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Everywhere I read, people say to shift into neutral at a light, and some say just to hold the clutch in which I understand unnecessarily wears the throw out bearing.

Why can you not just shift to first and use the brake to keep the car from moving like all automatics in Drive, without touching the clutch? Is there something different about manual transmissions that makes the car stall when doing this? If so what is the difference?

NULL
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    What? Have you ever driven a vehicle with a manual transmission? What is your maintenance or repair problem? – cory Dec 09 '16 at 16:48
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    Maybe the real question is not "why can't you use the brake at a stop like an automatic", but "why can an automatic stay stopped without stalling like a manual?" – Trevor D Dec 09 '16 at 18:36
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    Let's have the 1950s remind us how things work. – J... Dec 09 '16 at 19:43
  • The only manual that I've ever driven that could be left in 1st gear at idle without holding the clutch that didn't stall was my Hyundai Tiburon on the stock clutch... Ever other manual I've ever driven (Including that Tiburon after I upgraded the clutch) would stall at idle in 1st gear... – Taegost Apr 18 '17 at 12:39

2 Answers2

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Why can you not just shift to first and use the brake to keep the car from moving like all automatics in Drive, without touching the clutch?

In a manual gearbox, the clutch (when you release the clutch pedal) is a 'hard' coupling that does not allow any slip. So the engine will try to move the car against the brakes, it will lose that battle (brakes are more powerful than the engine), and the engine will stall.

In an automatic gearbox, the torque convertor is basically a box filled with oil and 2 impellers. One driven by the engine, one connected to the gearbox. The 2 impellers can have different speeds, so the engine won't stall when you stop the car, leave it in gear and use the brakes to hold it.

Hobbes
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    Not sure how this accounts for the thought of "putting it into neutral at a light" ... I think the OP's question has more to do with damage differences to the transmission between putting it in neutral or just holding the clutch pedal down. – Pᴀᴜʟsᴛᴇʀ2 Dec 09 '16 at 15:23
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    Actually this was just what I was looking for, sorry if my wording was confusing to others. Thank you so much this makes complete sense now! – NULL Dec 09 '16 at 15:28
  • @Pᴀᴜʟsᴛᴇʀ2 : I've edited my answer to clarify. – Hobbes Dec 09 '16 at 15:43
  • FWIW I came here interested in the some say just to hold the clutch in which I understand unnecessarily wears the throw out bearing part, and created an account here to leave this comment. Or is that answered elsewhere on this site? (EDIT: nevermind, found it) – Mathieu Guindon Dec 09 '16 at 19:06
  • If it stalls in that case for that reason, then what about when you are not holding the brake, and do not have the parking brake engaged? Why does it stall then? – Pysis Dec 09 '16 at 21:40
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    If you release the clutch suddently with the car stopped and the brakes off then the car will speed up suddenly and the engine will slow down suddenly. If the engine is slowed down below it's stall speed then the engine will stall. – Peter Green Dec 09 '16 at 21:59
  • @Mat'sMug Thanks :P I came here for that exact reason as well! – Blackhawk Dec 09 '16 at 22:28
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The advise to put the transmission in neutral at the light, and then release the clutch has been around for ages. There are arguments on both sides of the fence. I used to do that all the time with my cars and trucks. As I got older and arthritis on my left knee bothered me, I do it less. In fact the 99 VW I drive every day, I seldom put in neutral, except at a long light or a train crossing.

The idea was that the throw out bearing, which is under stress with the pedal pushed in, and the throw out bearing or release bearing is working with the pedal in.

If the transmission is put into neutral, and the pedal released, then there is no pressure on the bearing, and it will not wear.

For what it is worth, the current daily driver has 340k miles and is on it's original clutch, and I have not had to replace the throw out or release bearing.

So I am not really sure of the practical impact of all this, but I do sometimes take the pressure off the clutch and put the transmission in neutral at long waits, or where perhaps for safety reasons (hate to slip off that pedal and plow into the 9:22 Conrail).

EDIT ADD Ah, one more thing...there is a downside of putting the transmission in neutral all the time. First you are actuating the clutch twice, instead of once. Second, when you let out the clutch pedal with the transmission in neutral, part of the transmission starts spinning. This is twofold, in that the clutch just did a little work, but not as much as getting the car going, by getting the transmission turning. And the second related issue is that probably when you press in the clutch and put the transmission into first, you will do so quickly and servos (little brakes on shafts) will have a small amount of wear as they get things to match speed. Ancient transmissions may not have had all those servos, and had to be "double clutched" in some shifting operations.

Again, you might consider the neutral setting for longer wait times, or where safety is a consideration.

mongo
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  • Your first paragraph is interesting, as I find it easier on the knee (and hamstring) to change into neutral and release the clutch rather than holding the clutch down for ages - perhaps my cars have had heavier clutches than yours! – Nick C Apr 21 '17 at 09:12
  • Clutch pressures vary. My tractor has a much higher force needed than the car, that's for sure! The car mentioned above is a VW TDI, and since the clutch handles a fair amount of torque for it's size, I would expect the foot force to be on the high side. I have not measured it, though. Just recognize that there is a "price" for putting the transmission into neutral, though. – mongo Apr 21 '17 at 11:34