Hot answers tagged

53

Most of the time when you drive, you're putting a load (and causing wear) on what I'm going to call the "forward" face of each tooth on each gear in your drivetrain. The front of a tooth on the crankshaft pushes against the back of a tooth on the next gear in line, which pushes the next gear, etc. When you use "engine braking", all you are doing is ...


38

In manual transmissions, the reverse gears use a different type of gear teeth than forward gears. Forward gears are helical gears, which have teeth that are pointed at an angle. When the gears rotate, most of the load is evenly spread due to the angles. Reverse gears are cut into spurs, which don't absorb the load quite so well. As a result, there is ...


34

This is one of those things which are easier said than done. To start with, let me show you a picture of a four speed transmission which has been blown apart: All of those hundreds of parts go through the front end of the transmission. If a single part is bad (which it usually is not the case), you have to pull all of this apart in order to diagnose and ...


22

Most of the time you won't need heavy braking in traffic. You can avoid stopping and starting by: Driving more calmly Leaving plenty of distance between you and the vehicle in front (even at low speed) Simply taking your foot of the accelerator early If you let the car slow down, and use the gear until it is no longer appropriate (too slow that the ...


21

Two of the useful features of this setup (I have no evidence to prove they were the design reasons) are: when braking in a hurry stamping down until you reach the bottom will leave you in first, NOT neutral. This is much safer in many respects than being left with no power in an emergency situation. when starting from neutral, there is no risk of ending up ...


20

tl;dr: different gear ratios are a feature, not a bug. Some cars use more gears for acceleration, some use them for better gas mileage. You can't do both. At 3300-3500 RPMs, shouldn't the WRX be able to achieve better gas mileage by keeping the same 5-speed gear ratios, while adding an additional gear to lower RPMs to 2800-3000? You've exposed the ...


18

If you downshift into a gear at a RPM that is within the norm of driving then no, no harm done. When you downshift what is slowing you down is actually the compression stroke and is recommended over hard braking. Like another said, it is a bit of a mix of the two but engine braking is ok as long as the engine stays under redline, so do not go from 5th to ...


15

It sounds like the clutch is worn out... You can usually tell by gradually applying the gas in the top gear, probably around 2,500 RPM, and the car should accelerate a little bit, but at some point as you press the gas further and further down, you will feel it release and the revolutions will shoot way up without road speed increasing. It basically feels ...


15

For general driving, you can leave the car in drive. It doesn't damage the transmission leaving it in drive while stationary at the lights - although you don't want to be doing silly things like revving the engine while holding the brakes on. In an automatic car, you don't really use neutral. It is a step on the way to selecting Park, which means that the ...


15

To my understanding, no. I've never seen this behavior before in any auto I've ever driven or read about. I think it would be a safety issue if it did. If you needed to move suddenly (for whatever reason), pulled your foot off the brake pedal expecting the car to move, and it does nothing but rev the engine at you. This could be extremely dangerous on an ...


14

It's definitely not great. The redline is there for a reason. That shaking was likely the engine speed limiter looking at the RPMs and saying, "yes, that's high enough." The speed limiter can be either an ignition cutoff or a fuel cutoff - both will make the car feel very shaky. The most common bad consequence of an overspeed condition when the engine ...


13

Which would you rather change - your brake pads or your clutch? By downshifting to decelerate you are trading wear on your brake pads for wear on your clutch (among other things). Brake pads are much cheaper and easier to replace than a clutch. Personally, having done both, I'd rather do 50 brake jobs before I'd do one clutch job.


13

tl,dr: The short answer is no, with caveats. The longer answer starts with "well, you can kill your car with anything if you try hard enough." Let's use specific examples of when you should use your transmission for engine braking: Waimea Canyon or Mount Washington. In either case, you are descending thousands of vertical feet at significant grades. If ...


13

Answer The technical reason that manufacturers have chosen to use a sequential shift pattern with their gearbox configurations is that a standard shift plate that allows the selection of any gear desired is too bulky to fit into modern motorcycles. The REAL REASON this configuration is used is that it's defined in the US Code of Federal regulations under ...


