Question:
Was just wondering. In trucking school, your taught to double clutch. Is there any reason to double clutch? It just seems like it would be nothing more than a waste of time. Just wanting to get info
When you make fun of newbies, think back to when that newbie was you.

Answer:
Try clutching once like you do in a car. You'll get tired of grinding gears. Truck transmisions are not syncronized.

Answer:
Hmmm ... I was taught to keep the RPM's up, thus minimizing the use of the clutch!

Answer:
you can't shift a truck just pushing in the clutch
it ain't like a car where you can push in the clutch and put the transmission in any gear you want
you can double clutch,single clutch,not use the clutch and there ain't no way your going to get the transmission in 10th gear going 10mph,a car will go into 5th gear at any speed and just stall if you going to slow for that gear.
shifting a truck is hard,thus a skill is needed to drive a truck
you need to match engine speed to road speed for the gears to go togetter,if one gears is spinning faster than the other one inside the transmission they grind.
the truck I'v been driving lately 65mph is 1600 rpms,so if your doing 65mph and take it out of 10th gear,you have to rev the motor up to 1600rpm's to get it back in gear,if you have the clutch pushed in while doing it,the only thing your reving up is the motor,not the input shaft going into the transmission
transmission have 3 shafts inside
input shaft
output shaft
and counter shafts
you the driver need to get things spinning inside the trans at the correct speeds to mesh the gears togetter,you use the motor to do that
say you hit a hill and your RPM drops down and your loosing road speed
you push in the clutch to get the truck out of current gear,put it in nuetral,release clutch,rev up the motor to get the insides of the transmission spinning faster than before,push clutch back in and than shift into lower gear.
when acelerating
by shifting into nuetral and releasing the clutch for a split second,the drop in motor rpms will slow down the gears of the transmission,allowing you to get a higher gear.
don't sweat over it,thats what drivng school is for and a few million people have been known to master it.
zigzag

Answer:
JSG, informative post. Thanks
When you make fun of newbies, think back to when that newbie was you.

Answer:
Hey, I'm just a newbie, but I'm learning on about 10 different trucks, so here's my imput.
I've found that on some rigs, I don't have to use the clutch at all and things shift wonderfully. But on these two Volvos we have, they're so tight and stiff, that I almost always have to double-clutch IF I used the clutch at all for the first part of the shift. For whatever reasons (assuming I used the the first half of a double clutch), once you're out of the gear you were in and in the neutral zone, that second clutch movement makes the difference as the rpms are raised or lowered accordingly. Those two Volvos are very sensitive in that regard. If I don't use the clutch at all on the Volvos, it's smooth but exacting; they aren't forgiving!
On some of our trucks when I'm upshifting, if it's done correctly, I can move from one gear to the next (generally from the top of the "H" pattern to the lower part of the pattern) without any second clutching to drop the drop the rpms. But it has to be done exactly or you don't hit it dead on.
So, to sum up, I think a lot depends on the truck you're in and the skills you have to discern and work with the truck's flexibilities regarding the shifting process.
For the road,
Starkman

Answer:
I was over the road for about 2 months with burlington before they went bust and didn't tell me(thats another story but my trainer made me double clutch the whole time I was driving except when he was taking me home he would forget every rule he inforced and floated the gears. I now drive fro waste management, yes those crappy trash trucks. They are all worn in a little to much and only 5 speeds but you have to shift them the same. My boss told me not to use the clutch! I tried to but it didn't make a difference. So I float the gears which from what I here most people do. I even learned to put these trucks in 1st without the clutch and take off but I wouldn't reckomend it on big trucks. My advice is to do what your trainer and school says you will get used to double clutching but when you get your own truck your the one in control what ever works better for you.

Answer:
Originally posted by chevrolet_gt:
I was over the road for about 2 months with burlington before they went bust and didn't tell me(thats another story but my trainer made me double clutch the whole time I was driving except when he was taking me home he would forget every rule he inforced and floated the gears. I now drive fro waste management, yes those crappy trash trucks. They are all worn in a little to much and only 5 speeds but you have to shift them the same. My boss told me not to use the clutch! I tried to but it didn't make a difference. So I float the gears which from what I here most people do. I even learned to put these trucks in 1st without the clutch and take off but I wouldn't reckomend it on big trucks. My advice is to do what your trainer and school says you will get used to double clutching but when you get your own truck your the one in control what ever works better for you.
I used to see their ads all the time advertising leasing a truck from them with no money down and no credit checks. No wonder they went bust!
But anyway, I used to double clutch all the time, but now am getting the hang of shifting without clutching. The gears seem to come to better without clutching. The only time I clutch now is when starting or stopping. Sometimes I slip up though(pun intended)!

