Is it necessary to modify a manual transmission with overdrive gears?

[McMary]

The original factory configuration is best, and modification is not recommended. Here is an introduction to overdrive gear modification: 1. Modifying the transmission gear ratio: This refers to changing the number of gear teeth, usually done to save fuel. Typically, the fifth gear is modified. After modification, at the same speed, the engine runs at a lower RPM in fifth gear, saving fuel, and at the same engine RPM, the vehicle speed in fifth gear is faster. 2. Benefits: The top speed of the car can also increase. Overdrive gear modification is intended to break through the original fifth gear ratio limitation, achieving fuel savings and noise reduction in the most frequently used fifth gear at low RPM. The drawback is that there is a slight speed difference between fourth and fifth gears, and acceleration is slower than with the original gears at low speeds of 50-70 km/h. Whether this is acceptable depends on individual driving habits. Overdrive gear modification can harm the vehicle: 1. The engine and transmission gears are designed to be well-matched in terms of materials, manufacturing processes, and technical standards. 2. If modified to overdrive gears, the gear meshing and matching may not be as precise, potentially causing harm to the vehicle. Random modifications are not advised.

[Eddie]

I've been driving manual transmissions for over a decade, and last year I installed an overdrive gear set on my old Lavida. After the modification, highway driving became much more comfortable - at 120 km/h the RPM dropped from 3500 to around 2800, significantly reducing engine noise and improving fuel economy by about 0.5L/100km. However, city driving became less smooth, particularly the transition between 2nd and 3rd gears felt inconsistent, and there's noticeable torque deficiency when climbing hills. The modification might be worthwhile for frequent long-distance drivers, but it's crucial to find a reputable workshop as transmission modifications often lead to abnormal noises. Another consideration is the annual vehicle inspection - you'll need to keep the original gears as backup for inspection purposes.

[VanCassidy]

I opted for the overdrive gear mainly for cost-effectiveness, especially with fuel prices being so high these days. The material and machining cost me over 800 yuan, and the fuel savings from 20,000 km of highway driving have already covered that expense. However, there are a few key points to keep in mind: First, make sure your vehicle model has compatible gear kits available—my colleague's Focus couldn't find suitable parts. Second, pay attention to the transmission's load capacity, as older cars' gear strength might not keep up. Lastly, remember to visit the dealership for an ECU flash after the modification; otherwise, the ABS and speedometer will be inaccurate. Also, during every maintenance check, pay special attention to the transmission fluid condition.

[Arwen]

The key to overdrive gear modification lies in the usage scenario. I drive in the city 90% of the time, and after the modification, I deeply regretted it—the power delivery at low speeds became noticeably worse, requiring me to press the accelerator hard at every traffic light start. However, the improvement was obvious when driving on intercity highways, with reduced steering wheel vibrations after the RPM dropped. It's recommended for owners who frequently drive long distances, but for someone like me stuck on the ring road every day, it's really not worth the hassle. Modifying the gears also requires readjusting the clutch clearance, and if not done properly, the gearshift feel can become stiff. Now, I even need to apply some throttle when reversing to avoid stalling.