Kia Optima 2.4 2018 - 6sp AT Shift flare when cold - first shift of day

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I was getting this shift flare on the first 1-2 sometimes 2-3 with medium throttle and the first shift of day. Only happened when car sat for a while and temps were 50~F and doesn't happen all the time.

I changed the fluid with Valvoline Maxlife ATF. I thought if I changed the fluid, it would go away. The fluid was pretty dirty for only 30k so I'm glad i did. Around 4qt came out and I put in at least 4.5qt (spillage). Also, the car was already somewhat warm as I had to drive to my parents to use the jack (live in apt). I did the level set at proper temp, etc so I'm pretty sure its not a fluid level issue.

Car only has 30k, so I'm wondering if this is normal operation due to "warm up" or engine running rich. It doesn't happen on light throttle. Anyway, I plan to do another D&F this weekend with around 5 liters. When the car warms up it shifts like a dream, even better than before. Only thing I can think of is the car was underfilled from the factory, and I should've put in a little more. The shop manual calls for 5 liters on a refill then level set.

Looking for insights here. Thanks.
 
Well 5 liters is considerably more than 4 or even 4.5 quarts, so maybe it is still not full?
 
Sounds like temp sensor isn’t right. This is assuming you are correctly checking the fluid level. Engine running in neutral, fill/check plug on pan open, and trans at 135*
 
I used this method to check: http://www.kiopman.com/service_adjustment_procedure-1128.html

and this one says 5 liters: http://www.kiopman.com/replacement-1129.html

I might have waited too long, I don't know. I filled the car and drove it around for 5-10 minutes and came back. Then checked temp and did the P-D-P. I had the temperature gun at the drain bolt but the plastic area where the level plug is was much warmer. However when I pulled the plug there was oil flow.

It might have been low from the factory. It did this even before the fluid change.
 
Has it always done this? Reason I ask is because my ‘18 Sonata has a “shift flare” between shifts and it’s done it since new, only noticeable once the TCC has locked. Also, I’ve experienced this on pretty much every 6+ speed auto transmission, from GM, Ford, Toyota, etc. By definition “shift flare” is bad, but I think when 6+ speeds came on scene with synthetic ATF and clutch to clutch shift engagement, shift flare is a normal occurrence now. Especially now with transmissions that keep the TCC locked during upshifts.

Just my opinion, but have you used any fuel system cleaner lately? If not, I would try a bottle with PEA in it. ECM/TCM calculations are so precise these days based off engine load percentage and a layer of carbon buildup in the combustion chamber can cause the load calculations to be off slightly, causing the ECM/TCM to apply inadequate line pressure or even delayed or early solenoid engagement. GM has a very well known TSB back from the 4Txxe, 4Lxxe transmission days explaining how cylinder head carbon buildup can cause shift flare and other transmission performance issues. A slight engine performance issue can cause what feels like a transmission problem. Just something to to think about. I notice a difference in shift feel after running fuel system cleaner in a car that hasn’t had any in awhile. Most drivers are oblivious to shift flare or other shift feel issues unless there is an obvious jolt or vibration.
 
Has it always done this? Reason I ask is because my ‘18 Sonata has a “shift flare” between shifts and it’s done it since new, only noticeable once the TCC has locked. Also, I’ve experienced this on pretty much every 6+ speed auto transmission, from GM, Ford, Toyota, etc. By definition “shift flare” is bad, but I think when 6+ speeds came on scene with synthetic ATF and clutch to clutch shift engagement, shift flare is a normal occurrence now. Especially now with transmissions that keep the TCC locked during upshifts.

