2025 Hybrid Gear Ratios & HF45 Transaxle Technical Info

[The Real Maverick]

If would be nice if someone who owns a 2025 Hybrid and a scan tool could record these numbers also. This way we can see what has changed.

IF YOU OWN A 2025 PLEASE CONTRIBUTE TO THE POLL.

When engine is off, and you drive in "EV Mode" the Traction Motor does all the work, but the Generator spins in an equal but opposite direction. The Generator to Traction Motor gear ratio is 1 : 1. That was not always the case in earlier Ford hybrids.

The Traction Motor is geared directly to the output (differential). Therefore Motor Speed is always proportional to wheel speed, in any and all modes.

Chart with raw data. No data logger, so had to use photos. I shot video so have 100's of frames. Just a few frames posted here.

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[The Real Maverick]

Generator to Engine Fixed Gear Ratio

To rev the engine standing still, truck had to be in PARK. My limiter was set to about 2050 RPM. Idle is 1250 RPM. Traction motor is standing still so is out of the equation.

 

[The Real Maverick]

I suppose this makes sense in retrospect, since the gear size on the Generator and Traction Motor are the same; experimentally, the fixed gear ratio between engine and Traction Motor worked out to be the same. Now, to get the generator to stand still is a little tricky. But it occurs most often at about 55 mph and light load.
Note at 55 mph and light load it is impossible to generate, because it's not spinning. No problem. At "light load" you don't need it anyhow.

The above image is not a video.

 

[The Real Maverick]

At 60 MPH the truck goes 1 mile in 1 minute.

The tires are 729 revolution per mile. So they spin 729 RPM at 60 MPH.

The Traction Motor spins 7500 RPM at 60 MPH.

Ratio is 7500/729 = 10.29 : 1

 

[The Real Maverick]

Final Drive Ratio
Is that Engine to wheels?

60 MPH (+/-) indicated but imprecise.

Engine 2681 RPM
Generator 1898 but 3.54x gear ratio so subtract 536.

Engine net would otherwise be 2145.

2145/729 tire speed = 2.94 : 1

Experimentally close to the published 2.91 : 1

Another example:
Speed: 56 mph
Tires: 680 at 56 mph
Engine: 1952
Generator: 3 (appox. zero)

1952 / 680 = 2.87 : 1

 

[The Real Maverick]

Those with 2025's should be able to experimentally calculate like I did. Especially if your window sticker has a different drive ratio then you were expecting.

What else are you curious about?
Let me know.

 

[dochawk]

Final Drive Ratio
Is that Engine to wheels?

it generally means engine to driveshaft.

Most vehicles for the last century or so have a 1:1 final ratio, unless equipped with overdrive.

Then there's a 3 or 4 to one ratio to spin the driveshaft.

 

[The Real Maverick]

The much talked about "planetary" is quite a diminutive piece physically speaking.

HF45 - Enjoy!

 

[The Real Maverick]

Final Drive ratios

Gen 1 3.04 : 1. 2005-2008. Aisin HD-10
Gen 2 2.54 : 1. 2009-2012. Aisin HD-20
Gen 3 2.91 : 1. 2013-2021. Ford HF35
Gen 4 2.91 : 1. 2021-2024. Ford HF45
Gen 5 3.37 : 1. 2025- Ford HF55

In tear downs of the first four, they are visually identical to the observer. No visually apparent changes. I have not yet seen an HF55.

 

[MetalsGeek]

... to get the generator to stand still is a little tricky. But it occurs most often at about 55 mph and light load. Note at 55 mph and light load it is impossible to generate, because it's not spinning. No problem. At "light load" you don't need it anyhow.

Thanks for the good and useful data. It would be really interesting to know the current & voltage at each motor to reveal the direction of torque. Since engine & generator are coupled, if the generator has zero torque, the engine must as well, so running it under these conditions (low load 55) would be pointless and just waste fuel. It seems to me that the starter/generator has to have enough juice flowing to offset engine torque whenever the ICE is spinning. The implication here at "low load 55 with ICE running" is that the traction motor is now generating power to hold the starter rotor while the ICE is powering it all. It's quite fascinating to contemplate all the interactions under various conditions of speed and load.

 

[HeyBales]

Typical trip to work. Mainly highway up to 65.
(yes as you'll perhaps notice - I hit the Go pedal for some ICE warmup while I put on my seatbelt and get radio right and glance over neighborhood before I take off. I go up hills no matter how I leave, ICE is turning on soon no matter what.)
Prior to getting on highway, likely engine braking brought on down a hill, didn't review it to confirm if it happened this time.

Shows all three RPM's and Torque, and more. Easily see the spin direction of GM to TM.
Due to the update speed from different modules, and some readings are of course from different modules - a line won't always be a true match between different systems. Like 12V battery showing the Start Amp draw but a few lines later the DCDC High & Lo currents being brought online, when it really happens same time for a start.

Enjoy. I'm putting together a compile of 12V battery charging schemes from a lot of these.
From Forscan Lite on Android.

 

[The Real Maverick]

From Forscan Lite on Android.

I opened your file on a phone.

I did see that generator torque is almost always negative.

Negative means it is being pushed (driven). Positive means it is pushing (driving something else.)

Only positive torque was regen while ICE was on. When ICE is off, the traction motor does all the regen.
So up there above ~68% HV SOC you were getting a little engine brake effect. Maybe you noticed, maybe you didn't.

Your 12v and mine - both hover around 60%. But mine has been like that for 3 years now. Still stock. Still getting the job done.

 

[MetalsGeek]

Please do poll if you have 2025 Hybrid.

I'm disappointed your poll (and this thread) did not garner more attention.
I would love to know all the gear tooth counts, but overall ratios is almost as good.

 

[MakinDoForNow]

I'm disappointed your poll (and this thread) did not garner more attention.
I would love to know all the gear tooth counts, but overall ratios is almost as good.

As I understand in hybrid there is 1 tooth different between the 2.91 vs and the 3.+ Version. The torque is distributed by the planetary set and no gears are actually changed.

 

[The Real Maverick]

As I understand in hybrid there is 1 tooth different between the 2.91 vs and the 3.+ Version. The torque is distributed by the planetary set and no gears are actually changed.

Seems "improbable" that is the only change.
The advertised difference is about 15%.

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