I drive a stickshift. When I pass over the top of a long steep hill on the highway, rather than have the engine crank
along at 3500 rpm, I shift into neutral and coast down. I figure this saves gas. Then after I reach the bottom and my
speed almost gets to where I’m going too slow, I put it back
in fourth and ease out the clutch pedal.
Is this OK? Or will I damage my transmission?
It’s fine. You won’t damage your transmission.
Assuming you engage fourth at a reasonable speed and that you do declutch gently, I can’t see any harm in it at all.
As to whether you should be coasting in neutral in the first place, driving instructors tend to frown on it.
No problem provided that the speed is within the range where you would normally use fourth gear.
I doubt if you’re saving fuel, by the way. Your fuel consumption at no load at 3,500 rpm won’t be that different to the fuel consumption at idle. And then you have to engage the transmission and accelerate to come back up to speed.
DON’T do this. As hybernicus said, you’ll save virtually no fuel. The downside is much worse: no traction. The engine idles, and is incapable of transferring power to whichever wheels are driven. Therefore, the car has less mechanical grip. This can result in dangerously unpredictable roadholding (or rather: lack thereof) when making a sudden evasive manoeuver (say a crossing deer).
I’d say your life and even your insurance premium are more valuable than the possible $0.10 of gas you save.
In some States in the US it is called “freewheeling”, and is technically illegal to do so. So don’t ever admit to doing it in an accident unless you feel responsible to tell all.
Actually, you don’t even need the clutch to do that. An old trucker taught me a trick to shift without the clutch, so you never step on the pedal except when starting & stopping.
When you’re using engine power to increase or maintain speed, the gears that combine to create “1st, 2nd, 3rd” etc. are wedged against each other. On the input shaft, the engine tries to accelerate one gear, while on the output shaft the driveline tries to decelerate the opposite gear. If you mark the faces of each gear “A” & “B” so that all the “A” sides face into a clockwise rotation and “B” into a counterclockwise rotation, two intermeshing gears make contact on matching “A” or “B” faces, depending on whether you speed up or slow down. Under power, the “A” faces of the input gears always push the “A” faces of the output gears, and under drag, the “B” faces of the output gears push on the “B” faces of the input gears.
Next time you’re driving, step on the gas hard at any speed, and try to pull the stick out of gear into neutral, without using the clutch. Tough, isn’t it? The pressure between the “A” faces creates enough friction to keep it in gear. Now run up to 50 or 60 mph and downshift to third. Once it’s in gear and the motor is revved up, stay off the gas and as the car decelerates, try to pull it out of gear. Same thing, but this time it’s the “B” faces wedged together.
Now try a new variation. Under hard acceleration, try to pull the stick out of gear, gently. Once you have a good feel for the resistance, keep pressure on the stick, and easy slowly off the gas. You eventually reach a gray area between acceleration & deceleration, where the engine speed is matched to the driveline speed such that there is no pressure on EITHER the “A” or “B” faces. At that point, you can pull it out of gear with one finger.
Once you have an idea of what engine speed matches what ground speed for a given gear, you can use this same equilibrium point to shift INTO gear without the clutch. If your engine spins at 3000 RPM in 3rd gear at 45 mph, then if you’re in neutral, coasting at 45, you can bring the engine up to 3000 RPM and slide it into 3rd without ever touching the clutch, and probably without making any gear noise (once you get really good). Ever try to stick it in gear without the clutch and hear a “grinding” noise? It’s just two gears rotating at different speeds, making several impacts a second, but it’s so fast they sound like one big whine. As you get those gear speeds closer together they may tap a little, but you can actually begin to feel the individual impacts. The trick is to slow those impacts down enough to keep them from doing damage.
“Why bother” you ask? Simple… if you can learn to do this, you can also learn to minimize the stress on your clutch anytime you use it to shift. Anytime you step on or off the clutch pedal while the engine is providing power or the driveline is providing drag, you make the clutch slip against the flywheel. If you manually match speeds, you minimize clutch slip, and prolong it’s life. On the other hand, if you take too long learning the feel for the clutchless shift, you’ll wear out the gears, which are harder to replace.
It is illegal in Florida to coast down a hill in neutral. You could be given a ticket if somehow the officer KNEW you were doing it. How he could ever know is beyond me.
Sleepy Weasel, thanks for your post. I have heard of this technique, but never heard how or why it worked. I was going to post that as a GQ, actually.
Now well see if I can get the balls to try in the Pimpmobile (aka '94 corolla).
Florida has hills?
No problem. I learned the “Feel” for it by just slipping it in and out of the same gear first, trying to keep the engine speed steady. That might make it easier on you.
I seem to remember the same “no coasting” law in CA, but I’ve been in TX for about 5 years, so I’m a little rusty on the California Vehicle Code. Texas has a version that says it’s against to let go of the reins when inside the city limits of an incorporated area, or when herding cattle.