Changing ATF's and Shifting Behavior

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I am in the process of changing my old fully synthetic multi-vehicle ATF to the specific fluid my cars call for. Either DEX III, Toyota T-IV or Toyota WS. So far I have gotten to approx 90% of the vehicle specific ATF in the 4Runner and the LS400. In other words, the 4Runner has approx 90% Toyota brand Dexron III (3 drain an refills of 5.5 qts) and the LS400 has approx 90% T-IV (5 drain and refills of 3.5 qts). I drive the same roads everyday. I don't know if some of what I say is good or bad. Here are my observations. One is without question and the other does have some subjectivity to it. First, when I leave my house first thing in the morning in my LS400, I merely coast down the hill from my house. For the last 24 years the Tranny would stay in a lower gear until I got 2/3 of the way down the hill before it would shift up into a higher gear. Note I am just coasting, no throttle what so ever. The engine would rev higher as it coasted staying in a lower gear until about 2/3 way down when it would shift up and engine RPM's would go down. After changing to the T-IV it no longer does that. It goes to a higher gear almost immediately as I go down the hill. This is very interesting. Second, when I drive my 4Runner the 30 trip to work up and down the hills I observe it shifts sooner into a lower gear as I climb the hills. Before with the fully synthetic mulit-vehicle ATF the transmission would stay in the higher gear longer and was more apt make a dramatic downshift when it shifted. Almost like it dropped down 2 gears or it just stayed in the high gear a lot longer before it shifted down. I haven't changed the ATF in the newer cars in my fleet yet. Remember, both the 4Runner and LS400 have a bunch of miles on them. I have no credentials in mechanics and am making an observation that you all can say I'm crazy or and idiot or merely mentally incompetent. It appears with the multi-vehicle fully synthetic ATF I have been using for years worked fine in my cars. Look at the miles on my older stuff. Obviously my transmissions have been taken care of as I always change the fluid. I even have the scan gauge to check the ATF temp in my new stuff to make sure the levels are correct. Here is what I think. I believe the ATF I was using "hung on" longer than the OEM Toyota fluid. It didn't shift as often as the OEM does. Going down the hill in front of my house it "hung on" in a lower gear longer before it shifted. Going up hills it "hung on" longer than the OEM does. It appears it reduced the shifts. Now that probably is a good thing???? But from my point of view, the OEM produces a more smooth driving experience (At least on the 2 older vehicles) As I get to LS430 and GX 470 I'll update you. It may be a few weeks as I am going through some ATF. thumbsup
 

JC1

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I'm no expert, but I'm guessing the cleaner fluid is flowing more easily through the tranny and that is why it's shifting gears faster than you were previously experiencing. Did you change the filer/strainer as well when you did the servicing?
 
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Originally Posted by JC1
I'm no expert, but I'm guessing the cleaner fluid is flowing more easily through the tranny and that is why it's shifting gears faster than you were previously experiencing.
I'm also no expert, but I agree.
 

Gebo

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I didn't change filter. Didn't disconnect the battery. I've done drain and fills on LS400 every 10k. I've done drain and fills on 4Runner every 20k. I get about 1/4 out of LS400 and 1/2 out of 4Runner every drain and refill. I purchased LS400 with 30k and 4Runner with 85K. I've had them both a very long time. Trying to get entire recycle done every 40K.
 
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Originally Posted by Gebo
In other words, the 4Runner has approx 90% Toyota brand Dexron III (3 drain an refills of 5.5 qts) and the LS400 has approx 90% T-IV (5 drain and refills of 3.5 qts).
Mathematically you have 90% "new" fluid but in all reality, it's 100% unknown what the true mixture is. I can't explain the changes you feel though. From your first post, it sounded like you did it 3x (in a row) on one car and 5x (in a row) on the other car but your later post says these are done every 10k or 20k miles. That reiterates my comment about the fluid make-up being purely mathematical.
 

Gebo

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My normal fluid changes (drain and fills) were every 10k and 20k on these 2 vehicles. As I changed out the multi vehicle ATF and switched to Toyota OEM ATFs with drain and fills, I changed 4Runner 3 times in 3 days and the LS400 5 times in 5 days. I waited overnight for the ATF to be cold and measured it each time and replaced with the exact amount I drained out.
 

MolaKule

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Any new ATF will be cleaning the varnish off the hydraulic control valves and actuators. I seriously doubt the OEM fluid has anything to do with the programming of the hydraulic control valves and actuators
 
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Originally Posted by MolaKule
Any new ATF will be cleaning the varnish off the hydraulic control valves and actuators. I seriously doubt the OEM fluid has anything to do with the programming of the hydraulic control valves and actuators
I agree.
 
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Originally Posted by demarpaint
Originally Posted by MolaKule
Any new ATF will be cleaning the varnish off the hydraulic control valves and actuators. I seriously doubt the OEM fluid has anything to do with the programming of the hydraulic control valves and actuators
I agree.
Make that three. Adding, confirmation bias most likely explanation.
 
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Could the synthetic multi-vehicle atf have been too slippery? If the factory fluid provided more friction might it transfer more energy between the engine and wheels?
 

Gebo

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I finished my son's 2006 Highlander and we can't tell any difference after replacing the ATF. I'm wondering if it's related to the miles on the transmissions? I'm working on my LS430 now. Still got 4 more drain and fills to do (4 more days) on it before I can check it out.
 
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Originally Posted by irad
Could the synthetic multi-vehicle atf have been too slippery? If the factory fluid provided more friction might it transfer more energy between the engine and wheels?
No. If the fluid was the correct specification for the vehicle then the friction coefficient of the fluid is established by the spec regardless of the base oil composition.
 

Gebo

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Originally Posted by irad
Could the synthetic multi-vehicle atf have been too slippery? If the factory fluid provided more friction might it transfer more energy between the engine and wheels?
I would say, which I can't prove, is that in the oldest of my cars (20 years old) with the most miles that the multi vehicle ATF was too grippy. I don't know how to describe it but it seems the ATF held it in a gear longer. I make no claim to know how an AT works. From the above comments it appears the type of ATF makes no difference in how (when) it shifts as this is controlled by modules and electronics in the transmission. Maybe it just cleaned off the electronic doodads and such? That does cause me to wonder how they would be "dirty" with the religious frequency of my drain and fills??? Especially since I have lived in the same house for over 24 years and have had my LS400 since 2001 and it has always acted like I described earlier when I first cranked it up and was coasting down the hill in front of my house. Maybe the old fluid was a little more viscous when cold??? As a reminder, it only did this first trip down the hill in the morning. It wouldn't do it later in the evening. I know I can deceive myself and that is the worst type of deception. I could imagine smoother shifting. I know that. I know who I am. But I cannot imagine how the LS400 now shifts going down the hill. Before, I would have to "mash" the accelerator to make it upshift and leave that lower gear. I wondered what my neighbors used to think with me riding by their house with my "jake brake" on. LOL
 
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Originally Posted by KrisZ
Did you disconnect the battery anytime during or before the change? To me it sounds like the shift logic got reset.
You assume these cars have a shift logic transmission.
 
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