Fewer and fewer car manufacturers are making new cars with manual transmissions these days, which is a real shame. Learning to drive a manual transmission-equipped car gives the driver an understanding of how gear changes impact the way a car moves. Another significant benefit of manual transmission cars is that you can start them fairly easily even when the battery is dead or the starter is not working. This technique is called “push-starting” or “bump-starting”. Knowing how to push-start a manual transmission car is a skill that can get you temporarily out of a jam and back on the road in no time. It is simple to do and totally safe if you do it right. To help you start your car the next time your battery dies out on you, here’s how push-starting works and how to do it right and safely, without damaging your car or truck.
How a Manual Transmission Works | The Basics
A manual transmission works just like the gears on a mountain bike. The shift stick moves a selector between different gears allowing to select different gear ratios. When a manual transmission is in neutral, the gears are not engaged and the car or truck can be rolled by hand. However, when in gear, a manual transmission car is difficult to push. Unlike an automatic car that must be in neutral or park to start, a manual transmission can be started while engaged in any gear, as long as the clutch is depressed.
When the clutch pedal is depressed, the transmission is also on neutral, even if the shift stick is in gear. When the clutch is released, it engages the engine with the transmission.
You have probably heard of gear ratios before but the topic can be very confusing. A gear ratio refers to the number of turns a gear rotates for each turn of the driving gear. So, a gear that has a ratio of 3:1 will rotate three times each time the driving gear turns once.
A manual transmission will always have numerically higher gear ratios in the lower gears. A typical three- or four-speed manual transmission will have a final gear close to 1:1, while the first gear may be 3:1.
A transmission must shift from one gear to the next because numerically higher gear ratios run out of power quickly. By shifting your transmission into a numerically lower gear, you can keep accelerating.
Tall gear is a confusing term. When referring to a transmission with low numerical ratios, the gears are called “tall.” The term comes from the need to drive in that gear up to higher RPM points before shifting. In contrast, a “low” gear ratio is numerically higher and must be shifted faster, albeit with a lower final top speed.
A wide-ratio manual transmission uses gear sets with a large differential in the numerical value of the ratio. This means that when the transmission shifts from a low gear to a higher gear, the RPM of the engine will drop more. Narrow-ratio manual transmission cars shift quicker than wide-ratio transmissions. You will find wide ratios in trucks and heavy vehicles, while narrow transmission ratios will be in lighter, sportier cars.
Granny gears are much less common today than in decades past. A granny gear is a particularly high gear ratio in first gear. The purpose of a granny gear is to enable large, heavy vehicles to start moving without stalling. When you shift a truck with a granny gear, you usually start in second unless under a load. First gear is only useful for getting the truck moving, then you must shift into second to continue accelerating. This is why big rigs often take so long to accelerate from a stop.
An overdrive manual transmission features a final gear ratio of less than 1:1. This means the drive gear turns less than once per rotation. An overdrive allows an engine to operate at a lower RPM and a higher top speed to conserve fuel.
What is Push-Starting and How Does it Work?
The theory behind push-starting is simple. For an engine to start, it must be rotating. Usually, the starter turns the engine by engaging with a gear at the back of the engine. This gear is called a ring gear and in a manual transmission, it is welded to the flywheel. The flywheel is the surface the clutch engages the engine with. When the starter fails, the ignition key won’t start the car anymore. When it happens, if you drive an automatic car, you will probably have to get a tow, but if you drive a manual transmission car, you’ll still be able to start it, even when any of these components fail.
Push-starting is a method used to force the engine to turn using the rotation of the drive tires. The engine, once rotating fast enough, will fire up by itself.
When done correctly, this is a totally safe way to start a manual transmission car. This trick will work when the battery is dead, or any starting system component is failing.
However, the same is not true for every charging system component. If the alternator is not working, for example, you may be able to start the car nut it will probably die out right after that. Cars simply can’t run without a constant supply of electricity coming from the alternator.
Before you try and push-start a car, you need to make sure you can do it safely. This means having plenty of room to move your car. A helping hand is useful and might be essential if your car or truck is quite heavy. It’s also important to remember that you will not have power steering or power brakes until the car starts, so planning ahead is essential.
Steps for Push-Starting a Manual Transmission Vehicle
Step One: Getting Ready
The first step you need to take is to have the key in the ON position. When the key is in this position, electricity is available to the various components essential for starting a car. The car will not start if the key is not in the ON position. When the key is on the OFF or ACC position, no power is sent to the fuel or ignition system.
Step Two: Positioning Your Car
You will need a good amount of open road ahead of you. Make sure there’s no cross-traffic, obstacles, or anything else that might come in your way. Once you’ve started pushing the car, it might be quite hard to stop, especially without the help of a brake booster. Parking lots are good places to push-start a car. With practice, you should be able to push-start your car in as little as 15 feet but if it’s your first time, you’re better playing it safe. Give yourself more room than you think you’ll need it whenever possible.
The second step is to identify where you are going to roll the car or truck. Avoid uphill roads, speed bumps, and driveways when possible.
Step Three: Push-Starting a Manual Transmission
The third step is easier when you have help. You will want to place the transmission shifter in neutral, then roll the car forward. You will need to get the car going to about 5 mph, about the speed of a good walk. The next part takes timing and practice, so if you don’t succeed the first time, try again.
With your car rolling at 5 mph or more, jump in and depress the clutch, move the shifter into second gear, and release the clutch. You do not want to ease the clutch out like you normally would because you want sudden rotation of the engine. If you do this step correctly, the engine will start.
Once the engine starts, depress the clutch before the engine stalls.
Why Start in Second Gear?
You should use second gear when possible because of gear ratios, as we describe above. In first gear, you’ll need to push the vehicle a lot faster for the engine to start without stalling. Push-starting a car in second gear is simply easier as it required a lower speed to cause the engine to turn.
What About Hills?
A dead battery or a weak starter can happen anywhere at any time. If your manual transmission car won’t start and you are parked on a hill, you can push-start it, but it takes a little more planning. First, if you are facing uphill and can’t turn the car around, push-starting is going to be a lot more challenging.
In this instance, you will have to use the reverse. Reverse gears are numerically higher than first gear ratios. That means when the car starts, it’s going to want to take off. You will need to be ready to apply the brakes and engage the clutch to prevent rolling to the bottom of the hill and potentially hitting something.
If you are facing downhill, well, lucky you! Just give the car a little push, jump in, wait for the car to gain some speed, and drop the clutch in second gear.
Push-starting a car is a skill you should learn to execute, preferably before you actually need to do it for real. Knowing how to push-start a car will make sure you can get home even if your starter or battery is not working. You can always practice push-starting your car with the help of a friend in an empty parking lot. With some practice, you’ll probably even be able to start it by yourself!