- It seems like manufacturers today
just can't stop adding gears to cars.
Just a few years, we've gone from five or six speeds
being the standard to eight, nine,
even ten speed transmissions.
Honda and GM, they're working on gearboxes
that go up to 11 speed.
I want to know why do they keep adding more?
Well it turns out, there's a couple of good reasons
why you might want em.
And a couple of reasons why you wouldn't.
So today, we're gonna figure it out.
Let's go.
Truckers with their 18 speed transmission.
Pft. Ha ha.
Hold my beer, sonny.
Toot, toot!
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- I'm gonna get straight to the point.
One of the reasons why the number of gears in new cars
keep increasing is straightforward.
Fuel economy and performance.
But this can't go on forever
because extra gears creates some pretty big problems.
So to understand the benefits and drawbacks,
we need to see why cars have gears in the first place.
And that all starts with the sexiest part of every car,
the engine.
And especially its power curve.
I got a bunch of power curves, goes like this.
When I do this, that's the backside of my butt.
That's where I get all my power from.
These cheeks.
Slap, slap.
We often describe engines by their horsepower rating,
but that's only peak power.
Engines only make that at one particular engine speed.
And that's usually close to the maximum RPMs.
That's the rev limit or the red line.
So if you have an engine with a peak power output of
325 horsepowers and a red line of 6,000 RPM,
it's only making maximum power somewhere around
5,200 to 5,800 RPM, depending on an engine.
But this is a theoretical engine,
so let's just say it makes it at 5,800 RPM.
Now, before and after that point, it's producing less.
Sometimes a lot less.
At idle at around six to 800 RPM,
that might be making as little as 20 horsepower.
Mm.
Enough power for accessories like the alternator and
air conditioner, but not much else.
That's why if you want to try to accelerate at idle
without adding any throttle, your car creeps forward slowly,
and maybe will even stall out.
As engine speed increases, so does power output,
but as power output increases, so does fuel consumption
because you can't make power without it.
Now let's consider what would happen if your car didn't have
any gears at all.
That would be a direct drive system like a kid's tricycle.
Those have a one-to-one ratio between the drive system,
that'd be little Jerry's legs on the pedals,
and the driven wheel.
For every rotation of the pedals,
the wheel rotates one time.
So if your car had no gears, it would do the same thing.
For every full rotation of the engines crankshaft,
the wheels would rotate just one time.
And there are situations where that could work just fine.
In a car without gears,
at an engine speed of a thousand RPM,
the wheels would also be rotating at a thousand RPM.
Assuming your car has pretty typical tires,
say 25 inches in diameter,
you'd be traveling at 75 miles per hour.
So the one-to-one ratio of a direct drive
could be good for highway cruising,
but has a major low speed problem.
At five miles per hour,
your engine would be spinning at just 67 RPM.
Engines need to maintain a minimum speed
to have enough momentum to stay running.
That minimum varies based on things like the
weight and friction between internal parts,
but 67 RPM is too slow for anything you'd find in a car.
So you can solve that low speed problem by adding a
reduction gear to the car.
A reduction gear lets an input source, like the crankshaft,
rotate faster than the output.
The opposite is an overdrive gear,
which lets the input rotate slower than the output.
In that case, if we simply added a 15 to one reduction gear
then for every 15 rotations of the crank,
the wheels would just rotate once.
So at five miles per hour,
the engine would be spinning at a much happier 1000 RPM.
But a single gear solution to low speed problem
creates a high speed problem.
For the 15 to one ratio at 70 miles per hour,
the engine would need to spin at over 14,000 RPM.
Well past the rev limit for most cars.
Motorcycles, don't got to worry about that though.
Yeah, where my motorcycle boys at?
Yeah, yeah.
Leave a comment down below if you want more moto content.
Also hit that subscribe and like button.
That lets us know we're doing good.
Thank you.
With a 15 to one ratio, the engine will reach
6,000 RPM at just 30 miles per.
