clutch or no clutch

[JFortner5]

Thanks that cleared it up guys. Im sorry to hijack, but I guess it was kind of on topic.

 

[counter]

well i guess im still a little confused! some of you guys clutch, yet others just feel the gears!as i said, ive only drivin cars and light trucks, doin the no clutch thing! just wanta know whats best!!!

 

[JFortner5]

From what I gather its personal preference. Double clutching gives you a little more time to make the shift. If you can shift without the clutch, do it. No need to wear out your left leg and your clutch.

Disclaimer- I am not experienced and haven't ever driven a heavy truck either, so my opinion is based on my decent understanding of how transmissions work.

 

[willie59]

No need to wear out your left leg and your clutch.QUOTE]


That has as much to do with it as anything. When your driving a truck all day long, making as many shifts as you do, mashing that clutch gets old. And the clutch on a heavy truck is just a little bit more stiff that that of a vehicle like a car. You don't even like to hold the clutch in at a red light, wears out the leg. You learn to sit there in neutral, and when the light turns green, you put the clutch down on the clutch brake to stop the shaft, and put it in gear. Once you get going, you leave the clutch alone, shift, and drive.

 

[Red Bank]

I think ATCO is right, the one thing I have noticed driving is, to me, double clutching is more of a timing procedure than actually using the clutch to work. What I mean by that is it allows the rpms to fall down to where the transmission will shift right in. When I am driving a new truck, or if I get in a bind or out of synch I will double clutch, but I have noticed that I am not actually engaging the clutch I really just take the free play out. I have also noticed that when I ride with our drivers, everyone has a different style, some will run the rpms up more than I would or some will shift quicker than I would, as long as it works, the transmission shifts, the driveline does not clunk and the truck moves down the road then however it got to that point that it works is right.

 

[JFortner5]

The way I see it is it doesn't matter what you do as long as shafts in the transmission match speeds.

The only benefit I could see from double clutching would be a little more time to make the shift, if thats really a benefit. Im not sure if its been said already, but I would think with the clutch engaged the input shaft on the transmission would slow down faster with the engine. I know those shafts arent light, so by disengaging the clutch during a shift they would "freewheel" a little longer and give you more time to grab the next gear.

 

[willie59]

JFortner5, your right in the middle of understanding this. This "clutch or no clutch" thread has become one crazy and informative thread talking about something we do all day long with out giving much thought to it. As Red Bank stated; "as long as it works". I thought I'd throw a post in here for anyone who has never driven a heavy truck transmission to try and explain, partly, why we do what we do shifting these things. Aside from getting tired of mashing the clutch pedal all day :Banghead, maybe part of the reason we all learned to shift by leaving the clutch engaged (no clutch) is because of a simple principle of physics...inertia. JFortner5 has figured this out. Unlike a car tranny, the gears and shafts in a truck transmission are large, and their mass creates a "flyweel effect" of the moving parts, which is where inertia comes in, the law of physics that says that anything in motion will remain at it's current speed until it encounters an external force. To keep things simple, we won't include the friction of bearings and gears meshing, just a basic overview of how inertia affects shifting a truck tranny. Let's say your in a loaded truck, and you run a gear until the engine is on the governor. It's time to shift to the next gear. At that point, if you just pushed in the clutch and tried to shift to the next gear, you'd get nothing but grinding of gears. That's because the gears/shafts are subject to inertia, they'll keep turning at their current speed until some external force slows them down to engage the next gear ratio. Thankfully, we have an external force that we have control of...the engine. But in order for us to use the controlling force of the engine, it has to be coupled to the transmission...the clutch. Here's how it works; rev the gear to the engine governor, don't mess with the clutch pedal, pull the tranny in neutral, then let off the throttle. The engine is now coupled with the tranny. The engine rpm drops quickly when you let off the throttle pedal and, likewise, quickly slows the turning of the tranny shafts, which then allows you to mesh the gears. At this point, JFortner, that's where the double clutch comes in. The double clutch is this; rev the gear, push in the clutch to pull lever into neutral, then clutch out to let the engine slow down the tranny, and at just the right rpm, push in the clutch to mesh the gear. It's not long before you get the feel of things and you just forget the clutch altogether and control the shifting using nothing but the throttle pedal. And your left leg thanks you.

 

[JFortner5]

I really want to try and drive one. I think I've got the basics, I just want to try and actually do it.

 

[440chevy]

I really want to try and drive one. I think I've got the basics, I just want to try and actually do it.

As long as you remember to pull it out of gear while your still accelerating the rest isn't to bad pending some grinding. I got my truck last October and I parked my pickup and bobtailed everywhere for about 2 weeks and just had a blast. I had been driving a dump truck with an Allison for 3 years by then so the size never bothered me, which helped.

As far as the clutch issues, most people I talk to just do whatever they feel like doing, which is the same for me. When I'm pulling a steep hill with my 13 spd I just feel like double clutching helps when I'm going through 1-4, but when I get into hi range with the splits I don't find it necessary anymore. I definitely think that one should be able to both efficiently.