Answer:
Starkman,
"...But on these two Volvos we have, they're so tight and stiff, ..."
Are they new? Seems like the older the transmission, the easier it is to "mesh" the gears (zigzag) once they match. Same for pulling out of gear. My brand new transmission still needs a good little tug to get it out of gear, even when I'm riding the throttle to zero torque. So sometimes I stab the clutch a little when I pull it out.
Then I clutch a little bit again as I adjust the throttle to mesh the next gear. If the mesh is passing too fast, I can push the clutch a little more to grab the gear -- my foot's right there resting in the clutch slack on most of my shifts, I guess.
Got to be careful. If you float into a gear too fast while the mesh is passing too fast, you can send a major shockwave through your drive-train and rip-up your gears. Meshing gears directly from the crankshaft to the drive axel is best suited, I believe, to relazed shifting situations. On the other hand, agressive pedal-to-the-metal acceleration uphill onto a busy Interstate, you can shift faster with more clutch, at least that's how it is for me.
.
[This message was edited by Shuffler on October 29, 2002 at 03:39.]

Answer:
Originally posted by John X Neiser:
Try clutching once like you do in a car. You'll get tired of grinding gears. Truck transmisions are not syncronized.
Strike me as dumb, but I thought that everything but an old maxodine transmission was syncronized now days.
I couldn't shift a car transmission without the clutch and grinding gears to save my soul. Likewise, I couldn't use a clutch in a big truck, shoving the clutch in to shift gears would be truly awkward.

I guess shifting a truck transmission without clutching is just a thing that has become so rythmatic over the years of trucking, that the idea of pushing a clutch in seems silly.
I said all that to say this. Once the truck is rolling I have no need to clutch. Now in a car, if you want your car back in one piece you had better hope I push the clutch in.
************************************
Indiana RoadRunner
A legend in his own mind!

Answer:
Shuffler,
Yeah, I think they are, and all the symptoms you mentioned exists with both of them (the Volvos.) I have to really tug to get it out of gear to shift without the clutch. And yeah, I have to watch for the rpm match to avoid that sudden shock to the drive train. Hek, though, with as tight as those clutches are, I still find it easier in some cases to shift without the clutch.
For the road,
Starkman

Answer:
IR,
Never clutched in my ten-speed -- that thing was loose as a goose and it would mesh smoothly and silently -- swallow the gear with a slight nudge.
My new 9-speed is stiff and unforgiving, and you have to wrestle it in and out of each hole. It seems to be relazing a little as I put more miles on it, but the progress is slow, and my left knee hurts
.

Answer:
Hey Shuffler,
Boy, does my knee hurt too! It's right above the knee, where the tendon, I believe, connects to the cap, or something like this. I'm a little concerned, and I can say confidentally that when I get outta school, this boy's shifting without the clutch!
The Volvos are not new (around 750,000 miles on them), and their stiff as a board in the shifting department. The clutch is tight too, and . . . the knee hurts!
Well, school's in session . . .
Starkman

Answer:
Most of the equipment in commercial use out there won't have this problem.....I think....and you can probably look forward to this being one of those 'school truck' things. When you're actually doing 400+ miles per day, you won't spend much time shifting anyway.
Also, your posture in the seat makes a big difference. There might be a slight seat adjustment -- moving it a little higher or farther forward -- which changes the angle on your knee joint just enough to make a diference. In addition, you're probably using more muscle power than you really need right now, as your body gets used to this new auto-motor skill.
Try hinging your leg movement from your hip more, instead of extending your knee joint, and aviod 'pointing' your left toe on the clutch when you push it.
When you're not clutching, keep your left foot flat on the floor.

Answer:
Peterbilt379
Yes, double clutching you must do when driving a truck. 1st clutch allows you to move shifter to nuetral, 2nd clutch gives you ground speed to engine speed. But double clutching is stupid, waste of time, and waste of energy on yourself. Floating, which is shifting without the clutch, is no more than throttle pedal and involves no grinding of geers as long as you match ground speed to RPMs and you don't have to do this at high RPMs. Low range geers should be shifted 1250-1450 RPMs. High range 1400-1600 RPMs. And yes there are electronically syncronized transmissions out there. Try floating, it may take you a bit to learn, but it's easier on you and the truck.