Clutch safety switch purpose?

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Hello everyone, for years I thought that clutch safety switches are a relatively useless and somewhat annoying "feature". I understand that if someone accidental leaves the transmission in gear and tries to crank the engine, the vehicle will jump forwards/backwards if the brakes or parking brake isn't applied and could cause injury or damage, although the likelihood of any incident resulting in severe injury or significant property damage is arguably pretty low. Forcing someone to disengage the clutch to crank the engine almost eliminates the possibility of the vehicle moving while cranking.

However, my big problem with that design is that it is IMO not effective at accomplishing it's intended purpose. Here's why: Checking to make sure the trans is in neutral before cranking the engine is obviously good practice. However, sometimes people forget. But if someone forgot to make sure the trans is in neutral before cranking the engine, do you think the odds of them remembering to make sure the trans is in neutral after starting the engine before releasing the clutch is any better? As many people as I have seen and heard of who pressed the clutch to start the engine and promptly released the clutch without realizing the trans is still in gear, I don't think so.

My other problem with that design is it is just plain inconvenient. Who wants to press the clutch every time they start the engine? I know it's not usually a big deal, but it's still an unnecessary inconvenience for IMO not much or any benefit. This is especially true when the passenger of the vehicle needs to start the engine for heat or AC when the driver isn't currently in the vehicle for whatever reason. I personally know several people who have had this problem at some point.

In my opinion, a better, more user friendly, and more effective method of preventing the vehicle from being started in gear would be for the manufacturers to implement a neutral safety switch like on automatic transmissions. That would virtually eliminate the possibility of the vehicle moving when started until the driver actually puts the trans in gear and releases the clutch rather than simply until they carelessly release the clutch as soon as the engine starts. This solution would also have the advantage of working with remote starts unlike the clutch safety switch, which is typically simply bypassed when a remote start is installed. Being able to start the engine from the passenger seat or without getting in the car would be a benefit too.

If anyone disagrees or has other thoughts, please let us know!
 
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I'm trying to envision how this Neutral Safety Switch would work on a Manual, Probably need 2 switches wired in series.....One for each Shift Rail.

When I'm diagnosing a Bolt Action vehicle & the Clutch Switch is aggravating my process, I just bypass the switch temporarily.
 
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I'm sure someone more creative than me could devise a solution, but how would the neutral safety switch be implemented? A manual gearshift is essentially floating in neutral, as opposed to making positive contact in a given position. You could have switches in each engaged gear position, but then the likelihood of failure would be increased, as you'd have 5/6/7 switches in play for one purpose. Also, challenges around serviceability of the switch(es) based on location could be a potential issue vs. the relatively easy to access clutch pedal.
 
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dishdude

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I've driven modern manuals that know what gear the transmission is in to the point it displays it on the dash.

I'm also dumb enough to have started a manual in gear with the clutch disengaged just to dump it and stall the engine 🤦‍♂️
 
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Yes mechanically detecting that a manual is in neutral is not simple. There are usually 3 shift rods and it would have to confirm that they are all in the center (neutral) position.

Usually I press the clutch and the brake and start, then select 1 or R and drive off. Having to shift to neutral is unnecessary.
 
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I’ve always by-passed it in every manual I’ve had. One was a 1 ton dodge with a 5.9 Cummins. Had a remote start on it too that I used all the time. Looking back it was kinda reckless but I was always very good about making sure it was in neutral when parking and also when starting with the key. Becomes second nature.
 
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I find them a bit annoying in a workshop situation - I just can't put my arm through the window to start the engine. Workshop policies are to always leave a gearbox in neutral, you just never know who is going to turn the key. Dangerous in a diesel, if it's in gear it will just keep rolling, spin the wheels before it stalls. Way back in the '50's, the MF35 had a start position on the high/low lever...it would only start in the neutral position, which was marked Start.
 
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I'm trying to envision how this Neutral Safety Switch would work on a Manual, Probably need 2 switches wired in series.....One for each Shift Rail.

When I'm diagnosing a Bolt Action vehicle & the Clutch Switch is aggravating my process, I just bypass the switch temporarily.

It's under the gear shift lever. It's also used for start/stop systems.
 
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Hello everyone, for years I thought that clutch safety switches are a relatively useless and somewhat annoying "feature". I understand that if someone accidental leaves the transmission in gear and tries to crank the engine, the vehicle will jump forwards/backwards if the brakes or parking brake isn't applied and could cause injury or damage, although the likelihood of any incident resulting in severe injury or significant property damage is arguably pretty low. Forcing someone to disengage the clutch to crank the engine almost eliminates the possibility of the vehicle moving while cranking.

However, my big problem with that design is that it is IMO not effective at accomplishing it's intended purpose. Here's why: Checking to make sure the trans is in neutral before cranking the engine is obviously good practice. However, sometimes people forget. But if someone forgot to make sure the trans is in neutral before cranking the engine, do you think the odds of them remembering to make sure the trans is in neutral after starting the engine before releasing the clutch is any better? As many people as I have seen and heard of who pressed the clutch to start the engine and promptly released the clutch without realizing the trans is still in gear, I don't think so.