So you can see the problem here.
Any gear ratio that lets the engine accelerate
at low speeds, inevitably leads to problems at high speeds.
As vehicle speed increases, there is some point where the
engine speed goes beyond what it's capable of
and that's probably happened long before you've reached
highway speeds.
So what is the solution, Jer bear?
Tell me, I need the answer.
We add more gears.
The most basic reason your car has multiple gears is because
engines are limited by their idle speed and their rev limit.
Engine and wheel rotation speeds need to vary
if you want to travel at a normal range of vehicle speeds.
So transmission with a combination of reduction gears and
overdrive gears makes it possible for you to drive at
five miles an hour or 70 miles an hour.
Or if you're bad ass, 150 miles an hour.
Or if you're a super bad ass, 200 miles an hour.
As long as you're within the limits of the road.
Stay safe, my friends.
Even the earliest cars had more than
one gear ratio available.
The model T was a two speed and
two speed transmissions were common up until the 1970s.
But long before then companies started adding gears.
The 1927 Model A, three speeds.
And a three speed transmission stuck around
for almost 80 years up until the early two thousands.
In drag racing, three speeds are still common and
those are capable of exceeding 150 miles per.
So adding more gears isn't necessarily just about top speed,
but the addition of extra gears
does have a lot to do with performance.
And in the two thousands, six speeds became common in
performance cars.
It's really only in the last decade or so that we've seen a
widespread addition of gears.
So are six gear ratios not enough?
Well looking at a specific example
might explain why it might not be.
Like many cars, the Catfish Camaro built from 1998 to 2002,
had a transmission that wasn't built by the manufacturer.
It has a Borg-Warner T56.
If you know, you know.
Which was also used in the Dodge Viper,
used in Corvettes, Mustang Cobras, a lot of sick cars,
but on top of that list is the old Catfish Camero.
Now in the Camaro, the six gear has a ratio of 0.5 to one.
That's an overdrive gear.
So it multiplies the rotations of the input source
and that lets me cruise in the Camaro at a comfortable and
fuel sipping 1300 RPM at 60 miles per.
At that speed, it's 25 inch tires are rotating at 800 RPM.
Now you mathletes out there might be thinking
your boy doesn't know what he's talking about.
Shouldn't an engine spinning at 1300 RPM
with an overdrive gear ratio mean the wheels are
rotating faster than the crank?
Well, the answer is no.
I could tell you why,
but I think you should tell me instead.
Head on over to the Donut Underground Discord
tonight, 7:00 PM, and you can explain why the
Camaro's engine is spinning at 1300 RPM at 60 miles per.
7:00 PM.
I'll be on for one whole long hour. Okay?
I'll take your answers.
Whoever gets it I'll give you a shirt.
Be ready.
Now let's suppose that Nolan pulls up and
he wants to race because, let's face it, he's trouble.
I got a Mustang eater though,
that's the definition of what a Camaro is.
I'm not worried.
And because we're professional drivers on a closed course,
don't try this at home.
We go for it.
At 1300 RPM, the Camaro is only making 40 or 50 horsepower.
So I grab second. A-pow-pow.
A reduction gear with the ratio of 1.78 to one.
The engine jumps to 4,600 RPM.
Horsepower gallops up to 300, just shy of the engine's peak.
And I can accelerate all the way to 5,600 RPM
before the power starts to drop off before red line.
I win, take the cash, and the respect that I deserve
because my Camaro just gobbled up a little pony.
That's what I eat everyday.
I eat ponies.
Breakfast, lunch, dinner.
I got a sticker on the back of my car that says
My Little Pony eater.
Put it on a shirt.
But let's rewind the tape a little and see what happens
if I'm going 70 miles per hour instead of 60.
In sixth gear at 70 miles per hour,
with that 0.5 to one ratio,
the Camaro's engine is spinning at 1500 RPM.
