double clutching

[Guest Packardsforever]

I've been reading about double clutching but have never done this or used it. One day I plan on getting a 25-32 senior Packard and want to know if I should use this technique and how to properly.

[bernardi]

I learned to drive on a Model A Ford. There were no synchronized gears, so double clutching was a habit. The idea is to get the various gears rotating so that they engage without "clashing". Later, the shift from first to second and second to third in most cars was synchronized. From neutral to first or neutrel to reverse was not. Shifting to either of those gears while the car was rolling was noisy.

So far as I know, double clutching is one of those things that never does harm, and in older cars definitely helps.

[Guest imported_Speedster]

Double-clutching is usually the only way I can get into 2nd gear, in my '29 Sedan, without grinding away gear teeth. Either that or just hold in the clutch longer, to allow time for the tranny gears to slow down, which is sometimes easier. That's the reason very High viscosity oil (680w) is needed in the tranny, to help slow down those gears when coasting.

[1935Packard]

If you've been reading about it, you've probable googled "double clutch" and seen a lot on the web. If not, check all that stuff out. The basic idea is clutch in, shift to neutral, clutch out, wait 1/2 second, clutch in, shift to new gear, give it some throttle, clutch out. It becomes pretty natural after a while.

[Matt Harwood]

Double clutching is exactly what it sounds like. Put the car in first, accelerate. When it's time to shift to second, put in the clutch, go to neutral, release the clutch, put it back in and pull to second, then release and continue accelerating. Do the same when shifting to third.

As said above, this better matches the speed of the gears inside the transmission to avoid crunching them. You can become quite adept at it with a little practice and it'll be second nature. In time, you may even be able to make the shifts without double clutching just by feeling the gears through the shifter. Long haul truckers without synchros on their rigs shift by feel and do it very well--even without the clutch most of the time!

Hope this helps.

[Rusty_OToole]

It's really a matter of matching engine speed to road speed.

When shifting up from 1st to 2nd let the engine speed die down until it is the same speed as the engine would be doing at that road speed in 2nd. In neutral. Then step on the clutch pedal and shift into 2nd.

When shifting down you need to rev the engine up to the same speed it will be in, in the lower gear.

Once you get the feel of this it is possible to shift without using the clutch at all.

I have driven around this way for something to do. But have also driven home with NO clutch after the clutch failed or jammed.

[Guest BigKev]

Or you could always do what a lot of old racers did and cut ever other gear tooth, so you can slam through all the gears without using the clutch.

Then again, probably not recommended for normal driving.

[Guest JT]

Bernardi, I also learned to drive on an A model at the age of 12. What a great time!

[mrpushbutton]

One thing I might add to the above informative comments is that you drive a car of this vintage differently than more modern standard shift cars you may have learned on.

With post-war cars you run the gear to the top of the torque curve of the engine then shift for each gear. With the older engines and transmissions the idea is to get from a dead stop in first to moving forward in high gear in a much shorter time frame, and shifting much earlier than you have in post-war cars. If you attempt to drive/shfit like a full syncro/large bore short stroke car (you know, Waaaaaaaaaaaaaaaa,waaaaaaaaaaa,wh-wh-wh waaaaaaaaaa) it's much harder to match up speeds if you attempt to drive it this way. Those old straight eights had a long stroke, and let the great torque of that long stroke take over and pull you up to cruising speed once you get it into high--soon!

[Rusty_OToole]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mrpushbutton</div><div class="ubbcode-body">One thing I might add to the above informative comments is that you drive a car of this vintage differently than more modern standard shift cars you may have learned on.

With post-war cars you run the gear to the top of the torque curve of the engine then shift for each gear. With the older engines and transmissions the idea is to get from a dead stop in first to moving forward in high gear in a much shorter time frame, and shifting much earlier than you have in post-war cars. If you attempt to drive/shfit like a full syncro/large bore short stroke car (you know, Waaaaaaaaaaaaaaaa,waaaaaaaaaaa,wh-wh-wh waaaaaaaaaa) it's much harder to match up speeds if you attempt to drive it this way. Those old straight eights had a long stroke, and let the great torque of that long stroke take over and pull you up to cruising speed once you get it into high--soon! </div></div>

That's true. Before automatic transmissions came in flexibility and a broad power band were prized. The true test of a quality engine was the ability to idle down to a walking pace in high gear then pull away without bucking or knocking all the way up to its top speed.

The preferred driving style was to shift into high as soon as possible and leave it there.

The long stroke, mildly tuned, low compression engines made driving this way sooooo easy.