Just my opinion, but have you used any fuel system cleaner lately? If not, I would try a bottle with PEA in it. ECM/TCM calculations are so precise these days based off engine load percentage and a layer of carbon buildup in the combustion chamber can cause the load calculations to be off slightly, causing the ECM/TCM to apply inadequate line pressure or even delayed or early solenoid engagement. GM has a very well known TSB back from the 4Txxe, 4Lxxe transmission days explaining how cylinder head carbon buildup can cause shift flare and other transmission performance issues. A slight engine performance issue can cause what feels like a transmission problem. Just something to to think about. I notice a difference in shift feel after running fuel system cleaner in a car that hasn’t had any in awhile. Most drivers are oblivious to shift flare or other shift feel issues unless there is an obvious jolt or vibration.
Yes, I have ran Chevron fuel system concentrate (black bottle) recently as I bought this car used a few thousand miles ago. The only thing I did not do is pull the negative battery cable which I will try today. I cant replace the fluid again till this weekend.

One other noticeable thing with this car is: once in a while when I start the car after being warmed up, the engine will not rev up expected on initial start. Almost sounds like the car is stalling but its just hovering around 800 rpm. I wrote it off because it only happens once in a blue moon but I get no codes or CEL.
 
Yes, I have ran Chevron fuel system concentrate (black bottle) recently as I bought this car used a few thousand miles ago. The only thing I did not do is pull the negative battery cable which I will try today. I cant replace the fluid again till this weekend.

One other noticeable thing with this car is: once in a while when I start the car after being warmed up, the engine will not rev up expected on initial start. Almost sounds like the car is stalling but its just hovering around 800 rpm. I wrote it off because it only happens once in a blue moon but I get no codes or CEL.
That’s a very common complaint with the Theta II GDI 2.4 and 2.0T. Many people call it a startup “chuggle” with these engines. Mine has done it since new, although some gasoline brands it doesn’t do it. At one point I had multiple colleagues with 2016-2017 Sonatas/Santa Fes and they all did the weird startup chuggle ever since new. We all joked about it in the parking lot when leaving work for the day.
 
That’s a very common complaint with the Theta II GDI 2.4 and 2.0T. Many people call it a startup “chuggle” with these engines. Mine has done it since new, although some gasoline brands it doesn’t do it. At one point I had multiple colleagues with 2016-2017 Sonatas/Santa Fes and they all did the weird startup chuggle ever since new. We all joked about it in the parking lot when leaving work for the day.
Thank you for that comment. I hadn't heard about it. Good to know.
 
Has it always done this? Reason I ask is because my ‘18 Sonata has a “shift flare” between shifts and it’s done it since new, only noticeable once the TCC has locked. Also, I’ve experienced this on pretty much every 6+ speed auto transmission, from GM, Ford, Toyota, etc. By definition “shift flare” is bad, but I think when 6+ speeds came on scene with synthetic ATF and clutch to clutch shift engagement, shift flare is a normal occurrence now. Especially now with transmissions that keep the TCC locked during upshifts.

Just my opinion, but have you used any fuel system cleaner lately? If not, I would try a bottle with PEA in it. ECM/TCM calculations are so precise these days based off engine load percentage and a layer of carbon buildup in the combustion chamber can cause the load calculations to be off slightly, causing the ECM/TCM to apply inadequate line pressure or even delayed or early solenoid engagement. GM has a very well known TSB back from the 4Txxe, 4Lxxe transmission days explaining how cylinder head carbon buildup can cause shift flare and other transmission performance issues. A slight engine performance issue can cause what feels like a transmission problem. Just something to to think about. I notice a difference in shift feel after running fuel system cleaner in a car that hasn’t had any in awhile. Most drivers are oblivious to shift flare or other shift feel issues unless there is an obvious jolt or vibration.
I've only had the car about 3k miles, but it has done this since I've owned it. However, it doesn't always do it. It seems to occur only on literally the first shift of day. After this, it doesn't flare but 1-2 engagement seems "harder" until the fluid is warmed up. After that, its buttery smooth. I filled about 4.5-4.7 quarts but I lost some due to spillage, so it may in fact be low - but when I did the level check it was flowing so I am not sure. I had the car in park, and @Propflux01 mentioned to put it in Neutral.
 