That increased engine speed means it's using
a little bit more fuel.
And that's one reason why manufacturers will add more gears.
A seventh gear would be a ratio of 0.33 to one
and would drop the engine speed to just a thousand RPM.
That's a 30% decrease in engine speed and
that produces a corresponding, but not identical,
decrease in fuel consumption.
So, more gears means more time can be spent at lower RPMs
burning less fuel.
But more gears can also mean better access to
engines peak power.
Consider that race again.
This time starting at 70 miles per hour.
If I downshift into second,
the engine is going to jump up to 5,400 RPM
where it's already making maximum power,
but I'll need to immediately upshift to avoid over revving.
That shift takes time, slowing the car down,
maybe enough that Nolan gets an advantage and a win.
But your boy won't let that happen.
So what if I downshift into third instead?
Well, that's got a ratio of 1.3 to one and at 70 miles per,
the engine will only be at 3,900 RPM.
That'll put power at just 250 horses,
well below the engine's 325 horsepower peak,
a deficit that could also lose the race.
So could more gears help this problem?
Heck yeah it could!
So suppose there was a second and a half year
with a ratio of 1.55 to one.
70 miles per hour, that would put the engine at 4,700 RPM
or at about 300 horsepower
and with plenty of room to rev before red line.
So it sounds like changing from a six speed
to an eight speed in the old Catfish would be a win-win.
Better fuel economy and more performance.
But it's never that simple.
Never that simple.
Adding gears also has some downsides.
Some of the problems are pretty obvious.
Adding more gears means more parts in greater complexity
inside the gearbox.
Unless all those parts were made smaller,
that means increased size and weight.
And if they are made smaller,
then they potentially are more fragile and
can't handle the same amount of power.
Of course you could solve that by using stronger materials,
but that increase costs.
Freaking everything cool is expensive.
One problem that's not as obvious is that extra gears create
additional drive-line power losses.
That's power which doesn't make it to the wheels
because it's used rotating the mass of the drive train.
Stuff like the flywheel drive shaft in your axle.
Any gears that aren't currently engaged
are still spinning around and that makes them dead weight,
which takes power from the engine.
And finally, there's the problem of shifting
through all those gears.
It takes time to move from one gear to the next.
During those shifts, the car is actually decelerating
because there's no power going to the wheels.
So the performance benefit of having extra gears
to keep the engine and just that right spot
in it's rev range could be canceled out.
Either by the extra rotating mass of those gears
or if you simply have to spend too much time
shifting through them.
But your boy's a fast shifter, boy.
In theory, if you had enough gears and never had to shift,
you could always be in the sweet spot for maximum power or
for maximum fuel economy.
And that's really the goal of a CVT transmission.
But in the real world, those have their own set of problems.
While they have infinite variation gear ratios,
that comes at a cost of producing a lot of heat and
being limited to how much power they can handle.
Also people say they feel weird.
Been there.
Engineers have to make choices
no matter what the transmission type.
Typically needed to strike a balance between
performance and fuel economy with
just a few gear ratios to work with.
In manual transmission cars,
that's been six for a long time
with just a few seven speeds in recent years.
But then sometimes miraculous things happen.
The ZF8HP automatic transmission.
It's the one that started it all.
I'm a little bit old fashioned, okay?
I like my coffee black and I like my Pert Plus
to burn my eyes.
I also like three speed manual transmission.
You think people know Pert Plus used to burn your eyes?
- [Cameraman] I don't know what that is.
(laughing)
- But making one of those transmissions
with more than six gears
is susceptible to all the problems I just mentioned.
Size, rotating mass and shift speed especially.
Automatics on the other hand,
they can be engineered with really clever workarounds.
Because they can make more speeds, more gear ratios,
with fewer actual gears.
By doing that, the 8HP transmission
built by German company ZF, really launched the more speeds
with fewer gears trend all the way back in 2008.
And the ZF8 has been used in a huge number of cars.
