10R80 Downshift Response Improvement

[engineermike]

Just another PSA...

I decided to work on the automatic downshifting of my Roush F150 and not only did I fix it, I uncovered some things along the way that some might find very interesting or useful.

The base drive downshifting was lethargic, slow to respond and usually made a couple of stops in gears on the way down to the final target gear. But I noticed that in Sport mode it would zap straight to the desired gear quickly and without making extra stops on the way down. Interestingly, copying the upshift, downshift, coastdown, pedal translation, torque converter schedules, etc. all from sport to base didn't fix the problem. It turns out there were 2 issues and I'll explain them separately:

1. The number of gears dropped per downshift: Apparently, Ford uses some insanely complex logic to determine how many gears to skip per downshift. It chooses the number of gears to drop as a function of weird stuff like road load, something called event lines, pedal position, pedal rate of change, drive mode, etc. and then looks up the ratios to drop in some sort of 4D matrix. There are something like 720 possible outcomes when downshifting from 10th gear. It's just nuts. The 4D matrix can be found in PCMTec by searching the navigator for "downshift event table". My understanding is that the outcome of all the calculations points it to a cell in these 144 tables. So, I copied the gear-specific column with the highest numbers to all columns for all tables for that gear (there are 16 per gear). This appears to allow it to skip straight to the gear you specify in the part-pedal downshift table.

2. The auto downshift delay: I logged these part-pedal downshifts in Sport and Base mode and found that upon tip-in, Sport mode would immediately (ok, milliseconds) send the signal to downshift. However, when doing the same thing in Base mode, it would delay 1-1.5 seconds. I searched and logged extensively to try to find this delay, to no avail. I did figure out another way to solve it, though. Table auF66752 basically takes the commanded drive mode and points it to a shift strategy. The column axis is the commanded drive mode, while the data in the table is the shift strategy it points at. 0 is base, 1 is sport, and they point to 0 and 1. Simple enough. This is the table that points drag mode to sand mode, for instance. Another example is in the F150, eco mode is pointed to the base shift strategy, which is why the F150 doesn't follow the eco shift schedules defined in hpt or pcmtec. Anyway, the simple answer here is to simply change base mode (0 column) to 1 (sport), and it then just defaults to the sport schedules and everything else shift related. I don't believe the pedal translation and stuff like burble mode follows; this table is just for shifting. The more complicated solution is what I did, where I pointed base mode (0 column) to sand mode (5) and then copied all my base schedules to sand. Now, I have my normal driving shift schedules when in base mode, but I get the very quick and responsive downshifts like sport does.

Between the above 2 changes, my truck now has millisecond-quick automatic downshifts right to the final target gear and it has transformed the driving experience. I wonder how many more people would love the 10R80 if it worked like this for all.

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[Weezox]

Not directly related to your two tables, but the theory behind it, I have noticed that there is a very clear difference between the transmission characteristics (especially in torque based shift scheduling) in "Normal Mode" but Shifter in S (not using paddles) and "Sport +" Mode with the shifter in D/S (doesn't change much). I don't know what on earth is causing this, I have looked at hundreds of these confusing tables in PCMTec and from everything I find it seems that "Sport (shifter) and "Sport +" (drive mode) should be both using the Sport mapping for all these tables as the car just sees the mode as "Sport".... I don't get it lol

 

[John S]

There are something like 720 possible outcomes when downshifting from 10th gear. It's just nuts.

Congratulations on exposing the complexity of managing the 10R80 calibration. This is partly why GM threw their hands up and went their separate way with their valve body design and calibration approach during 10R/10L development. The 10R80's target design/calibration priority was the 3.5 Ecoboost F-150 and Calibrators had to scramble resources to address the high revving Coyote applications and many transmissions were sacrificed trying to dial in a production-ready calibration for the 2018 Mustang launch. The sad reality is Ford gutted their Transmission Engineering group in 2022-2023 but Calibration Engineering still remains extremely challenging, as you've shared, to cover yearly vehicle and powertrain updates. With such limited ICE Powertrain Engineering staffing at GM and Ford, I feel sorry for the surviving engineers at both companies.

 

[V8Platty]

I would have to lose my left leg or right arm before I chose an auto trans in any car, but my 2020 V8 F150 did not have that option so I have been stuck with the truly miserable 10-speed auto.

You're probably right about the priority being given to the Ecoboost. If I drive in normal mode my poor V8 spends most of its non-highway time at roughly 1,000 RPM when going the local speed limits. Aside from lugging the engine, it also makes the truck feel like it has a hamster wheel powering it. There is simply no throttle response at such low RPMs and the damn thing never wants to shift down when it should. Clearly, whoever programmed the normal strategy for the V8 never actually test drove the truck! I understand maximum MPG is the goal, but at what cost?

