Manual transmission and parking

[Ben]

First off, please don’t even bother posting unless you truly understand what connects the crankshaft to the differential in a RWD, manual transmission car.

With that being said, when a car’s engine is shut off and in first gear while parked, what actually holds the car in place? Lets imagine that the parking break is not even being used. I’ve always just acknowledged the fact that leaving a car in gear with the engine off will hold it securely in place, but until now I have never really thought about what causes it to lock the drive wheels. I have always assumed that doing to puts stress on the transmission, but when I think about it I can’t understand what “locks” the transmission. The only thing I can think of is that the compression of the air in the cylinders restricts the crankshaft from turning, which in turn stops the transmission from turning, and ultimately stops the wheel from moving.

So what is it that actually holds a car in place? Again, don’t even bother posting if you’re just going to guess…odds are I could prove you wrong myself.

Topic

[EndSupremacy]

I can see by the number of posts you have (1) that you’re new to this site. That being said, you’re not going to get a lot of responses here with that attitude.

[cunno96]

i dont know is you have ever manualy turned a motor over but it does require a fair amount of force due to friction and a little bit to do with compression and most of the time cars are not parked on hills and when there on flat ground they are a little hard to push which is why when you have to push start a car you dont put it in to gear straight away (p.s. you can push start auto’s but it need to be over 30km an hour to work)

[Josh]

I think your right with the compression being the key factor. I personally have never done a compression start; but know how to do it. I was taught to always use the e-brake/parking brake (how ever you want to call it.) when parking the car to make sure its not going to start rolling away from you and you end up in a vary bad and sometimes embarrassing situation…My buddy when he had his 97 civic ex; surprised me when he never used the parking brake and just left it in say first gear when he parked it. Just actually thinking about this, I am wondering if not just the engine compression; but the gears inside the tranny have an effect on this; we all know that in order to get a manual car to go the engine has to be up at 1200 rpm to start moving the car, so the resistance of the gears in the tranny must play a role while parked.

[Byron Gudmestad]

Real Answer: Gravity
If you think compression or transmission holds your car in place, please park it on a 10 percent grade without a parking brake. Let us know how well that works out. Compression in the cylinders leaks out rather quickly, so don’t count on that. Low gear in your xmsn might slow it down, but don’t count on that either. Rolling resistance of the tires might make it hesitate before it heads south. Real Answer #2: Parking brakes hold your car in position, the rest are just obeying gravity.

Explain how parking with your transmission in gear is bad on it?? Just image what power from the engine would do to it.

[Josh]

if you have air leaking out of your cylinders you have a problem with compression. Either with your piston rings or with your cylinder head. Eric actually talks about this in a video he made about finding a dead cylinder. If you have any leaks at all it will not perform up to standard like the rest will.

[skim3544]

Like others said – the engine compression. And with clutch out, it is also connected to the transmission gear which has high torque (1st gear) Yes, it is not enough, but that is what you have to work with plus the parking brake. You don’t lock the transmission, you put it in the gear with high torque so it takes more energy to move the car. People who parks in city often put the gear in natural to minimize the towing damage.

[Josh]

Finally someone who agrees with me! I knew it had to be with the engine compression. But forgot about the torque figure.

[Phil Grimsey]

It’s quite possible to turn an engine over while in gear so I’d never bank on the motor alone holding a car still. It hardly takes an earth shattering effort to put a parking brake on now, does it?

[Josh]

engine compression, amount of torque moving the first gear, and the e-brake(parking brake) is what holds your car in place. And if your on a hill make sure your wheels are turned in the correct direction.

[Author]

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