What happens mechanically if you shift gears without depressing the clutch?

Question

I know it will damage the engine but how does it do so mechanically?

What effect would the occupiers of the vehicle, say a family sized car, experience?

Answer 1

All the stress and friction is applied directly to brass synchronizer rings when you shift without the clutch, The synchronizers are there to equalize the speed of the gears to prevent the gears from grinding. They are designed to work with the power disconnected from the transmission like when the clutch is disengaged. Shifting without the clutch does damage the transmission internal components and causes premature failure.

You can shift without using the clutch but you have to back off the throttle and shift slowly to keep from doing severe damage.
Speed shifting without the clutch will do damage.
If you want to shift fast, get an automatic with a shift kit installed.
There are very high end manual transmissions and air shifter set ups that use planetary gear sets. And then there's an ignition kill that helps shifting. The system kills the ignition for milliseconds so the the system can shift without the gears grinding.

The only way it might damage the engine is if you miss the gear and the engine over speeds.

If the transmission fails it can come apart taking the clutch and pressure plate with it, that can come through the floorboard on a rear wheel drive vehicle, On a front wheel drive vehicle it can break axles or the final drive causing the vehicle to spin uncontrollably or pull hard one direction or the other. This would be in the event of a catastrophic failure under extreme conditions like racing.

Answer 2

Well, you "know" wrong. Shifting without clutching will not damage the engine, heck, if you are an experienced driver and know the workings of a clutch, you can do it an not even damage the transmission, many people do.

On the back of your engine is a flywheel, bolted to the flywheel is a pressure plate. Between the flywheel and the pressure plate is the clutch disk, it turn with the flywheel because it is smashed real tight between the flywheel and pressure plate. The input shaft for the transmission attaches to the clutch disk.

When you press the clutch, the throw out bearing presses on the fingers of the pressure plate, causing it to pull away from the flywheel and let pressure off of the clutch disk. When this happens, the transmission is not being turned by the engine. You then slide the shifter into the next gear, and let off the clutch, thus allowing the engine to turn the transmission again.

It is possible to shift without the clutch, but you must be able to know your transmission well enough to feel when the RPM of the engine is right to slide it into gear and not cause gear clash.

In short, if YOU do this, it will grind gears in the transmission, and damage the transmission, not the engine.

Answer 3

If you do it properly?!? NOTHING. You just change gear.
If you do not know what you are doing everything might happen.

FROM:-

A loud noise without the gears changing.

TO:-
Finding the gear box on the floor.

It all depends on the nature of the gears.

Gears are wheels with teeth . When you change gear you are trying to release the drive gear(Engine side) from the driven gear (Wheels Side) and engage it to an other driven gear.

Depressing the clutch helps first of all to release the gears.
Second with the clutch down trough a little device called the synchroniser the teeth of the two gear try face the allows of the other gear so that they can engage without damage

When you change gear drive and driven will not go at the same speed any longer and when the try to engage they will try to wear each other.

A very expert driver can rearrange the speed of the drive gear by the accelerator and the speed of the driven gear with the brakes so that he can change without clutch.


P.S. Fangio never used the clutch wen he was racing.

Answer 4

If you are very very good you get a silent gear change. Otherwise you bring together parts if the gearbox moving at different speeds. This produces a naughty noise and can chip bits off the working parts in the transmission. Engine damage unlikely though

Answer 5

It won't damage the engine at all. In fact it's perfectly possible to change gear without the clutch if you're good enough at matching the engine revs to road speed. When done well, all the occupants of the car would notice, if they notice anything at all would be the speed of the geatchange.
If it crunches, you're doing it wrong and you are damaging the gearbox!

Answer 6

It is a long story.

The clutch disengages the connection between wheels and engine during gear change.

You move the gear lever, and disengage the gear in the gearbox (so that it is in neutral).

You continue to move it further, and the synchronisers (friction cone clutches) bite, and match the speed of your clutch disc (disengaged) to your selected gear.

Once the clutch disc is spinning at the "synchronised" speed, the blockers are released, and the gear lever can continue to move fully into gear, so that the new gear becomes engaged.

The clutch is then engaged, connecting the engine and wheels, using the new gear ratio.

Now, if this is done without disengaging the clutch, then the same effect has to be achieved, otherwise the new gear will not engage:-

to disengage the current gear, the engine must be trying to rotate at the same speed as the clutch (not trying to accelerate or deccelerate). Hence without any driving torque on the gear, it will disengage smoothly.

now to get into the next gear, the clutch must be made to spin at a speed "synchronised" with the wanted gear. If not then the synchronisers will be rubbing together at different speeds, and the blockers will prevent the gear from shifting.

the clutch can be made to spin at the right speed by adjustment of engine rpm. When the rpm across the synchroniser is zero (they are synchronised) the blockers will release, and the gear can be shifted.

It sounds complicated, and inside the gearbox it actually is. However you can change gear without the clutch quite easily (as long as you're changing up), by lifting your foot off the accelerator pedal as you're moving the gear lever out of gear. At the point where the engine is not transmitting driving torque, the gear will pop out, and you'll be in neutral. If you continue to move the gear lever (gently) into the next gear, it will not immediately go due to the synchronisers not being synchronised, and the blockers preventing engagement. If you keep light pressure on the gear lever to engage the next gear as the engine rpm falls firther, there will be an instant where the synchronisers will be synchronised and the gear will pop in. After that has happened you can accelerate again.

The only damage caused (assuming you're not forcing the lever too hard) is accelerated wear of the synchronisers.

I suppose it shouldn't be done, as failure of one of the synchronisers necessitates a complete gearbox strip down and re-build, plus the cost of the replacement parts. Not cheap.

Answer 7

If done properly, it will do no harm to the car and nobody in the car would even notice. You have to judge the revs on the engine and it will just slip into gear as normal. If it is done wrongly, you will strip the cogs off the gears. The occupants will hear horrible grating and grinding noises, and then they will have to push the car to the garage for a new gearbox.

Answer 8

Rally drivers etc do it all the time. If you let the throttle off before you clunk it into gear it'll be fine. I've ridden my bike all the way home with no clutch before now. Not recommended but it can be done. You're basically banging the selector through the gears while the drive is still turning them. If you gun the engine and do it, it'll go CRUNCHHH!!!

Answer 9

Depends, you can change gear without the clutch, but you need to match the engine speed with that of the next gear, older cars did not have clutches.....it is difficult to try and engage a gear when the engine revs and gearbox are not in Sync....it would damage to gear box rather than the engine, and the car would no doubt judder and a lot of squealing noises.

Answer 10

Won't damage the engine at all. In fact, if you match the engine rpms with the transmission shaft rpms, you don't need the clutch after first gear.