Chuckdiesel
Full Access Member
Well I have been getting good at shifting now without using the clutch and was wondering if that really is not a good idea? Shure gives my foot a break
Shifting W/O clutch
- Thread starter Chuckdiesel
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Mr_Roboto
Full Access Member
The one problem with floating gears is that it can cause the splines on the input shaft to widen where the clutch is when it's released. This is a bigger problem on OTR trucks that can go hours without stopping.
When I went through truck driving school we were shown a trans that the splines were so screwed up that the clutch would no longer release, because there was a "step" in the splines.
I don't see a big problem with floating gears if you can do it smoothly.
When I went through truck driving school we were shown a trans that the splines were so screwed up that the clutch would no longer release, because there was a "step" in the splines.
I don't see a big problem with floating gears if you can do it smoothly.
on a t18/19 its ok. on a ZF5....its a really bad idea. on the backside of the syncros of a ZF, there is a sintered metal friction material that is thinly deposited on the syncro body. clutchless shifting take the life out of the syncro very quickly.
argve
Resident Fruitcake
When my nephew was with me and seen me shifting without touching the clutch he very nicely mentioned that it's very very ******* the synchros and he advised against it - he had just gotten done with his class on manual trans in auto mech school. So I have been using the clutch ever since... He has a reason to try and curb my bad habits because he knows that he will be the one that is forced to perform the labor for free so... (isn't family great)
swampdigger
Full Access Member
My T19 is too much of a ***** to allow it. All my Rangers didn't complain too bad, but not this truck... if the RPMS are off even a little bit it grinds, and that noise just sends shivers up my spine.
82F100SWB
Full Access Member
My T19 floats the gears quite nicely, a ZF, not a good idea, they don't shift nicely without the clutch(and not that great with it IMHO,) and it is vey ******* them.
swampdigger
Full Access Member
Hmmm.... me thinks I just need a bit more practice then
Freight_Train
Traitor to the brotherhood
Doing this in any transmission is a big no no.Especially trannies with Sycros.First off,they were designed for use with a clutch.That is the reason the Sycros are there.Second,what happens to all that metal that you are grinding off the Syncos every time you don't clutch.It is floating around inside the tranny galling up bearings and chewing up gears.This ain't no peterbilt we are driving.And even if it was your still supposed to use the clutch.
Diezel_Cowboy
It's not like a real ***!
There is a fine line between doing damage and simply shifting without a clutch...........Let me elaborate .............if you can shift it without any grinding..............then its ok.........if you hear grinding then it is wearing out parts
There seems to be some kind of lure which comes from professional drivers that seems to suggest that you never need to use your clutch. I've had truck driver friends tell me of people who NEVER used it, including starting from a stand still. Now I don't know a lot about large truck transmissions, and I suppose if the gears are bigger, and low enough that you might be able to get away with this, BUT... I do have a good sense of engineering and manufacturing, and I challenge you to find me ANY operators manual that encourages the use of shifting without a clutch. You find me a manual that says "The clutch is to be used in extreme emergencies only, and it's use should be avoided at all cost" and I'll eat my shorts. I've never been able to understand the fascination of not using it. To be honest, if your foot or leg gets tired, you probably should have an automatic. No offense intended, and there was no reason not to ask this question. I'm just throwing out my 2 cents. I have heard they have started to develop "automatic manual transmissions" in the trucking industry where there is some kind of computer controlled clutch and shifting action going on, and that sounds really amazing. Nothing like taking a simple system and making it as complicated as you can. 
Mr_Roboto
Full Access Member
Well in general big truck transmissions are not synchronized, you double clutch to synchronize the gears. And once you learn to synchronize the gears via double clutching, it gets real easy to just "float" the gears over.
The only trucks I've seen start out without the clutch are UPS trucks (the smaller box trucks, not semi's). I assume they do this simply to get moving faster.
Synchronizers are basically tiny little clutches, made to raise or lower the speeds of the gears to match. If your engine speed is already matched to the road speed for the gear you are going into, the synchronizers don't have to do anything.
The only trucks I've seen start out without the clutch are UPS trucks (the smaller box trucks, not semi's). I assume they do this simply to get moving faster.