I've only had the car about 3k miles, but it has done this since I've owned it. However, it doesn't always do it. It seems to occur only on literally the first shift of day. After this, it doesn't flare but 1-2 engagement seems "harder" until the fluid is warmed up. After that, its buttery smooth. I filled about 4.5-4.7 quarts but I lost some due to spillage, so it may in fact be low - but when I did the level check it was flowing so I am not sure. I had the car in park, and @Propflux01 mentioned to put it in Neutral.
My 1-2 shift is hard when the tranny is too cold for the TCC to lock. Once the tranny has warmed up the TCC begins locking as normal, and the hard shifts become very smooth.
 
Follow up to this

Refilled around 5.2-5.5 quarts yesterday. I had 2 single quart bottles and a bit less than 3.5 quarts from the previous d&f. The fluid was still very black, quite surprising to be honest. Maybe it was cleaning out the tranny? Don't know.

I was being stubborn and tried to fill without opening the level check port, but there simply isn't enough air flow to easily pump 5 quarts in a reasonable amount of time. The pan takes around 4 quarts with the level check open when it starts dripping. The last quart or so you have to painstakingly slowly pour in while it burps. This time I used a funnel with a hose and it was much easier.

Although today wasn't that cold I did a cold start and it immediately shifted better. No shift flare what soever. Obviously the engagement wasn't as smooth but when I warmed up the tranny I noticed the shifts were even smoother than the previous d&f. I have a hunch the transmission was underfilled from the factory.

The under body cover on the optima is absolutely ridiculous. It's 3 overlapping pieces and u can easily install them in the wrong order. Much easier on the sorrento and other models.
 
We have a 2014 Tuscon 2.4L 6sp auto. It may have the same transmission as yours. Transaxle fluid spec is SP4. dealer only sells SP4-M (synthetic version?) but it is pricey ($20/qt).

I recently bought Valvoline Full Synthetic Maxlife ATF to change the fluid and it lists SP4 and "for high mileage cars" whatever that means and was only $4.40 / qt.

So do you think the low fluid was causing your shift flare and is your spec SP4 also?
How is it doing with the Maxlife ATF?
 
Last edited:
Follow up to this

Refilled around 5.2-5.5 quarts yesterday. I had 2 single quart bottles and a bit less than 3.5 quarts from the previous d&f. The fluid was still very black, quite surprising to be honest. Maybe it was cleaning out the tranny? Don't know.

I was being stubborn and tried to fill without opening the level check port, but there simply isn't enough air flow to easily pump 5 quarts in a reasonable amount of time. The pan takes around 4 quarts with the level check open when it starts dripping. The last quart or so you have to painstakingly slowly pour in while it burps. This time I used a funnel with a hose and it was much easier.

Although today wasn't that cold I did a cold start and it immediately shifted better. No shift flare what soever. Obviously the engagement wasn't as smooth but when I warmed up the tranny I noticed the shifts were even smoother than the previous d&f. I have a hunch the transmission was underfilled from the factory.

The under body cover on the optima is absolutely ridiculous. It's 3 overlapping pieces and u can easily install them in the wrong order. Much easier on the sorrento and other models.
Tll me about it, think they used enough fasteners and 3 different types to boot.
 
We have a 2014 Tuscon 2.4L 6sp auto. It may have the same transmission as yours. Transaxle fluid spec is SP4. dealer only sells SP4-M (synthetic version?) but it is pricey ($20/qt).

I recently bought Valvoline Full Synthetic Maxlife ATF to change the fluid and it lists SP4 and "for high mileage cars" whatever that means and was only $4.40 / qt.

So do you think the low fluid was causing your shift flare and is your spec SP4 also?
How is it doing with the Maxlife ATF?

