I realize there are other threads on this but this case might be a little different.
2008 LS460L
209,000 miles
No maintenance history on Carfax or Lexus

The transmission shifting quality is about 8/10. About 80% of the time, the car shifts normally. 20% of the time it's a little hard to explain other than saying the car shifts a bit rough.. or not at the normal time with there being a little delay..
When going from P to R, it takes about a half second and then goes hard. It;s the same when going into D.
When flooring the car from zero, there's a VERY SLIGHT clunk I can feel in the pedal just before taking off and shifting normally.
Transmission used to slip and roll very rarely but that seems to have stopped recently. I'm not sure why.

I have 6 quarts on the way,.. should i flush out 6 quarts or all 10.6 ??
or if I should drain and fill.
or if I should just leave it alone..

Assuming the transmission were to be destroyed my plan would be to sell the car as is or replace the transmission w/ a junk yard donor. How hard can it be if teenagers on youtube can do it ?

Thoughts ??

 

Not advice. If that was my car I'd replace all the ATF with Amsoil. If you want to find out what it's like to pull a transmission go to a help yourself salvage yard and go at it.

 

Before replacing the fluid, inspect it. If it is too dark, there could a be risk that transmission will stop working die to the fluid containing friction material necessary for the transmission to function. Transfer of friction material from clutches to the fluid happens over time and goes faster when the fluid gets older.

 

Drop pan and replace the filter and clean everything, I normally use 14 quarts for these cars. Old fluid does nothing but hurt the trans and interfere with the clutches applying, you also must do a relearn with the AA80 or it will be unhappy

 

This is the first time Ive heard of a relearn? I typically replace exactly what I change out.. I think I even have a writeup on here about it. Thanks for all of the replies.. What's the relearn ?

 

This trans self adapts fill speed, apply pressure, and timing for every gear to offset clutch wear and to adapt to driving style. If you just swap fluid none of these values will be correct for sheered down, old dirty fluid and it will shift oddly for a good while as it tries to figure out the new fluid.

The relearn prevents all this by informing the trans it needs to reset and figure out new adaptation values and it will begin from the assumption the fluid is new and it can use stock or very close to stock values. All you need to do it is drive it around following the instructions on the screen of your scan tool, you just accelerate up through all gears very very slowly for 2 runs, let the car glide down to near stopped each time, then drive it around normally for 2 runs, then do a few WOT pulls.

After that each gear should've been high and low pressure and fill speed adapted, you won't have any hesitations, mini-flares, confused shifts, banging from multi gear shifts etc. If a trans is doing poorly you can manually input offset values to force it to behave as well, I've never needed to do that though.

If you don't do a relearn it will have some weirdness, I tested this on my 07 when I serviced it the first time. It was shifting a little "odd" until I finished the process

 

What if you don't have a scan tool and is this the same for an LS 430?

 

If you don't have one then it will eventually learn but may act weird depending on how sheered down/old the fluid was. Hopefully without causing issues while it figures it out, I've never owned any car without a scan tool that can do anything in said though so I'm not sure. I current have techstream (most difficult to use and limited) and an Autel ultra for my Toyota/Lexus stuff. I also have VAGCOM but I normally just use the Autel anyway for the same reasons since the factory software just sucks for ease of use and capability

The A650E doesn't really need a relearn as it never really wears out, main issue with it is the control ECU not the trans itself.

Not sure about the 6 speed. It's been too long since I've done mine and I don't remember but I can see if that option exists

 

is there a procedure for this using techstream?

 

Probably, but I've never bothered looking. I've honestly never had good reason to use it yet as it's just not great in terms of ease of use and support etc. Very cludgy

I used to use it when I had my LS430 but I bought an Autel Elite 2 about 3 months into owing that car for use at my shop and once I tried it in my own car I never used techstream again.

 

awesome sauce