Differential & Rear Axle

Which gear ratio and which locker suit your rear axle when the tyres get bigger, or when the car needs better traction off-road or on track? Here you will find differential lockers, limited-slip differentials, ring and pinion sets, axle shafts, rebuild kits, housings and covers for you who want to upgrade or rebuild your differential.

What the differential components do

The differential distributes power from the propshaft to the wheels and lets them turn at different speeds in corners. The ring and pinion determine the gear ratio, the axle shafts carry the power out to the wheels, and the housing and cover keep the parts in place and the oil in. An open differential sends power to where resistance is lowest, so a wheel without grip can spin. A locker or a limited-slip differential can help with that.

How to choose a gear ratio

Bigger tyres make the overall gearing taller, so the car can feel sluggish. A ring and pinion set with a numerically higher ratio can restore pulling power, but typically gives higher revs at highway speeds. Choose based on:

• tyre diameter and the gearbox ratios
• the use: off-road, towing or highway
• axle type and size, e.g. Dana 44, which is stated in the product name
• that the front and rear axle on a 4x4 typically need the same ratio

Revolution Gear & Axle is available, for example, as gear packages in 4.10, 4.56 and 4.88, where the product name also states the bearings, e.g. Timken or Koyo. Some front axles require reverse cut gearing, so check the designation for the specific part number.

Locker or limited-slip differential

A differential locker locks the wheels on the axle together when you engage it and gives traction on both wheels off-road. ARB Air Locker is an example of a locker that is engaged with air. A limited-slip differential works automatically and distributes power more gradually, which can be an advantage on track and road. Cusco, Eaton and Wehrli are also brands in this category. Splines, axle type, bearing size and ratio range must match – ARB product names state, for example, 30 or 35 splines, and whether the locker fits 3.73 and lower or 3.91 and higher.

Installation and maintenance

Ring and pinion sets require correct setup of backlash, preload and contact pattern, so installation should be carried out by someone with experience and the right measuring equipment. An installation kit with bearings, shims and gaskets brings together the parts the job typically requires. Limited-slip differentials may require a specific oil or additive, depending on the product. If you hear whining or notice play, it can also be caused by worn wheel bearings and seals.

Frequently asked questions

What is the difference between a differential locker and a limited-slip differential?

A locker locks the wheels fully together when you engage it and is typically used off-road. A limited-slip differential works automatically and distributes power gradually, so the car can still turn smoothly in corners.

Does the speedometer need adjusting when the gear ratio is changed?

Often, yes. A changed gear ratio or tyre size can make the speedometer and odometer read incorrectly, and on some cars gear shifting is also affected. The solution depends on the car, and you should check what the change means for the vehicle inspection.

Why do new gears need to be run in?

The ring and pinion need to wear in together and can get very hot during the first miles. Follow the manufacturer's instructions, typically gentle driving without heavy towing, and change the oil once the break-in is complete.