The Stovebolt Site Forums The Shop Area General Truck Talk Double clutching

On Car Talk this morning a guy called in about his 1935 GMC pickup. He wanted to know how to double clutch.
I, personally, have never had to drive a vehicle that required double clutching, but I understand what the theory.
My question.
Is double clutching done by ear? (I know, you use your fingers!) Do you learn the sound of the engine compared to the speed of the vehicle?
Vehicles that require double clutching usually didn't come with tachometers.
If you can drive one vehicle "by ear" can you get into another one and drive without grinding?

My 38 chev requires double clutching. When it comes time to shift gears by listening to the engine RPM's put the clutch in take it out of gear let the clutch out. When your in neutral put the clutch back in before you put the truck into the next gear. I haven't mastered the art of downshifting yet without grinding it takes practice I guess

Mostly by ear with some feel. Right, you learn the sound that the engine should make (rpm) for any given MPH and gear combination.
Given the two constants of MPH and gear selection at the time of shifting you vary the engine RPM to match what you have practiced and remembered it should be for the situation.

If you can drive one by ear you can learn the sounds and feel of another quickly, but you will crash a few times as you learn each vehicle.

Grigg

Every vehicle I own except my Chrysler 3000 requires a double clutch to shift. The 3000 has the whacky auto stick.

Double clutching is as easy as pushing the clutch in once to put the transmission in neutral, letting out the clutch for a quick second and pushing in the clutch again to shift to the next gear.

Practice up shifting. It is easiest. You don't have to mess with the gas pedal if you don't want to and you can let it sit in neutral a little longer without screwing up.

The whole reason to do it is to get the gears spinning to help mesh them together when you finally do shift back into gear.

Down shifting is a little trickier but you are more than likely slowing down so you don't have to be as precise with matching the speed, or you can skip the whole process and use the brakes.

Shifting into 1st gear is darn near impossible, so don't try until the truck is at a complete stop. It will save the gears and your ears.

It does take a little practice to make it second nature, but hey you need a reason to drive your truck more anyway.

I learned how to double clutch on my Austin Healey and it id virtually the same on my truck.

Once you get that mastered lets start another thread on heal-tow shifting through corners.

Have fun.

I can heel-toe shift on my Road King.

Is heal-toe shifting not double clutching?

I often double clutch my newish VW while slowing down hard, in a turn or not. I use the left side of my right foot on the brake and the right side on the gas to match engine speeds before completing the shift and letting the clutch out.

It helps the synchronizers and also the clutch to last longer by matching speeds even with a synchronized transmission. You won't hear the gears grinding if you mess up, but you can watch the tachometer as you let out the clutch, it should stay steady as the clutch is released. If it jumps up or down then you did not have the engine speed right as the clutch was let out.

Grigg

I haven't gotten the bloody thing to downshift yet. I learned how to drive a stick on a newer car with syncros, so nobody taught me the Ancient Art of the Embrayage de Deux.

Grandpa -- the big showoff -- can do it in his sleep, even after all these years.

brendan just tap the gas when you let the clutch out in neutral that will bring the rpm up to complete the downshift

You really don't need to use the clutch at all except for starting, even with a crash box. Just shift to neutral, match RPM with speed and shift to the desired gear. I've driven an MG TD for a couple of weeks with a broken clutch rod and a bad battery (I was in the service and had to wait for payday). That involved starting it in neutral with a starting crank, pushing it to get it rolling, jumping in and jamming it in low shifting through the gears up and down and serious route planning to keep from making complete stops. I made alot of turns in parking lots and gas stations waitng for lights to change.

When you can double clutch & split shift a 2 speed axle at the same time then you know you are a truck driver.

kb3csw has it right, just tap the gas in neutral to keep the rpm's up.
tomo

I don't use the clutch on my 3100 much.It will just fall in to the proper place when every thing meshes up.Drove many big trucksback when you had 2 gear shifts 4x4 was my favorite.

Maybe the truck tranny is different but I don't have to double clutch my 38 coupe.

Baldy, I was lucky enough to have a battery and starter strong enough that I would leave it in low gear and hit the starter. It would "fire" and off I would go. In my early years I changed a lot of 55-56 cars to straight drives and I always had to do this to get to a welder so he could weld the clutch bracket on the side of the chassis for me. I use to do it "just for the fun of it" in my later years just to show off......

Achipmunk,

New vehicles have to many safety devices to be safe. Starters that won't spin unless the clutch is depressed now keep you from being able to do that and make it impossible to move the vehicle on the starter to get it off the road if it is disabled.

Tiny,

Truck fourspeeds were crash boxes in 38, three speeds had syncros.

In my old '51 Ford 1-1/2 ton with its crash-box,I got lazy;I'd just feather the throttle,pull it into neutral,stab the clutch and grab the next gear. For downshifting,same maneuver except give it a shot of throttle while hitting the clutch. No problem. drove my best friend crazy-he drove a OTR super-tanker,and couldn't drive my old beater across town without scratchin' gears.
Speed

you can shift without the clutch but it's better to learn to do it with the clutch first to establish the habit of timing and the ear for rpm. Once you get it down you really only need to tap the clutch enough to release the pressure as you shift as opposed to going to the floor.

Double cluthin,floatin the gears,no big deal.Just takes practice.Done it all in the big trucks.9 sp.,10,sp,13.,sp.18 sp.all of them.Right now I am driving a Freightliner with a 500 Detroit Series 60 and a 10 sp.Fuller.The only time I ever touch the clutch is to come to a comeplete stop and take off.

I was talking to a gentleman I know that has been a truck driver for the last 60 years. I was asking him about the "double-clutching" topic. He taught me to drive truck years ago and with some practice you always have it. Anyway, he was telling me that the toughest truck he ever drove was a '52 Ford F-7 firetruck with a Lincoln OHV motor and a 5 speed. He said that you could'nt shift that truck without using the clutch and double clutching it. He said no matter how much you tried you could never shift it up or down without the clutch.

Gentlemen:

It's not a matter of my not knowing the mechanics of the double clutch.

It's a matter of my not having had someone show me how it's done so that I have some sort of idea as to when to shove the transmission back into gear.

(I'd ask Grandpa, but he has his hands full with Grandma [and not in the fun way]. Dad will show me in the spring.)

good luck, practice will solve it, all of us have missed a few (some of us many). Just pity those who've never had the opportunity.

The key word is practice, practice, practice! Every one of these old girls is a little bit different. They all have their own personalities. The longer you drive yours, you'll get to know how it acts, and what its particular quirks are. Eventually, you'll be running through all the gears without a sound.

iv had trucks before i could shift with out useing the clutch you would have to get the rpm just right and it would slide right in and out of gear