What is the 4th gear in a car?
3 Answers
Car 4th gear is a relatively fast gear, corresponding to a speed range of 40-60km/h. The following introduces the matching speed for each gear and the timing for upshifting: Matching speed for each gear: First gear is for starting, with a speed generally between 0-5km/h. Second gear corresponds to 5-20km/h, third gear to 20-40km/h, fourth gear to 40-60km/h, and fifth gear to 60-100km/h. The 6th gear is for speeds between 100 to 120 kilometers per hour. Timing for upshifting: When the engine has ample power, it emits a dull "humming" sound. After upshifting, if there is no power deficiency or shaking of the transmission mechanism, and the speed increases quickly with the vehicle running very smoothly and naturally, it indicates the upshifting timing is accurate.
I think many people are curious about what the fourth gear is for when they first encounter it. In my years of driving manual transmission cars, the fourth gear has been a super commonly used gear, especially for long-distance driving on highways. It doesn't have the power of lower gears, nor is it as fuel-efficient as higher gears, but it maintains a steady speed, keeps the car from being too noisy, and reduces engine sound significantly. In the city, I rarely use the fourth gear because the third gear is more suitable for starting and slow speeds. But once on the highway, shifting to the fourth gear feels particularly smooth, maintaining a stable speed of around 60-70 mph, with decent fuel consumption control. I remember one time driving from the city to another location, using the fourth gear the whole way, and the engine showed almost no stress. Upon returning, the inspection revealed minimal wear. Of course, modern automatic transmission cars also have a D4 mode, which serves a similar purpose—limiting the transmission to the first four gears. It's especially useful for steep climbs or towing, preventing the car from shifting gears unnecessarily. With more driving experience, you'll realize that using the fourth gear properly can protect the engine and save a lot on fuel costs.
To talk about the fourth gear, let me briefly explain from a mechanical perspective. In a manual transmission, the fourth gear is designed with a 1:1 gear ratio, meaning the engine output matches the tire rotation speed, making it the smoothest to drive, and it's typically used at speeds above 50 or 60 km/h. In automatic cars, the D4 option follows a similar principle, preventing the transmission from shifting to fifth gear or higher to avoid frequent gear changes and component wear. When driving, I find the fourth gear most suitable for medium-speed cruising, whether on city ring roads or rural roads, as the engine load is moderate—not as fuel-consuming as third gear or as sluggish as fifth gear. Personally, when driving an automatic car in rainy or slippery conditions, I shift the gear lever to D4 to maintain stable speed and reduce the risk of skidding, making it much safer. Compared to other gears, the fourth gear has a 'middle-of-the-road' feel: not the fastest or most powerful, but when used correctly, it saves fuel and extends the lifespan. For daily maintenance, I also recommend using the fourth gear more often and avoiding relying too much on higher gears for acceleration, as this helps prevent transmission issues.
