In a BMW with manual transmission, the reverse gear is engaged by first pushing the gear lever down and then shifting it to the left and up. This is a safety feature to prevent accidental engagement of reverse gear while driving. Once the gear lever is in the correct position, the driver can release the clutch and apply the gas to move the vehicle in reverse. The reverse gear in a BMW with manual transmission operates similarly to other manual transmission vehicles, but the specific gear lever movement may vary slightly between different car models. **

In a BMW with manual transmission, the reverse gear is typically engaged by first bringing the vehicle to a complete stop. The driver then needs to push down on the gear lever and move it to the far left and up, usually past the first gear position, to engage reverse. This action is often accompanied by a distinct resistance or "lockout" mechanism to prevent accidental shifting into reverse while driving forward. Once in reverse, the driver can slowly release the clutch and apply gas to start moving the vehicle backward. **

Yes, it is possible to shift from a 5-speed manual transmission into 3rd gear. To do this, you would need to press the clutch pedal, move the gear shifter from its current position into the 3rd gear slot, and then release the clutch pedal smoothly to engage the gear. It is important to match the engine speed with the vehicle speed to ensure a smooth transition into the desired gear. **

No, it is not possible to shift directly from a 5-speed manual transmission to the 3rd gear. In a 5-speed manual transmission, you must shift sequentially through each gear, starting from 1st gear and working your way up to 3rd gear. Attempting to shift directly from 5th gear to 3rd gear can cause damage to the transmission and is not recommended. **

No, it is not possible to convert a 7-speed gear system to a 21-speed gear system. The number of speeds in a gear system is determined by the number of sprockets on the rear wheel and the number of chainrings on the front crankset. A 7-speed system has 7 sprockets on the rear wheel and one or two chainrings on the front crankset, while a 21-speed system has 7 sprockets on the rear wheel and 3 chainrings on the front crankset. Therefore, to convert a 7-speed system to a 21-speed system, you would need to replace the entire drivetrain, including the rear wheel, front crankset, shifters, and derailleurs. **

The speed of each gear in a vehicle depends on the specific gear ratios of the transmission. Generally, first gear has the lowest speed and highest torque, making it ideal for starting from a stop or climbing steep inclines. As you shift up through the gears, the speed increases while the torque decreases. The highest gear, typically fifth or sixth in a manual transmission, allows for the highest speed and lowest engine RPM, making it suitable for cruising at highway speeds. Automatic transmissions also have different gear ratios, but the specific speeds for each gear can vary depending on the make and model of the vehicle. **

As an AI, I do not have the ability to physically operate a vehicle, so I cannot accidentally shift from 5th gear to 4th gear in a BMW or any other car. However, if you are experiencing issues with shifting gears in your BMW, it may be best to have a professional mechanic inspect and diagnose the problem to ensure safe and proper operation of your vehicle. **

The main difference between an automatic car gear shift and a manual gear stick is the way they are operated. In an automatic car, the gear shift changes the gears automatically based on the vehicle's speed and engine RPM, without the need for the driver to manually shift gears. On the other hand, a manual gear stick requires the driver to manually engage and disengage gears by moving the stick and pressing the clutch pedal. This gives the driver more control over the vehicle's performance, but also requires more attention and coordination. **