 

[Red Bank]

As long as you remember to pull it out of gear while your still accelerating the rest isn't to bad pending some grinding. I got my truck last October and I parked my pickup and bobtailed everywhere for about 2 weeks and just had a blast. I had been driving a dump truck with an Allison for 3 years by then so the size never bothered me, which helped.

As far as the clutch issues, most people I talk to just do whatever they feel like doing, which is the same for me. When I'm pulling a steep hill with my 13 spd I just feel like double clutching helps when I'm going through 1-4, but when I get into hi range with the splits I don't find it necessary anymore. I definitely think that one should be able to both efficiently.

Which brings us to the next section of the class:drinkup Changing gears when loaded and empty, or when bobtailing or pulling a trailer, as Atco pointed out above the weight of the load will also weigh into the inertia equation. I think the hardest thing to learn for me was to shift without grinding when I was bobtailing a tractor. When I am loaded I feel like it is a whole lot easier to shift, whether using the clutch or not.

 

[Scrub Puller]

JFortner5, your right in the middle of understanding this. This "clutch or no clutch" thread has become one crazy and informative thread talking about something we do all day long with out giving much thought to it. As Red Bank stated; "as long as it works". I thought I'd throw a post in here for anyone who has never driven a heavy truck transmission to try and explain, partly, why we do what we do shifting these things. Aside from getting tired of mashing the clutch pedal all day :Banghead, maybe part of the reason we all learned to shift by leaving the clutch engaged (no clutch) is because of a simple principle of physics...inertia. JFortner5 has figured this out. Unlike a car tranny, the gears and shafts in a truck transmission are large, and their mass creates a "flyweel effect" of the moving parts, which is where inertia comes in, the law of physics that says that anything in motion will remain at it's current speed until it encounters an external force. To keep things simple, we won't include the friction of bearings and gears meshing, just a basic overview of how inertia affects shifting a truck tranny. Let's say your in a loaded truck, and you run a gear until the engine is on the governor. It's time to shift to the next gear. At that point, if you just pushed in the clutch and tried to shift to the next gear, you'd get nothing but grinding of gears. That's because the gears/shafts are subject to inertia, they'll keep turning at their current speed until some external force slows them down to engage the next gear ratio. Thankfully, we have an external force that we have control of...the engine. But in order for us to use the controlling force of the engine, it has to be coupled to the transmission...the clutch. Here's how it works; rev the gear to the engine governor, don't mess with the clutch pedal, pull the tranny in neutral, then let off the throttle. The engine is now coupled with the tranny. The engine rpm drops quickly when you let off the throttle pedal and, likewise, quickly slows the turning of the tranny shafts, which then allows you to mesh the gears. At this point, JFortner, that's where the double clutch comes in. The double clutch is this; rev the gear, push in the clutch to pull lever into neutral, then clutch out to let the engine slow down the tranny, and at just the right rpm, push in the clutch to mesh the gear. It's not long before you get the feel of things and you just forget the clutch altogether and control the shifting using nothing but the throttle pedal. And your left leg thanks you.

Yair...dunno about the modern trannys but don't quite agree there ATCOEQUIP when you say "pull the tranny into neutral, then let off the throttle..." on the old two stick Macks and Fodens and what all it was all kinda one action, you had to let off the throttle in order to take the load off the gears so you COULD pull the stick into neutral. Does that make sense to you?

Difficult to describe this stuff per medium of just words, you are doing pretty good I reckon.

 

[willie59]

Yair...dunno about the modern trannys but don't quite agree there ATCOEQUIP when you say "pull the tranny into neutral, then let off the throttle..." on the old two stick Macks and Fodens and what all it was all kinda one action, you had to let off the throttle in order to take the load off the gears so you COULD pull the stick into neutral. Does that make sense to you?

Difficult to describe this stuff per medium of just words, you are doing pretty good I reckon.

You darn skippy, Srub Puller, it is a bit difficult to put this stuff into words. I guess I'm doing it because I find it to be an entertaining challenge. Like I said, this is stuff we do all day long and don't give it a thought. It's a little tougher tryin' to 'splain it in writing. I guess that one description got a little vague. I was trying to describe an upshift, your absolutely right about letting off the throttle enough to relieve the pressure on the gears is the first part of the process, then the part I was trying to explain is "you pull it in neutral and let the throttle off so the engine revs go down to the proper rpm for meshing the next gear." When it get's there, drop it in gear, and throttle back on. That's what I was trying to say. I'll keep working on it.

 

[counter]

are you guys tellin me, the over the road guys just find the gears, but dont need to clutch?

 

[willie59]

are you guys tellin me, the over the road guys just find the gears, but dont need to clutch?

Naw, never said we don't "need" the clutch, just in many circumstances we don't "use" the clutch. You just do whatever works best for ya'.

 

[440chevy]

are you guys tellin me, the over the road guys just find the gears, but dont need to clutch?

I would think one could safely say most truck drivers only use the clutch when starting out. Other than that it's all about using the gas pedal to shift.

