would only be felt more so under load like going uphill. Was there not some kind of of reflash update or other Turbo problem others had with this same thing?

 

so, i checked the fluids out of curiosity and the oil was severely overfilled, so i had the vehicle towed to the lexus dealership that i bought it from. they verified that they overfilled the oil and i'm not too sure what repercussions that may lead to, but they changed the oil and refilled to the proper level and handed the car back to me. i did ask to receive documentation that the car was received overfilled and they did comply. it isn't certified, but i don't know if that makes much of a difference right now.

any advice? i did drive the car home and it ran fine. i hope this isn't a nightmare of a purchase.

 

Good find. If it was me, I'd just keep an eye on it. You've got documentation of what the problem was and that it was fixed. Best of luck with it!

 

thanks! hopefully the issue doesn't return/continue. and yes, the zf in the s4 is incredibly well-tuned!

 

I've been complaining about transmission funkiness for a while now on my 2016 200t w/ 8 spd. It has gotten a bit better since I've drained a bit of the transmission fluid that was overfilled.

 

yeah, i'll see if it continues and if it does then i'll have the transmission drained and refilled by a local toyota/lexus shop. i don't want the dealership knowing in the event the trans goes out and i need to use the powertrain warranty.

 

Congrats on the new car!

This happens to my 6 speed as well when car isn't fully warmed up. I live in a slight incline street and the highway near me is slight incline and my transmission jerks or seems to be shift a bit harder until warmed up. Sometimes when going uphill and i let off the gas before turning into my street around 10-15mph transmission almost buckles or gets confused- been happening for awhile even after 3 drain and refills for trans fluid.

I have learned to drive easy on the car when its cold. Once its warmed up car shifts like butter and ready to hit 7200 RPM

 

thanks for the insight -- much appreciated! prior to this IS, i had an is250 like several years ago and the 6-speed transmission was buttery smooth. that whole drivetrain was slow af but buttery smooth, so i was surprised when encountering this problem with the 8 speed. we'll see!

 

Its a different transmission, however, I have a 2018 RC F that does exactly this, and it has done so for my entire ownership period. I also have a 2019 ES 350 that does the exact same thing. As annoying as it can be I’ve just accepted it as normal.

 

Though they are different, I've talked with other F owners and even an LS 460 owner, and they seem to experience some of the same stuff I do. The transmissions are, after all, all supplied by Aisin and set up by Lexus. Heck, for the F and 350/200t transmissions, they even have the same gear ratios.

Having said that, they are different in their calibration and of course are dealing with different vehicles to push around.

 

The way I always saw this 'issue' is that its like a race sequential transmission. Under load at low engine speeds the transmission just bucks. I can't say exactly why or how but the AA80E and AA81E are both pretty much the same design internally except the AA80E has tougher clutch packs (maybe tougher gears too?) and, of course, different logic. So there is a good chance something with the way the transmission is designed is what causes the 'issue'. I personally wouldn't worry about it