So, I drive in Sport mode nearly 100% of the time and I live with the clunky hard shifts and high RPM holds because at least the truck is mostly in the right gear and drops gears quickly on throttle tip in when required. I'll give snow and rain mode due respect because it does actually do a good job in the snow. It may be a good transmission in theory, but in real life it just plain sucks.

Can that be cured with a tune? I suspect yes. Should I have to go to that length just to have it work properly? Absolutely not.

 

[Pistol_91]

Have you tried shortening the inertia duration? Or compared inertia duration base vs sport and the multipliers to see how much of a difference they are. This is probably where you can make it happen faster.

 

[engineermike]

Not directly related to your two tables, but the theory behind it, I have noticed that there is a very clear difference between the transmission characteristics (especially in torque based shift scheduling) in "Normal Mode" but Shifter in S (not using paddles) and "Sport +" Mode with the shifter in D/S (doesn't change much). I don't know what on earth is causing this, I have looked at hundreds of these confusing tables in PCMTec and from everything I find it seems that "Sport (shifter) and "Sport +" (drive mode) should be both using the Sport mapping for all these tables as the car just sees the mode as "Sport".... I don't get it lol

With PCMTec you can log MID93627 for drive mode selected, and MID 77885 the shift strategy. These are the input and output of table 66752 I mentioned earlier that selects which shift strategy to use with which drive mode. Maybe this will help shed some light on what you are observing.

 

[engineermike]

So, I drive in Sport mode nearly 100% of the time and I live with the clunky hard shifts and high RPM holds because at least the truck is mostly in the right gear and drops gears quickly on throttle tip in when required.

The high rpm holds is something called upshift backout delays. It's very easy to reduce or delete this "feature". It's also used for Sport in the mustang and Tow in the truck.

With table 66752 you can make it automatically use sport mode shifting without having to hit the button every time.

You mention clunky sport mode shifts, but I believe in the F150 it uses the same shift firmness (character) for sport and base. Only 4x4L uses a different firmness. Anyway, if you wanted to, you could make the shifts less harsh either by reducing shift torque or slowing down this shift duration a little. I can help guide you on all this stuff, as they aren't very difficult to do if you know what to do.

 

[engineermike]

Have you tried shortening the inertia duration? Or compared inertia duration base vs sport and the multipliers to see how much of a difference they are. This is probably where you can make it happen faster.

The inertia duration is on the other end of the shift as it's wrapping up. What I'm working through is on the front end, what gear it's commanding and when.

 

[V8Platty]

Engineermike, I understand what you are saying, but I am not sure I want to start messing around with transmission tuning in my daily driver! It's not great, but it is reliable.

As for the clunky shifting... In normal mode it feels like the clutch is being let out fairly smoothly. In sport mode, much of the time you hear a "kunk" when it shifts and it feels like it would if your foot slid off the clutch and it just sprung back up into place. Not a smooth shift in any way. Been like that since new. I just chalked it up to this 10-speed being hot garbage.

Amusingly, two different people told me they went to get a new F150 back when the 10-sp came out, and after test driving decided to instead buy a prior year pre-owned F150 with the 6-sp because they didn't like the 10-sp.

 

[John S]

I don't know much about 10R80 specifics but as transmission oil temperatures escalate, coefficient of friction of the clutch friction plates drops, reducing torque capacity of the clutch packs. Many transmission parameters are coordinated with the engine's ECU to truncate torque or manipulate the energy/inertia phase of a shift during gear changes (torque management is also backed into base calibrations,) so it's important to maintain proper communication between the engine and transmission when making changes to either calibration. I wish I had a better understanding of tackling the complexity of modern engine and transmission calibrations but keep up the good work, calibration engineers work full time, every day, trying to dial in the optimum calibrations for the masses while talented enthusiasts break into their "secret" world to make things even better. Keep up the good work and thanks for sharing.

 

[engineermike]

...Many transmission parameters are coordinated with the engine's ECU to truncate torque or manipulate the energy/inertia phase of a shift during gear changes (torque management is also backed into base calibrations,) so it's important to maintain proper communication between the engine and transmission when making changes to either calibration. ...

100%. I was trying to figure out how the clutch pressures were determined and logged them all. When I plotted clutch pressure vs engine brake torque and saw a linear relationship, the light came on. Someone did all the math to determine what pressure each clutch needs to sustain the calculated torque transferred by that clutch, reflected from input shaft torque. Realizing this made me realize how important the engine torque model is to transmission function. And all these companies selling tunes with hacked up torque models are lying to the transmission which will lead to transmission problems later.

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