Do not worry about using max life (red bottle). This works on many many cars. SP4 from hyundai/kia is totally not worth it. When I found out even dealers do not use OEM , I made up mind to use max life. My car had shift flare when cold even before the fluid change, but I replaced roughly the same amount of fluid. I expect it to be fine now. Just follow the service manual and use 5-5.2 quarts. Also try to change cold, I changed hot and that is why I think I got more out but it really doesn't matter. I think I was a half quart or so low maybe more if it was underfilled to begin with. Car shifts like a dream no regrets after filling correct amount. Accounting for spillage u might want more than 5qt on hand.
 
Thanks for the info!

Last time I used dealer SP4-M at 50K or 60K miles. I think I paid $16/qt for it few years ago. Didn't want to risk any warranty issues just in case ...

car just went over 100K miles and the warranty ends at 100K miles so I decided to use Maxlife but was a little concerned since maxlife lists bunch of other specs/approvals as well ...

I use maxlife in our SP3 atf car and it's been doing great.
 
I took my car out for a long drive. The car never shifted this smooth warmed up, even before or after the first drain and fill. And keep in mind this car only has around 28k. This leads me to believe either the fluid was still substantially dirty or the atf was underfilled, probably the latter.
 
The 6-speed Hyundais that I've owned did not have any cold shift flare. And, none were ATF picky.

My only recommendation is to make sure you use a scantool for ATF temps since IR guns, without calibration, can be off some.

Older 6 speeds has some wiring harness and temp sensor replacements since it was a known defective part. I doubt it would be an issue with newer transmissions unless you have a CEL calling it out.

I'd perform 3 back to back drain/refills, obviously with a 10 minute ride in between each, set the proper level, and see how it does.

If it still flares and you used Maxlife, I'd switch back to OE or equivalent fluid from Ravenol, Aisin, BeckArnley, Idemitsu...

The other option is to dump Maxlife for any other competitor full synthetic LV HFM fluid. Amsoil ATL, Redline D6, Lubegard, Pennzoil... are some competitors. Sometimes its not the best idea to shop fluids on price only.
 
The 6-speed Hyundais that I've owned did not have any cold shift flare. And, none were ATF picky.

My only recommendation is to make sure you use a scantool for ATF temps since IR guns, without calibration, can be off some.

Older 6 speeds has some wiring harness and temp sensor replacements since it was a known defective part. I doubt it would be an issue with newer transmissions unless you have a CEL calling it out.

I'd perform 3 back to back drain/refills, obviously with a 10 minute ride in between each, set the proper level, and see how it does.

If it still flares and you used Maxlife, I'd switch back to OE or equivalent fluid from Ravenol, Aisin, BeckArnley, Idemitsu...

The other option is to dump Maxlife for any other competitor full synthetic LV HFM fluid. Amsoil ATL, Redline D6, Lubegard, Pennzoil... are some competitors. Sometimes its not the best idea to shop fluids on price only.

My personal opinion is all the low viscosity fluids are similar. This is not a regular change interval like engine oil so the oems can get away with specifying OEM only in their manual. The fluid is "lifetime" after all. Reading that most shops don't even use OEM and the reviews online, I didn't want to spend. I would have considered trying a different fluid but this was happening with the factory fill. It makes sense as the fluid expands it smoothed and that the fluid was low. The problem was the first time I spilled alot so even with 4.5qt in, it was probably just around 4, about what came out.

The temp gage thing is plausible as I'm using a harbor freight gun. Can you recommend a scan tool that doesnt break the bank that does atf for different cars? Looking to do this change on my gf Toyota which seems more difficult. Thanks!
 
Plenty of good used scantools on ebay.
Verify it can read your year/make/model ATF temp by contacting the manufacturer prior to bidding.

My Hyundai/Kia ATF is read with a Hyundai specific app and a generic obd port bluetooth scanner. Problem is, the software has not been updated in ages and doesn't work with some newer models. I used one of the 'programable common overhyped apps' for Toyotas with the same obd tool. But, I had to program the PID's and it takes a while to find the one that works. Again, its year/make/model dependent. But, most Toyota's can still use the SST(jumper wire two of the obd pins) to put the 'dash lights' in ATF level check mode.
 
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