The Third Gen Tacoma Automatic transmission, why you hate it, and how we are reshaping it.
The 3rd Gen Tacoma has some funky stuff going on with it's transmission. We all know it. But why is this happening, and why do we hate it so much? Is it because it has two over-drive gears? We think not. While 2 overdrive gears are definitely part of the problem, it's not the primary problem, and there is a way around it.
We think it's the new logic (brain) behind the transmission that has too much freedom.
What do we mean? Lets explain below.
How does the new Aisin AC60F 6-spd automatic really work? The transmission itself (hardware) it setup quite similar to any other transmission on the market. There is not a magical recipe of hardware under the casing that makes this transmission act so badly. It's purely electronic.
So how does the electronics interfere with the operation of the transmission? Well, the operation is quite complex, and quite a new concept to Toyotas programming, and transmission programming in general.
Here is what we know and have tested.. and it may boggle your mind. The truck does not have determined up-shift and down-shift tables in the electronics. What? That does not make sense!
Actually, the way Toyota has it setup, it makes perfect sense. The truck does not have tables specific to shifting the transmission up or down. It only has tables that control shifting, in any direction!.
How Toyotas Transmission logic worked BEFORE the 3rd Gen Tacoma... Lets briefly explain how Toyota controls their transmissions, or how they used to, and how it helps you understand why you hate the 3rd gen transmission. Previously, Toyota had a way of controlling the transmission in their vehicles which makes complete sense and actually makes the transmission shift.. like it should.
Lets take the 2nd Gen Tacoma for example.
The 2nd Gen Tacoma used a series of tables that control shifting up to the next gear (ONLY UP) and a set of tables that control shifting down (ONLY DOWN). It then pairs these tables to a single (or double) transmission "torque" map that helps to create smooth shifts by pairing the shift to the torque of the engine.
Here is a brief diagram of this (simple example), and an explanation.
There are tables that control the limit (axle speed) of shifting the transmission up from one gear to the next, or shifting the transmission down from a higher gear to a lower gear. It will use the torque map to finalize the calculation of the shift and shift the transmission (as smoothly or forcefully as required, by the torque value).
This creates a very straight forward way of controlling the transmission, and is the reason it is so predictable.
The transmission can go up, or down. That's it.
Now how does the 3rd Gen transmission work? Absolutely nothing like this. Nothing like any transmission mapping that we have ever seen, and it is not like any of Toyotas previous transmission control code.
Lets start with How the transmission shifts. You would expect this to be straight forward, like the 2nd gen. However how the transmission selects a gear is controlled by an extremely complex algorithm. Not only is this Algorithm complex, but it has a certain degree of executive privilege that allows it to control the transmission far beyond what or how the driver would expect.
Now back to this sentence "The truck does not have determined up-shift and down-shift tables in the electronics."
Here is what we mean, with orders of diagrams in increasing complexity and explanations.
First, the gear control itself. There are similar gear based limits like the 2nd Gen Tacoma transmission. If all conditions are met, shift the transmission, (for example if you floor it, or you're near the rev limiter, etc).
This concept of shifting remains.
However, how does the transmission control which gear to go to? Good question.
The transmission uses what we would like to call "executive privilege" which controls what gear it will select. What does this mean. Take a look at the 2nd Gen Tacoma table again. See that there is a table dedicated to controlling the transmission UP, and DOWN?
Well the 3rd Gen Tacoma uses a single / primary table that controls ONLY the limits of the gear itself. It does NOT have control over going up or down, but rather only has control over the limits / conditions of when the gear can be used. What that means if all conditions are met, the ecu can select ANY gear, at ANY time that is required, as long as that gear meets the required conditions.
So there is no standard up and down blueprint here. There are simply 6 gears and that are accessible, at any time required, that the truck will use. If it wants 6th it will select 6th. if it "wants" 3rd it will select 3rd.
It does not "up-shift" from 2nd to 3rd. Rather it selects the gear. By modifying the code you can actually make the transmission "select" 5th gear after 2nd. Or "select" 3rd gear after 5th!.. Because the code does not go up and down. It selects in any direction as long as the conditions and thresholds are met.
It's a complex method of transmission control but this is only scratching the surface. It gets much more complex, as we continue on.
here is a simple diagram that may help you understand this gear control:
2ND GEN TACOMA STANDARD TRANSMISSION CONTROL
Here is the 2nd gen. you can go up in gears depending on conditions, or the transmission can go down in gears, depending on conditions.
REMEMBER THIS IS THE 2ND GEN TACOMA.