[Guest ZondaC12]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BigKev54Clipper</div><div class="ubbcode-body">Or you could always do what a lot of old racers did and cut ever other gear tooth, so you can slam through all the gears without using the clutch.

Then again, probably not recommended for normal driving.</div></div>

HAHAHAHAHAHA this post honestly made me almost fall of my desk chair. I guess that WOULD work now wouldn't it? I cant imagine the noise that would emmante from the box though, and I have a feeling letting of the gas and getting back on would probably elicit a nice CLUNK too!

[Guest BigKev]

Jay Leno actually has a couple restored old race cars where this "gear tooth cutting" was done. He was explaining the process on an episode of My Classic Car.

[Clipper47]

In advertising the Electromatic clutch/overdrive Packard suggested that for driving around town the driver could operate the car without shifting by starting out in 2nd gear and then lifting the gas to go into 2nd overdrive. I must admit that it does work well but at the expense of using more gas. The torque and gearing of the 356" engine is such that starting in 3rd is possible without any lugging or hesitation but not something I routinely do. Moving over 4000 lbs.from dead stop in 3rd with an engine idling at 375RPM takes a lot of low end grunt even with a 4.09:1 diff.

[Rusty_OToole]

Alot of people used to start off in second then shift to high and leave it there. They only used low gear for starting on hills.

It worked OK and but was hard on clutches.

[Guest imported_PackardV8]

Jay Leno is confused. The gear TEETH are not cut off. The syncho teeth are cut off, everyother one.

If gear teeth are cut off then the gears will lock up. How would u cut everyother tooth from a gear with an ODD number of teeth???

[Guest imported_Speedster]

What you talkin' Bout here?

Doesn't 'Syncro-mesh' gears, also mean that there is an angle to the gear teeth, not perpendicular to direction of rotation, so they will engage easier?

I don't see how any teeth being removed would Work for very long, without causing damage to the remaining gear teeth ???

But the racers only needed it to last long enough to finish the race, didn't they.

[Guest ZondaC12]

I *think* having the teeth at an angle is called "helical gears" and "straight-cut" is what you would instantly think of when the basic idea of a gear comes to mind. Those give off that loud whining noise you hear when someone nails it in reverse.

The "synchro-mesh" is supposed to be just having synchronizer cones on each gear that causes the two that are going to be engaged to match speeds before the cogs try to engage, so they don't clash.

Someone please correct any mistakes I've made! I was very confused on this for a long time but from reading and talking thats the gist of it I would think!...

[Rusty_OToole]

Yes the helical gears are quieter than straight cut but more expensive to make and more friction. The friction is why they are unpopular in race cars.

The synchros act as a friction clutch to bring the gears to the same speed.

[Guest imported_Speedster]

Okay, so it Must be the gear Teeth that the racers were Removing.

[Guest imported_Speedster]

Hello Paul,

I like the Hat.

[Ozstatman]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BigKev54Clipper</div><div class="ubbcode-body">Or you could always do what a lot of old racers did and cut ever other gear tooth, so you can slam through all the gears without using the clutch.

Then again, probably not recommended for normal driving. </div></div>

Kev,

I'd think what you are saying is that they cut every second tooth on the engaging end so that the tooth tapered for a short distance before reverting to the full tooth width hence allowing the gears to engage easier. Please correct me if I'm wrong.

And my first car was also a Model A, so double clutching was a must for smooth driving, and you quickly became adept at it.

[Guest ZondaC12]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rusty_OToole</div><div class="ubbcode-body">Yes the helical gears are quieter than straight cut but more expensive to make and more friction. The friction is why they are unpopular in race cars.

</div></div>

Ah-HA!! I knew they were popular in race cars but had no idea why. Someone once told me they were more durable which would answer the question. But that sounds "more correct". Cool.

@ Speedster - thanks! I was bored a few Saturdays ago and decided to do a little time-traveling!!!

[Guest]

There is an alternative to shifting slowly or (as it should properly be called) double-declutching. You simply shift out of the gear you are in, into neutral and then by matching the relative speed of the gears, using the throttle to speed the input shaft up or let it slow down, simply slip the transmission into the next gear. Many truckers do this all the time. I have driven my daily driver since 1959 (386,000 miles) this way. However I don't do it any more. I missed a shift in November and made separate teeth and gears all over in my transmission. After a month to find parts and a few hundred dollars I now use the clutch, double-declutching when I am in a hurry, or just pausing in neutral when traffic is light.

[Guest BigKev]

Mal, yes that is what I am referring to.