Did Ford Ruin their Manual Trans? - Engineering Explained

[Norm Peterson]

I agree 4.09's are absolutely worth while in general.

Have to say I can't see any benefit to being able to get easy wheelspin in 2nd gear as well as in 1st. Once you've made overall gearing in 2nd short enough to be useful as a 1st gear, what's the point of having a transmission gear even shorter (and less useful) than that?


Norm

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[spaz mk will]

Have to say I can't see any benefit to being able to get easy wheelspin in 2nd gear as well as in 1st. Once you've made overall gearing in 2nd short enough to be useful as a 1st gear, what's the point of having a transmission gear even shorter (and less useful) than that?


Norm

Even with the tradeoff of first gear, I think the idea is to make 2-4/5 more engaging and responsive in daily driving. Trying to best emulate the 15-17 experience with 3.73 which comes with more shifting and therefore involvement, if you define it that way. That’s all personal preference whether that sounds like a good time or not.

4.09 is on my “Maybe” list of mods, large effort to do it aside. I’m not sure I want it DD or if it would be good for autocross (probably makes 2nd too short or too powerful in many instances) but the idea of a more lively bottom end to the powerband and some more shifting is enticing. We’ll see.

 

[Norm Peterson]

Even with the tradeoff of first gear, I think the idea is to make 2-4/5 more engaging and responsive in daily driving. Trying to best emulate the 15-17 experience with 3.73 which comes with more shifting and therefore involvement, if you define it that way.

Why not just use more throttle instead?


Norm

 

[boB]

With the 3.73 gears each shift (1-2, 2-3, 3-4) at 7000 rpm drops the engine right into the fat part of the torque curve (about 4500 rpm) for the next gear. That seems just right for acceleration. Closer ratios may be nice for road racing but with probably far less than 1% of Mustangs doing that it is not worth developing a transmission for that. The serious racers can install a Hewland.

Maybe this has been posted before, I couldn't find it.

 

[Norm Peterson]

With the 3.73 gears each shift (1-2, 2-3, 3-4) at 7000 rpm drops the engine right into the fat part of the torque curve (about 4500 rpm) for the next gear. That seems just right for acceleration.

That's fine when you're chasing acceleration based on SOTP feel. But in normal street driving you're really more likely to be shifting at or below 4000 rpm. What does the gen 3 Coyote torque curve look like at/under 2700, and why should anybody feel the need to push on past 4500 just to avoid soft acceleration in the next gear? That's what gear spacing that's almost 1.5 to 1 gives you.

Closer ratios may be nice for road racing but with probably far less than 1% of Mustangs doing that it is not worth developing a transmission for that. The serious racers can install a Hewland.

That's going too far in the other direction. Like with a close-ratio Magnum XL where the top 4 gears are spaced no more than 1.30 to 1 apart.

Good gear spacing for a road car lies somewhere in between.


Norm

 

[boB]

What does the gen 3 Coyote torque curve look like at/under 2700, and why should anybody feel the need to push on past 4500 just to avoid soft acceleration in the next gear?

The 5.0 has about 375 lb*ft at 2700 rpm, more than enough for unsoft acceleration. Even at 2000 (where I often cruise) it has over 325.

That's going too far in the other direction. Like with a close-ratio Magnum XL where the top 4 gears are spaced no more than 1.30 to 1 apart.

Good gear spacing for a road car lies somewhere in between.

The Hewland suggestion was partly in jest although I was once shopping for one for a trackday toy. Road car gearing is a big compromise, maybe Calimer can put the '17 internals in a '18 case?

 

[shogun32]

maybe Calimer can put the '17 internals in a '18 case?

probably easier and more sensible to just drop a Mach1 TR3160 into place. The 'auto-blip' will be off but what kind of driver uses that?

 

[boB]

The 'auto-blip' will be off but what kind of driver uses that?

This driver does, it worked really well at Daytona.

 

[Norm Peterson]

The 5.0 has about 375 lb*ft at 2700 rpm, more than enough for unsoft acceleration. Even at 2000 (where I often cruise) it has over 325.

Fair enough.

Makes me wonder why 375 ft*lbs x 2.10 x 3.73 at the wheels isn't enough for some people. Yeah, there's probably a 12% or so efficiency loss, but 2600 ft*lbs at the tires ought to be enough to make wheelspin just from rolling into the throttle an iffy proposition. Even at the 325 ft*lb crank level, that's enough for nearly 0.5g forward acceleration (and that's in second gear).


Norm

 

[Dfeeds]

I can't find the post but I recall someone who got the 4.09 gears and actually lost time on their 1/4 mile because they had to make one more shift than before. For whatever that info is worth.

 

[ice445]

Fair enough.

Makes me wonder why 375 ft*lbs x 2.10 x 3.73 at the wheels isn't enough for some people. Yeah, there's probably a 12% or so efficiency loss, but 2600 ft*lbs at the tires ought to be enough to make wheelspin just from rolling into the throttle an iffy proposition. Even at the 325 ft*lb crank level, that's enough for nearly 0.5g forward acceleration (and that's in second gear).


Norm

Because compared to a large displacement Hemi or LS, it feels mild. Even though numerically it isn't.

 

[boB]

Fair enough.

Makes me wonder why 375 ft*lbs x 2.10 x 3.73 at the wheels isn't enough for some people. Yeah, there's probably a 12% or so efficiency loss, but 2600 ft*lbs at the tires ought to be enough to make wheelspin just from rolling into the throttle an iffy proposition. Even at the 325 ft*lb crank level, that's enough for nearly 0.5g forward acceleration (and that's in second gear).


Norm

Some calculations show a driveline loss of as much as 16% and then there is the power used just to accelerate the flywheel/clutch, maybe as much as 15 HP to go from 2000 rpm to 7000 in 1st gear. I'll have to do a test to get an estimate of acceleration in 2nd gear using the built-in recorders.

 

[Norm Peterson]

Some calculations show a driveline loss of as much as 16% and then there is the power used just to accelerate the flywheel/clutch, maybe as much as 15 HP to go from 2000 rpm to 7000 in 1st gear. I'll have to do a test to get an estimate of acceleration in 2nd gear using the built-in recorders.

I was assuming the use of a 1.00:1 transmission gear and hypoid gear efficiency in the middle of the range (neither horribly inefficient nor exceptionally efficient).

Indirect gears would show lower efficiencies due to the power having to be transmitted across more pairs of gears.

I'm fully aware of other parasitic losses. The math is easier when you work on a torque basis with rotational inertias and rotational accelerations that are consistent with forward acceleration of the car. It's a huge spreadsheet, though, about 13,000 KB by the time I added the ability to compare two separate cases. The basic acceleration simulation is something I've been tinkering with off and on since about 1968.


Norm

 

[Silver Bullitt]

Those torque numbers are pretty stout based on my stock numbers (pre and post res delete/h pipe).

 

[Norm Peterson]

Those torque numbers are pretty stout based on my stock numbers (pre and post res delete/h pipe).

So about a 10% efficiency loss based on Ford's 460 HP advertising.


Norm

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