12

It's not something I've ever attempted, but I know people who have... The innards involve a lot of small springs, shims, etc (mainly in the synchros), and these can often have a habit of flying off when released! It is something that should only be attempted in a decent, clean workshop/garage so you can keep track of all the bits as you take it apart, and ...


11

Donovan's is the only answer that has any truth in it. Downshifting and engine braking will have NO effect on the clutch, as you don't slip the clutch it doesn't wear out the engine, as you use the compression stroke and it is far better on tyres and handling as any advanced driving instructor would tell you. It is just more difficult, as you need to ...


11

It is straightforward to do this without any wear to your synchromesh, but it takes a lot of practice, especially when downshifting as you need to match revs accurately. Learning to heel and toe correctly will help you a lot here! You should never need to race the engine, as you should be using the same rev range as you would normally driving the car!


11

The main purpose of neutral on an automatic is for towing or pushing the car. Obviously you can't push it with the transmission in park, and if you tow it with the transmission in gear or in park and the drive wheels are in contact with the ground, you'll ruin your transmission or your tires or both. I'm sure there are some other uses too, but they're ...


11

Newtons Third Law For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The lateral center of gravity (CG) is above the axle as well. So you have ...


10

I have heard that most modern cars have rev limiters which prevent damage - is this just to prevent damage to the engine, transmission or both? The rev limiter is there to protect the engine, often to prevent problems caused by the transmission (or the human operator's use thereof). Would that help in this situation? Yes, it would but no, it ...


10

They will probably work out to be the same. An automatic transmission is inherently more complicated which means more can go wrong and usually does (more so than manuals). The increased complexity also makes them more expensive, heavier, less fuel efficient etc. A manual transmission is less complicated which means there is less that can go wrong. Through ...


10

Gearbox designers should avoid integer ratios like the plague. For mechanical reasons. Integer ratios will accelerate wear and tear because it increases the frequency with which tooth A on the driver gear will meet tooth B on the driven gear. This frequency is known as the hunting tooth frequency, which I've explained in more detail here. Regarding 1:1 ...


10

The somewhat longer answer is that the device that makes what you're asking possible is the torque converter. This device is a pair of curved blades setup as an impeller, and a turbine. The following cutaway pictures illustrate this setup: Here is a torque converter split in half for a better view: The way this works is explained really well by a ...


10

The difference comes down to the driver. While automatic racing gearboxes can beat a driver when it comes to performance, for the type of vehicle you describe, a manual can perform significantly higher than an automatic if the driver knows how to use it. But then if you really wanted high acceleration you would choose a different car. Maintenance is much ...


9

If you match revs correctly you should be able to change gear with no ill effects at all. The challenge is of course to match revs. This is pretty easy when accelerating, but when decelerating you'll need to use the accelerator to bump the engine revs up to match. Google for heel-and-toe (this also helps make for faster downshifts when using the clutch) ...


9

You'll find the following will all affect your speed and acceleration: wind speed - a head wind will slow you down more than you would think your clothing - this directly impacts drag bike configuration - you'll go slower with panniers on than with them off weight - a full tank will mean you accelerate more slowly temperature - cooler air can give you a ...


9

Your questions don't appear to match the headline, but to try and help: Why are gears used when there is automatic gear technology? Because automatic gears have more losses- so you don't get as much efficiency from your drive train. Because automatic gears can't read your mind and may not choose the best gear for what you want to do. Because the ...


9

It sounds like they're trying to take you for a ride to me. I can't see how driving style could cause the slave cylinder to fail - they're separated by a mechanical linkage. I would also dispute that anyone could destroy a clutch with 32k of normal driving - I'd expect it to last at least twice that long. However, a leaking cylinder might cause ...


9

If the RPM rises without a corresponding change in velocity in a vehicle with a manual transmission you've got a slipping clutch.


9

It depends on the type of hybrid car you are talking about. In one type of hybrid, there will be a gasoline engine and at least one electric engine capable of driving the wheels. In this case, the gasoline engine must still use a transmission because it cannot be revved too high without causing major damage or shortened life. One possible solution to this ...



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