Why a clutchless transmission?

[Hemi Joel]

At Bonneville Speed Week 2013, I saw that one of the faster cars dropped out when his clutchless manual trans failed. I don't remember if it was a Jerico, G-force, Liberty, or what. So, why a clutchless manual transmission on the salt? (pardon me that I know just enough to think of stupid questions) Is there an advantage to the lightning quick shifts when the track is 4 miles long? Is it a worthwhile trade off for the potential failure of the split slider springs that can't happen on a clutch assisted trans? I'm just curious.

Thanks, Joel

[JoeyG]

I would think it's the less chance for a clutch explosion from the extreme long duration/stress or maybe the effect of removing a possible power loss point from the drive-train by directly coupling the driveline.

[DanStokes]

I'm guessing here (200+ MPH has never been a "worry" of mine) but I'm guessing that the cars are push started anyway so the clutch simply isn't needed with the right trans. Less to fail. And Joey has a great point, too.

Dan

[Dynoroom]

There really is no good reason, at least for most LSR cars.

They are VERY expensive and complicated (the air shifters anyway). Most cars under 250 MPH probably are in high gear before the 2 mile marker (not so for the faster liners) so no shifting the last 3 miles.
They can be hard on the drive line shifting under full power.
And the biggest issue to me is if you lift off the throttle in any gear except high they will fall out of gear requiring you to shift to the next gear.

That being said lets take a look at some pluses....

The driver doesn't need to hunt for the next gear, with the pull of a handle or the push of a button you're in the next gear.
Time is a factor when shifting for the fast cars as they are moving 300 to 400 feet per second or more. The time it takes to "find" the next gear with a manual shifter and all the drivers gear we wear in land speed racing (3 layer suit, hans, arm restraints, etc) this can be a few seconds. 300 MPH = a 12 second mile, time is important.
And don't forget El Mirage or some of the mile tracks. At those places you can't afford to give up any time during the run, so a quick shit is important.

All the above being said, I run a Jerico air shifted 5 speed in my car and these are some of the things I've noticed. It did make it easier for me to teach my sons how to race the car because I didn't worry about clutch and shifting issues, just push this button when the shift light comes on.....

[YELLA BRICK]

And don't forget El Mirage or some of the mile tracks. At those places you can't afford to give up any time during the run, so a quick shit is important.

Sorry men, It's childish and immature, but I couldn't hep masef !

[Dynoroom]

I knew I had poor spelling but.......

That stinks!

[TheSilverBuick]

And thanks for the explanation Mike.

[DanStokes]

Mike has given you the REAL answer. Never mind the "elimination" comments.

Dan

[Barry Donovan]

an all or nothing throttle is for quick shifts, not so much about quick shifting.

some cars (my subaru drivetrain) has a scoop on the bottom of the bellhousing taking in air to cool the clutch area.. it would get pulverized, depending on materials (just road salt melts oem subaru clutches here)

other than that, I cannot think of any other reasons.

[Hemi Joel]

There really is no good reason, at least for most LSR cars. They are VERY expensive and complicated (the air shifters anyway). Most cars under 250 MPH probably are in high gear before the 2 mile marker (not so for the faster liners) so no shifting the last 3 miles. They can be hard on the drive line shifting under full power. And the biggest issue to me is if you lift off the throttle in any gear except high they will fall out of gear requiring you to shift to the next gear. That being said lets take a look at some pluses.... The driver doesn't need to hunt for the next gear, with the pull of a handle or the push of a button you're in the next gear. Time is a factor when shifting for the fast cars as they are moving 300 to 400 feet per second or more. The time it takes to "find" the next gear with a manual shifter and all the drivers gear we wear in land speed racing (3 layer suit, hans, arm restraints, etc) this can be a few seconds. 300 MPH = a 12 second mile, time is important. And don't forget El Mirage or some of the mile tracks. At those places you can't afford to give up any time during the run, so a quick shit is important. All the above being said, I run a Jerico air shifted 5 speed in my car and these are some of the things I've noticed. It did make it easier for me to teach my sons how to race the car because I didn't worry about clutch and shifting issues, just push this button when the shift light comes on.....

It is great to hear from somebody who has been there/ done that! Thanks for the answer, it makes a lot of sense now.

[greenjunk]

As a mile racer, I gotta go with strength. I've made a tko600 into a paper weight in under 3 miles. you just can't break a tex or a jericho or a g-force. They shift better then any synchro trans, and unlike the rest of the car its just a part i'm never worried about, at all.

[Monster]

We run a Jericho ...

[DanStokes]

Hi Steve! Hope all is well.

Dan

[Kix]

Just to clear this up a little... when most people talk about a "clutchless" transmission, they don't mean that there is no physical clutch between the engine and transmission.

The term "clutchless" usually refers to not using the clutch to shift between gears. A true clutchless trans uses a split slider that syncs with the upshift gear as it lets go of the previous gear, and this is done under full throttle. Thus, no clutch needed during the shift. The downside is that you have to hold the trans in gear unless you are under full throttle. Let off just a little and it pops into neutral. Another trans which people commonly refer to as "clutchless" is actually a "clutch assisted" trans.. which is still shifted without using the clutch... but you must lift slightly from full throttle and unload the trans for a micro second so the syncro can match speed and slip into the selected gear. This type of trans will stay in gear for decel and does not have to be held in with the shift lever.

The quick shifts are extremely important in drag racing (read: pro stock and a Liberty), nice to have in a mile, and really unimportant at Bonneville until you get way up on the aerodynamic wall at near top speed. We shift from 3 to 4 at 9,000 rpm and only lose about 650 rpm on the shift to keep up on the power band. If you get this wrong you will actually slow down when you shift into high gear. But down low, the speed of the shift doesn't mean much of anything. In fact, if the salt is loose in the first mile... a lot of guys use the clutch on the 1-2 and come back in soft, as you can blow right through the tires with a full throttle shift.

For the most part, Maty hit it on the nose... its mostly about strength. These transmissions typically use straight cut gears, as opposed to weaker bevel gears, which are cryogenically treated and micro polished. They are extremely strong and extremely efficient. A Jericho 5 speed has been known to handle almost 2,000hp in a 7,000lb vehicle at Bonneville... and lives.

Hope this helps!

Kix

[KeithTurk]

Honestly most of us use a Clutchless because it's the strongest technology that works, Nascar needs a Gear Driven transmission for it's top series, while they develop over the years the left overs filter down in racing and most of us can afford the used transmissions. Ultimately they are super strong and exceptionally reliable. So they work.

Like Mike Said...They shift quick which keep the suspension loaded and prevents unsettling the car at speed.

Right now it's the best, cheapest technology available... Soon as someone comes up with a better solution we'll jump on that.