What size rear axle is a 4.875 ratio?
2 Answers
4.875 ratio refers to the 153 rear axle. Below is relevant information about gear ratios: 1. Introduction: The automotive transmission ratio, also known as gear ratio, refers to the speed ratio between two transmission mechanisms before and after the gearbox in a vehicle's drivetrain. There are two types of gear ratios in automotive transmission systems: the final drive ratio and the transmission gear ratio. For the same vehicle model, the final drive ratio is a fixed value, and gear ratio data for various vehicle types can be found in automotive performance manuals. 2. Comparison: Different gears in the transmission have different ratios, and different vehicles also have varying final drive gear ratios in their differentials. A larger ratio means slower speed but greater torque, while a smaller ratio results in higher speed but reduced torque.
I've been running into this issue frequently while modifying my truck. The 4.875 ratio isn't actually the physical size of the rear axle - it refers to the gear ratio, meaning the input shaft rotates once while the output wheels turn 4.875 times. This high ratio is ideal for vehicles needing strong low-end torque, like off-roaders or heavy-hauling trucks, especially useful when climbing hills. Rear axle sizes are typically measured in inches or by model numbers, such as the common Ford 8.8-inch or Dana 60 housings. If you're matching a 4.875 ratio, you'll likely need a larger axle housing to ensure structural integrity and prevent overheating or damage. I learned this the hard way during my upgrade - small housings with high ratios can fry your gears, so I recommend checking your vehicle manual or measuring the housing first. Generally, 4.875 ratios are popular for towing applications, but remember they'll increase fuel consumption while delivering noticeably quicker acceleration when passing.
