What Determines the Speed Difference Between 4.11 and 3.7 Axle Ratios in Tractors?
3 Answers
Tractor axle ratios of 4.11 and 3.7 are related to engine and transmission RPM. Here are the specifics: 1. Faster with 3.7 ratio: When the transmission is in overdrive and the engine runs at 1500 RPM, a 3.7 ratio vehicle can reach 105 km/h, while 4.11 only achieves 95 km/h. 2. Faster with 4.11 ratio: In direct drive transmission mode at 1500 RPM, a 3.7 ratio vehicle reaches 83 km/h, whereas 4.11 attains 74 km/h.
I've been driving heavy trucks for over 20 years and know the ins and outs of gear ratios. The difference between 4.11 and 3.7 comes down to the size ratio of the gears. A higher gear ratio is like using a smaller chainring on a bicycle to climb hills—the wheels turn slower but with more power. When hauling 30 tons in mountainous areas like Yunnan and Guizhou, a 4.11 ratio lets the engine work less hard while keeping the tires firmly planted. A lower ratio like 3.7 is like switching to a larger chainring on flat roads—the wheels spin faster at the same engine RPM, allowing you to cruise at 90 km/h with 500 fewer revs, saving fuel and reducing noise. But if you're hauling 40 tons uphill, it struggles—the engine screams and belches black smoke. Choosing the right ratio depends on load weight and typical road conditions: go for lower ratios on flat highways and higher ones for mountainous heavy loads. Pick wrong, and you'll be best friends with the gas station every day.
Veteran truck enthusiasts all know that the gear ratio is the proportion of engine power distributed to the wheels. A ratio of 4.11 means the crankshaft turns 4 times for every 1 wheel rotation, amplifying torque by over three times. A 3.7 ratio means the crankshaft turns 3.7 times per wheel rotation, offering less power but higher speed. High ratios ensure stable starts with heavy loads, effortlessly hauling ore up 40-degree slopes. Low ratios are ideal for high-speed cruising, reaching 90 mph at just 2500 RPM. However, engine displacement must match—small engines with high ratios are like an ox pulling a cart, while low ratios with small engines are like a skinny horse running on plains. Tire diameter also matters—385 wide tires pair best with high ratios. More transmission gears are better; a 12-speed transmission with a 3.7 ratio is most economical for logistics.