Everything from relatively ordinary Dodge Chargers and
BMW sedans to the Lamborghini Urus and Aston Martin DBS.
So what makes this gearbox so special?
Like many automatic transmissions, it uses planetary gears.
We're going around the world.
Those consists of a sun gear surrounded by planet gears and
an outer ring gear.
The ZF has just four of these planetary gear sets,
but by mixing and matching the sun and ring gears,
reusing them to make different ratios,
the ZF manages to make eight total ratios
with just four gear sets.
Fewer gear sets means fewer gears sitting around
doing nothing so less rotational mass.
It also means fewer parts that can break,
decrease total size and mass and the gears don't have to
move as far to complete gear changes.
Fewer parts also means it's cheaper.
You have less stuff.
Old school automatics with ordinary gears had to shift
sequentially through each of their gears,
but the ZF design lets it jump straight between
certain gears, from eighth to second, for example.
And because all of this is computer controlled,
shifts happen in just 200 milliseconds.
Far faster than a human.
I don't know that's pretty fast.
I just went through six gears right there.
Nailed it.
The ZF8 has been installed in over
three and a half million cars.
Proving that transmissions with lots of gears can work.
ZF followed suit with a nine speed.
Ford and GM, they joined forces.
Me and Nolan, one, Camaro Mustang.
It'll never happen. It did happen.
And they built a 10 speed transmission together.
And now Honda and GM are working on an 11 speed.
GM didn't like working with Ford they're like,
forget you, man.
We're gonna go work with the Honda guy.
And Ford was like, you friggin loved it.
You loved it and you're leaving and it's your loss.
Your loss, baby.
But all of those are being built for mass production and
plan to be sold in the millions.
What if money was no object?
Fuel economy didn't matter?
And performance was your only goal.
Well, then you could do something really special
like what Koeninsegg has done with their Lightspeed.
A nine speed, seven clutch transmission.
Like the ZF, Koeningsegg uses a few gear sets,
six in total, in combination with each other
to create nine different ratios.
And because each gear set has its own clutch,
the Lightspeed transmission can jump from any gear
to any other gear, almost instantaneously.
It just takes two milliseconds to complete a gear change.
Finally, because it's not based on an
automatic transmission with a
liquid filled torque converter,
power delivery to the wheels is near instantaneous as well.
It's an engineering marvel.
If you want, maybe we should do a whole episode
on how it works.
Let us know in the comments.
But with plans to build just a hundred and twenty-five cars
and at a price of $3 million,
don't expect that technology to trickle down
to the rest of us anytime soon.
So is the adding of gears ever going to stop?
11 might not be the transmission's final form,
but there are two reasons why you won't see manufacturers,
apart from maybe Koeningsegg, adding gears forever.
First, there's a point where that adding efficiency
from a design, like ZF8's, with its fewer components and
factor shift, it'll peak.
Like you in high school.
Now when that happens, adding just one more gear
will start to make things less efficient and slower
just like it did with older transmission designs.
But the biggest issue is the electric future.
Because they don't have power curves,
EVs simply don't need as many gear ratios
as internal combustion engines.
Teslas get it done with just a single speed.
Run line instead of the engine's ability to deliver power
from zero RPM to as much as 20,000 RPM.
As internal combustion goes away,
gearboxes with almost a dozen ratios simply become obsolete.
You know, whenever we talk about internal combustions
leaving us, we never think about the transmissions either.
And I just want to say
I'm gonna miss the transmissions as well.
Because they were important, too.
You don't know what you've got until it's gone.
Okay, that was enough of that.
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Which is a genius idea that I came up with
in literally three seconds.
So head on over to donutmedia.com and
pick up your perfect stocking stuffer today.
- Thank you guys so much for watching this episode of B2B.
If you want to see us break down a particular transmission,
like the one that Koeningsegg has,
let us know, I'd be really,
I'd be really interested in nerding out
if you guys like these types of videos.
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