 

[Bob Horrell]

Then we can move on to advanced shifting techniques (without the clutch of course). For instance when bobtailing or driving without a load, there is no need to use all the gears. That is when you skip shift. When my dumptruck is empty I only use 4 or 5 gears depending upon circumstances. When doing this, you have to wait longer for the gears to slow down to match rpms since you are skipping gears. If going down hill, you may be able to skip several gears at a time.
Another "advanced" technique is when pulling a heavy load up a hill in the lower gears - 1st to 2nd or 2nd to 3rd or even 3rd to 4th. What happens during normal shifting is that the truck speed slows quicker than that big ole engine can wind down so you can't make the shift. There are 2 solutions. One is to use the engine brake to slow the engine quicker (burp shifting), which if done wrong can damage u-joints. The second, and the one I prefer, is turning on the fan with the manual switch. The fan helps to slow down the engine quicker. I find in most cases, if I don't rev the engine up too high, the fan does the trick just fine - I guess I would call it short shifting with the fan.
These are things that can be learned once a driver has the timing down on regular shifting. For those that enjoy driving trucks, this just adds to the fun factor.

 

[440chevy]

Then we can move on to advanced shifting techniques (without the clutch of course). For instance when bobtailing or driving without a load, there is no need to use all the gears. That is when you skip shift. When my dumptruck is empty I only use 4 or 5 gears depending upon circumstances. When doing this, you have to wait longer for the gears to slow down to match rpms since you are skipping gears. If going down hill, you may be able to skip several gears at a time.
Another "advanced" technique is when pulling a heavy load up a hill in the lower gears - 1st to 2nd or 2nd to 3rd or even 3rd to 4th. What happens during normal shifting is that the truck speed slows quicker than that big ole engine can wind down so you can't make the shift. There are 2 solutions. One is to use the engine brake to slow the engine quicker (burp shifting), which if done wrong can damage u-joints. The second, and the one I prefer, is turning on the fan with the manual switch. The fan helps to slow down the engine quicker. I find in most cases, if I don't rev the engine up too high, the fan does the trick just fine - I guess I would call it short shifting with the fan.
These are things that can be learned once a driver has the timing down on regular shifting. For those that enjoy driving trucks, this just adds to the fun factor.

I've heard of burp shifting but no one ever told me what happens when it goes wrong. Haven't heard of using the fan, I'm looking forward to trying that trick out. Thanks.

 

[counter]

keep the education comming guys! im sure im not the only moron here ,to want to know how you pro-drivers do every day!

 

[Scrub Puller]

Then we can move on to advanced shifting techniques (without the clutch of course). For instance when bobtailing or driving without a load, there is no need to use all the gears. That is when you skip shift. When my dumptruck is empty I only use 4 or 5 gears depending upon circumstances. When doing this, you have to wait longer for the gears to slow down to match rpms since you are skipping gears. If going down hill, you may be able to skip several gears at a time.
Another "advanced" technique is when pulling a heavy load up a hill in the lower gears - 1st to 2nd or 2nd to 3rd or even 3rd to 4th. What happens during normal shifting is that the truck speed slows quicker than that big ole engine can wind down so you can't make the shift. There are 2 solutions. One is to use the engine brake to slow the engine quicker (burp shifting), which if done wrong can damage u-joints. The second, and the one I prefer, is turning on the fan with the manual switch. The fan helps to slow down the engine quicker. I find in most cases, if I don't rev the engine up too high, the fan does the trick just fine - I guess I would call it short shifting with the fan.
These are things that can be learned once a driver has the timing down on regular shifting. For those that enjoy driving trucks, this just adds to the fun factor.

Yair... it's a different world you blokes live in....and I can't tell you how much I enjoy these forums. Please excuse my ignorance Bob Horrell but do you mean turning on the "manual switch" of a thermostaticaly controlled electric or hydraulic engine cooling fan?

If so I would be curious as to the ambient temperatures in your area and what percentage of the time the fan actualy runs.

What is the operating rev range of the modern truck engine as I am having difficulty coming to grips with some of the techniques.

As mentioned in other posts I mostly drove two stick Macks...from 6-71engined NR's to a variety of "B" Models, the ones with the triplex box were best for our normal bush road work. None of them would lug and you had to keep them on the boil...a usable rev range of about three hundred kept you busy on the sticks.

 

[Bob Horrell]

Scrub Puller, actually the first big truck I ever drove many years ago was a twin stick. It was in the Mountains in Colorado. You had to learn real quick with the steep and winding mountain roads. I probably couldn't do near as well today with a twin stick. It has been a long time.
Yes, I was talking about the engine fan. I have an extra large radiator and engine fan. The fan really slows down the engine quick.
The summer temps. where I live average mid 90degrees farenheit to above 100. I drive in a very hilly area. My fan only comes on automatically on hills or if I am going real slow on a dirt road. Of course the more the load, the quicker the fan will come on.
My truck has a 500HP Detroit Diesel. Max rpm is just over 2,000 rpms with the max torque at 1500 rpms. Detroit spec sheet says max fuel mileage is at 1400 rpms.