2012 Lexus LS460 Shift Flare when cold

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Good day BITOGers,

My Lexus LS460 with an 8 speed Aisin AA80E transmission with 102,000 miles has a habit of flaring from 2nd to 3rd when the engine has just been started after sitting overnight. The flare is very small (300-500rpm) and it's very smooth. (There is no jerking, slamming into gear etc) Once it's warm it operates normally and I do not observe any slip/flare. The transmission has been serviced (drain and fill completed by Lexus dealer at 82,000 and 98,000 miles) using Toyota World Star fluid.

The strange thing is... When I manually shift through the gears there is no slip/flare at all even when stone cold. ClubLexus has a lengthy thread of over 15 members observing this behavior of all mileages.

What would you guys/gals do in my situation? Thank you for your advice.
 
If it's a common problem, all you can do is drive it easy until it's warm. Maybe, in time, Lexus will offer to fix it. But there will have to be a few total failures for it to get on their radar.
 
The fluid level is probably wrong since the trans shifts fine once warmed up. The fluid level rises once warmed up.

It is difficult to get the fluid level correct- it takes a lot of time and the trans must be cool unless they use the new SST (not sure if that one even works on the 8spd). If you only brought the car in for a drain and refill, the car was probably not in there long enough for the fluid to cool down to <100f - so the fluid level may have been estimated.
 
Originally Posted By: The Critic
The fluid level is probably wrong since the trans shifts fine once warmed up. The fluid level rises once warmed up.


This ^^

My Jeep has the NAG1......also very difficult to get the level right even after a change.
Had the same symptoms as you.
It also took me a while to adjust it to the best level
 
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Thank you all for your kind replies and advice. I will have the level checked next week while it's in service. My last question concerning this behavior is why would I be able to manually shift with no slip? Wouldn't it slip then also? It doesn't.
 
When you say manually shift... You're using a sport mode right? My theory is the transmission is programmed for higher shift pressure when in sport mode. This would make sense for sporty/aggressive driving. You don't want slip when under heavy acceleration.
 
I just reviewed Toyota video on how to check the ATF level. The exercise appears to be something a kid came up with. How does a company with thousands of engineers & scientist, design a AT that is so bleeping sensitive to fluid level. A really dumb setup in my opinion. Ed
 
Maybe it's just botched pressure control logic, something a reflash can [eventually] solve. All those members experiencing the same thing has got to suggest it's not a one-off issue. The flare may not even be from clutchpack or brake-band engagement, it could be as simple as ill-timed TC release for the shift. Some modern autos lockup the TC on even the lower gears, and momentarily unlock/slip it for the shifts. Who knows, but it seems like a logic issue to me.
 
Originally Posted By: SilverFusion2010
When you say manually shift... You're using a sport mode right? My theory is the transmission is programmed for higher shift pressure when in sport mode. This would make sense for sporty/aggressive driving. You don't want slip when under heavy acceleration.


It's off to the side +/- where you can manually push the lever for an upshift and pull for a downshift. In this manual mode there is no slip even when stone cold.
 
Originally Posted By: Eddie
I just reviewed Toyota video on how to check the ATF level. The exercise appears to be something a kid came up with. How does a company with thousands of engineers & scientist, design a AT that is so bleeping sensitive to fluid level. A really dumb setup in my opinion. Ed


Agreed! friggin stupid
 
Toyota made that tool specifically for the FWD 6 speeds, the RWD units don't call for it.

Double-check the fluid level both cold & hot(you need to put the tranny in "service mode" where the D light will be on once you hit the hot check temp or Techstream). Use the check plug, it should trickle if the level is OK.

Wouldn't hurt to see if there's a new calibration/firmware for the PCM.
 
Hello Everyone,

Since my OP I've verified the transmission fluid is filled to the appropriate level. I did another drain and fill (I only get about 3 quarts each time, so far I've done 2 for a total of 6 quarts of fresh fluid). I still notice the slight (300-400 rpm) occasional shift flare only between gears 2-3 and light throttle. Medium and heavy throttle produce smooth and quick shifts.
Anyhoo... If this were your LS, what would you do?

1. Keep driving it and monitor.
2. Perform another drain and fill.
3. Sell it before it worsens.

-Alex
 
If there are no transmission programming updates available, then it is a #1 or #3 situation.
 
Since you already did a drain and refill and check for level, I'd just go ahead and drive it till it is not acceptable and then trade it in. Not sure how much you will get if you sell it right now, but it doesn't look like it will strand you in the middle of nowhere any time soon.

A lowish mileage used transmission sounds like the best strategy when the time arrives.
 
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