Synchronizers are basically tiny little clutches, made to raise or lower the speeds of the gears to match. If your engine speed is already matched to the road speed for the gear you are going into, the synchronizers don't have to do anything.
the key seems to be once the engine and tranny line up speed wise it will drop right in. the trouble is what are you doing until they line up? i am no pro but when i do it i rest some weight on the shifter until it drops in smoothly. it feels smooth but the weight i put on the shifter is placing strain against the syncronizers and they are trying to line things up. they cant because they are not able to overcome the engine speed instead of just the clutch disk when you do depress the clutch.
so i can see where you would be silently smoking your syncros until you do find that sweet spot unless you can hit it spot on every time.
so i can see where you would be silently smoking your syncros until you do find that sweet spot unless you can hit it spot on every time.
Exactly. If your transmission has synchronizers, it has these little guys in there to speed up/slow down the input and counter shafts in the transmission to mesh the sliding gears between them and the output shaft.
The synchro cannot affectly change the output shaft speed because this would require changing the speed of the entire vehicle, so they speed up/slow down the input shaft speed(and thus counter shaft speed) to achieve this. If the input shaft is disconnected from the engine via the clutch being disengaged, then the synchros only have to speed up/slow down various trans parts and the clutch disc. If the clutch is not disengaged, the synchros will have to affect the speed change upon the trans parts, the clutch disc, the flywheel, and the entire rotating assembly of the engine.
One can easily see the difference in load there and why floating the clutch can quickly wear synchros. If the operator is spot-on with the shift, then the synchros will live because no speed matching will be necessary, but slightly off and the synchros are screaming for mercy...
One thing to realize here is that unlike a non-synchronized gear change, a slightly off-speed synchro'd change with out disengaging the clutch will not be obvious to the operator. The operator will not realize the synchro just had to do the last little bit of speed matching, atleast not until the synchro is eventually worn out. With non-synchronized transmissions, the operator knows if it was done right.
Ken
There seems to be some kind of lure which comes from professional drivers that seems to suggest that you never need to use your clutch. I've had truck driver friends tell me of people who NEVER used it, including starting from a stand still. Now I don't know a lot about large truck transmissions, and I suppose if the gears are bigger, and low enough that you might be able to get away with this, BUT... I do have a good sense of engineering and manufacturing, and I challenge you to find me ANY operators manual that encourages the use of shifting without a clutch. You find me a manual that says "The clutch is to be used in extreme emergencies only, and it's use should be avoided at all cost" and I'll eat my shorts. I've never been able to understand the fascination of not using it. To be honest, if your foot or leg gets tired, you probably should have an automatic. No offense intended, and there was no reason not to ask this question. I'm just throwing out my 2 cents. I have heard they have started to develop "automatic manual transmissions" in the trucking industry where there is some kind of computer controlled clutch and shifting action going on, and that sounds really amazing. Nothing like taking a simple system and making it as complicated as you can.
I drove big trucks for a lot of years, on a non synchro box, it is easier to shift without the clutch and does not cause any wear on splines..if you are doing it correctly, in fact, it causes the least amount of wear and it makes it a whole lot easier to find a gear on steep hills, if you waste your time double clutching ( especially on the older trucks with a lot of gears ) you'll loose 2-3 gears at a time, plus if you are buying the clutches and throwout bearings for those things, you dang sure don't want to use them any more than absoloutely necessary.
Back when I learned to drive those beasts, the guy had a tire thumper in his hand and said" anytme you go for that clutch other than to stop or go, I'll whack your left leg". I don't know if he really would have, but it was his truck. I learned fast
Synchro boxes on the other hand, need the clutch action or you'll trash the synchros, they are made out of softer metal and won't hold up to being bounced around under load, and they have little springs that keep a little tension on them so you really can't truly float gears with one.
On a funny side note, I taught my wife to drive a stick in a Freightliner. She had no bad habits from driving a stick in a car and learned faster than anyone I've taught before and was floating gears like a pro in no time, but when I tried to teach her to drive a stick in a car, it was a disaster ( 4 year old in the back seat exclaiming "is it over yet "
----------Robert