My other problem with that design is it is just plain inconvenient. Who wants to press the clutch every time they start the engine? I know it's not usually a big deal, but it's still an unnecessary inconvenience for IMO not much or any benefit. This is especially true when the passenger of the vehicle needs to start the engine for heat or AC when the driver isn't currently in the vehicle for whatever reason. I personally know several people who have had this problem at some point.

In my opinion, a better, more user friendly, and more effective method of preventing the vehicle from being started in gear would be for the manufacturers to implement a neutral safety switch like on automatic transmissions. That would virtually eliminate the possibility of the vehicle moving when started until the driver actually puts the trans in gear and releases the clutch rather than simply until they carelessly release the clutch as soon as the engine starts. This solution would also have the advantage of working with remote starts unlike the clutch safety switch, which is typically simply bypassed when a remote start is installed. Being able to start the engine from the passenger seat or without getting in the car would be a benefit too.

If anyone disagrees or has other thoughts, please let us know!

When they started implementing this, it was only used before the vehicle was delivered. Delivery drivers used to ride the cars on and off trucks using the starter motor if the car wouldn't start. This prevented that from happening.

At the dealership we switched the car from showroom to client mode and the pressing of the clutch wasn't required anymore. Over the years that all changed.

The latest and greatest is: clutch must be fully pressed AND brake must be pressed AND gear lever must be in neutral.
 

555

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They don't have it in Europe. Maybe they do now?
Depressing the clutch is so ingrained in my head that it happens involuntarily before I start anything with an manual transmission.
 
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Hello everyone, for years I thought that clutch safety switches are a relatively useless and somewhat annoying "feature". I understand that if someone accidental leaves the transmission in gear and tries to crank the engine, the vehicle will jump forwards/backwards if the brakes or parking brake isn't applied and could cause injury or damage, although the likelihood of any incident resulting in severe injury or significant property damage is arguably pretty low. Forcing someone to disengage the clutch to crank the engine almost eliminates the possibility of the vehicle moving while cranking.

However, my big problem with that design is that it is IMO not effective at accomplishing it's intended purpose. Here's why: Checking to make sure the trans is in neutral before cranking the engine is obviously good practice. However, sometimes people forget. But if someone forgot to make sure the trans is in neutral before cranking the engine, do you think the odds of them remembering to make sure the trans is in neutral after starting the engine before releasing the clutch is any better? As many people as I have seen and heard of who pressed the clutch to start the engine and promptly released the clutch without realizing the trans is still in gear, I don't think so.

My other problem with that design is it is just plain inconvenient. Who wants to press the clutch every time they start the engine? I know it's not usually a big deal, but it's still an unnecessary inconvenience for IMO not much or any benefit. This is especially true when the passenger of the vehicle needs to start the engine for heat or AC when the driver isn't currently in the vehicle for whatever reason. I personally know several people who have had this problem at some point.

In my opinion, a better, more user friendly, and more effective method of preventing the vehicle from being started in gear would be for the manufacturers to implement a neutral safety switch like on automatic transmissions. That would virtually eliminate the possibility of the vehicle moving when started until the driver actually puts the trans in gear and releases the clutch rather than simply until they carelessly release the clutch as soon as the engine starts. This solution would also have the advantage of working with remote starts unlike the clutch safety switch, which is typically simply bypassed when a remote start is installed. Being able to start the engine from the passenger seat or without getting in the car would be a benefit too.

If anyone disagrees or has other thoughts, please let us know!
Another problem is the added wear on crankshaft thrust bearings when pressing on the clutch while starting.
 

Avery4

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Another problem is the added wear on crankshaft thrust bearings when pressing on the clutch while starting.
That's a great point! I thought I added that to my first post, but apparently I didn't. Without the engine running, there is no oil pressure to lubricate the thrust bearings. I'm not a fan of forcing unlubricated bearings to rotate under load, but that's just me.
 

Avery4

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And how are the thrust bearings lubricated after the engine runs, which oil pressure do they see?
With the engine running, pressurized oil is supplied directly to the thrust bearings via holes in the crankshaft to keep them lubricated. Without oil pressure to keep the surface of the thrust bearings separated from the crankshaft when under load (clutch pressed), the thrust bearings can experience unnecessary wear over time. This problem is made even worse when an aftermarket heavy duty clutch is installed due to the higher clamping pressure.
 

Avery4

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seems to me they reveive leaking oil from the main bearings
That could be, it has been almost a year since I have had a crankshaft out of an engine. But in any case, the fact that they receive no lubrication on startup other than whatever film of oil is left from whenever the engine was last run remains true.
 
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How about this then... do DCT engines suffer thrust bearing issues, or have different thrust bearings? On my car, one clutch is pushed to open like any other clutch, the other is pushed to close.

Hyundai uses 2 open clutches that are pushed closed electrically. The engine is constantly experiencing thrust when driving.

Seems that 1 second of not receiving oil during cranking isn't that big of a deal

Been years since I've seen thrust bearings worn to the point of causing issues. I have no idea what caused their demise but a betting man would put his money on skipped oil changes...
 
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