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Old 05-24-2008, 05:00 AM   #1
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clutch or neutral

When coasting, which is better? Holding the clutch in on a standard transmission or actually putting it in neutral and letting out the clutch. Which causes less wear and tear on mechanical parts? I'm talking about a coast of 1/4 mile or more.
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Old 05-24-2008, 05:10 AM   #2
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That is a question that has been bugging me as well. I have several areas on my 49 mile (one way) commute to work where I can coast for well over a mile, so anyone with a good solid answer?
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Old 05-24-2008, 05:21 AM   #3
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Neutral. Holding the clutch pedal down will wear the throwout bearing. That's somewhat common knowledge, though I'm not experienced with it myself.

Besides, driver wear is important too. If you're too tired to operate the clutch smoothly after holding it in repeatedly, you're going to lose, and if you're too tired to P&G well you're going to lose.
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Old 05-24-2008, 05:23 AM   #4
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I use neutral, when I want to coast. Shifting has become second nature over the last 42 years of driving, so it takes some time to modify old proven habits.

Your throwout bearing which operates the clutch, is a sealed unit, when you keep the clutch pedal depressed you are using the throwout bearing. If the bearing goes bad you have to do the same work it takes to replace the clutch.

Neutral reduces friction losses in the transmission, by disconnecting the countershaft from the output shaft. Leaving it in gear keeps them both connected and looses some energy (not much but every bit counts).

Downshifting places stress on the synchros and gears, but its on the opposite side (of the synchro) as upshifting, so the wear pattern is different and not really relevant to the normal wear pattern that causes synchros to start to fail to do their job.

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Old 05-24-2008, 08:48 AM   #5
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I use neutral, when I want to coast. Shifting has become second nature over the last 42 years of driving, so it takes some time to modify old proven habits.

Your throwout bearing which operates the clutch, is a sealed unit, when you keep the clutch pedal depressed you are using the throwout bearing. If the bearing goes bad you have to do the same work it takes to replace the clutch.

Neutral reduces friction losses in the transmission, by disconnecting the countershaft from the output shaft. Leaving it in gear keeps them both connected and looses some energy (not much but every bit counts).

Downshifting places stress on the synchros and gears, but its on the opposite side (of the synchro) as upshifting, so the wear pattern is different and not really relevant to the normal wear pattern that causes synchros to start to fail to do their job.

regards
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yup thowout bearing can wear out before the clutch and thats a pain to do.

also if you know your vehicle well enough you can be in gear then let off the gass (ie start going down the hill) to where theres no foce being applied to the tranny from the engine side or wheel side so you can just NOT press the clutch in and pop the shifter in neutral saves the clutch, throwout bearing, pressureplate, and if you have a hydrolic clutch system.

also in neutral the engine is still turning the input shaft inside the tranny, thus moving the fluid around in the same direction as the wheels are turning the output shaft around, might make a whirl pool of fluid helping you coast
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Old 05-24-2008, 10:04 AM   #6
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Originally Posted by Kuripot View Post
When coasting, which is better? Holding the clutch in on a standard transmission or actually putting it in neutral and letting out the clutch. Which causes less wear and tear on mechanical parts? I'm talking about a coast of 1/4 mile or more.
keeping the clutch disengaged for long period of time only serve to wear out the pressure plate springs, throwout bearing, etc quicker. I always pop it in neutral. IHMO...
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Old 05-27-2008, 03:21 PM   #7
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also if you know your vehicle well enough you can be in gear then let off the gass (ie start going down the hill) to where theres no foce being applied to the tranny from the engine side or wheel side so you can just NOT press the clutch in and pop the shifter in neutral saves the clutch, throwout bearing, pressureplate, and if you have a hydrolic clutch system.
Yes, learn to drive without the clutch. I used to own a '93 Saturn SL2 with a manual transmission, learned to drive without the clutch both up and downshifting.

It is so ingrained in me that when I drive a stick nowdays (a treat as I own 2 automatic trans cars) that I shift without the clutch.
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Old 05-27-2008, 08:33 PM   #8
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If you are going to be coasting for a mile or more, I would throw it in neutral and kill the engine. Infinite mpg!
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Old 05-28-2008, 08:24 AM   #9
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If you are going to be coasting for a mile or more, I would throw it in neutral and kill the engine. Infinite mpg!
Also remember that in some cars when coasting in gear they automatically shut off fuel to the motor, so you get infinite MPG that way. You can't coast as far because of compression braking from the motor, but if you coast in neutral or with the clutch in you are burning gas to keep the engine idling. It depends on your driving style, the hill and other factors as to which saves you more gas, but it is something you may want to check.
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Old 05-28-2008, 09:39 AM   #10
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Remember that coasting in neutral is illegal in some states. In Washington RCW46.61.630 says this:

"(1) The driver of any motor vehicle when traveling upon a down grade shall not coast with the gears of such vehicle in neutral."

Since I have a new throw-out bearing in my Subaru, and it already has almost 200k on it, I choose to wear the throwout bearing. It is also safer in an emergency where you need power, since you can simply let out the clutch and stomp the gas. Of course by the letter of the law, that only applies to "down grades" so PNG on level ground should be a different story.
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