Now here is the 3rd Gen Tacomas control for gear selection:
Or, a super simple version:
The ECU will select whichever gear it desires. Independent of what gear it is currently in.
Note, for each gear there are 22 sets of tables that control limits. (depending on truck configuration some may not be used).
Now this is only the beginning of how shifts are actually controlled. Lets explain what modifies shifting even further. The torque calculation tables. Like the 2nd gen in the image above. These modify how and when the transmission will select a shift.
Now here is how the 3rd Gen Tacoma Transmission shifting actually works. It is simply put, insane.
Please understand this is actually quite difficult to create in a diagram, so this is a "close" match to what is actually going on. There is simply too many tables to put all of them on here.
Here is the takeaway from all of this information :
- The transmission does not, and will not shift in a predetermined manner of going up and down the way anyone currently thinks a transmission does.
If you "expect" the transmission will go from 5th to 4th, you're incorrect.
If you "expect" the transmission will go from 5th to 6th, again you're incorrect.
Any gear, at any time, is selected based upon the variables, limits, and calculations of torque / accelerator angle etc.
From that point the ECU will select WHATEVER gear it determines is necessary to match driver demand (gas pedal).
So, as you can see the ECU does not select gears and shift it like a traditional transmission would. Rather it selects gears based on various predetermined gear limits, torque calculations, and variables from the engine which help to select through the shift routine and actually create a "shift" event.
Note** this does not take into account ALL of the shift tables or torque tables. There are simply too many to show on a single graph. This does not take into account compensations or multiplications from the various 4D executive tables within the ECU.
So as you can see the ECU has a lot of executive privilege to shift in any direction or select any gear that it wants. Once again, this does not even take int account when you change the shift mode (ECT, S, etc).
So now that we can see this mess, what can be done? We are working on that!
Our new tune version dubbed "1.05" will release soon that completely rewrites the control of the transmission.
For example, we have managed to create a gear locking routine when you enable ECT mode and move the shift selector to S. Effectively doing what everyone has asked for S mode to be, a "true" manual mode.
No longer will the ECU automatically drop a gear or two when you floor it, in any gear.
This only scratches the surface of what we are changing in 1.05. We are completely re-tuning and changing the shift routines, the shift limits and torque tables. Eliminating the multiple redundant tables and effectively stopping the "learning" that everyone keeps mentioning about this transmission. We have confirmed already we can make the ECU follow only a single set of tables to select and determine which gear to shift to. This makes the transmission act much more closely to a normal transmission and shift the way we would expect it to.
We are also completely eliminating the need for multiple torque calculation maps that directly affect how and when the transmission shifts. This is one of the main reasons that the transmission is so unpredictable. We have, in the past tuned the 1-6 gear limit tables to be identical to each-other, expecting that the transmission may act more like we expect. However, over time the ECU will use different routines which in the end make the transmission shift unexpectedly once again.
Finally, we are modifying the 4D control / compensation tables and the multiple throttle tables, torque converter locking control / unlocking control tables to enhance shifting and transmission control even further.
It has taken us some time to understand the complexity of the new 3rd Gen Tacoma transmission to this depth, and we are very excited to show everyone what we can make it do with our 1.05 tune release. We are very confident when we say it may finally act and shift like a truck should!
Some of what we are working on fixing and improving in our 1.05 version tune, and the changes vs 1.04.
Toyota has released several TSBs to correct issues within the ECU. The latest version of the TSB has been voted the "best" yet some issues remain.
- Our 1.05 version tune will incorporate all of the current and previous TSBs into a single ECU file. This ensures your ECU is up to date, even if you don't have the latest TSB. (excluding ECU versions 04B00 and 04B01 which REQUIRE the TSB).
- 1.05 completely rewrites the shift logic on the 6AT transmission. Unlike 1.04, which only improves the shift logic, 1.05 completely rewrites the shift logic, and how shifts are determined.
- 1.05 eliminates the need for excessive redundant maps that alter how the transmission shifts.
- 1.05 update further improves our ignition calibration for these trucks. Enhancing ignition timing and ignition control over our 1.04 tune.
- Fueling is improved for both cruise and high load situations.
- ACIS valve control which contributes to the 3500 RPM "surge" in power is tuned to operate differently.
1.05 is a free update for all of our customers who have our tune kit. If you are interested you can order here, and update for free upon release.
**note information provided has been researched and tested via various means of controlling the tables / logic / programming of the transmission / reverse engineering and or other methods. Some or all of the information may be updated to be more correct upon finding new information, there may be critical components of the logic and programming that is not explained here, as this is meant as a simple representation of the complexity of the new transmission**