2018 Jeep Cherokee Transmission & Axle Gear Ratios

Transmission gear ratios

The 2018 Jeep Cherokee was offered with two main transmission options: a 9-speed automatic and, in some export markets, a 6-speed manual (though the manual is very rare in North America).

ZF 9HP48 9-Speed Automatic (Front-Wheel Drive and All-Wheel Drive)

Available axle ratios

The axle ratio in your 2018 Jeep Cherokee plays a significant role in its performance, affecting everything from off-the-line acceleration to highway fuel economy. Available ratios varied depending on the engine, trim level, and whether the vehicle was equipped with two-wheel drive (FWD) or four-wheel drive (AWD/4WD).

Note: Specific RPO codes for axle ratios can sometimes be found on a build sheet or a sticker within the vehicle.

How to identify your axle ratio

Identifying your Jeep Cherokee's axle ratio is crucial for proper maintenance or modification. Here are the common methods:

• Door-Jamb RPO Sticker (FCA/GM style): For Chrysler/Jeep vehicles, look for a sticker on the driver's side door jamb or in the globe box. This sticker contains a list of three-digit "RPO" (Regular Production Option) codes. You'll need to cross-reference these codes with a decode list to find the specific axle ratio code. Common codes for axle ratios typically start with "D" (e.g., DEA, DEF, DEW). If you find the RPO codes, an online "VIN decoder" or a dealer can help you pinpoint the exact ratio.

• VIN Decoder: Many online VIN decoders can provide a detailed build sheet for your vehicle, which will include the axle ratio. Enter your VIN into a reputable decoder website.

• Dealer Service Department: A Jeep dealership can pull up your vehicle's build sheet using the VIN, which will explicitly list the original factory axle ratio.

Towing vs MPG impact

The axle ratio has a direct and significant impact on your vehicle's performance characteristics:

• Numerically Lower Ratio (e.g., 3.25): A numerically lower ratio means the engine doesn't have to rev as high to maintain a given road speed. This generally results in better fuel economy on the highway, as the engine operates at lower RPMs. However, it also means less mechanical advantage, which can lead to reduced towing capacity and slower acceleration.

• Numerically Higher Ratio (e.g., 3.73, 4.08): A numerically higher ratio provides more mechanical advantage, allowing the engine to put more torque to the wheels for every rotation. This translates to improved towing capacity, stronger acceleration, and better performance in off-road situations where low-speed torque is essential. The trade-off is often worse fuel economy, especially at highway speeds, as the engine will be revving higher.

For the 2018 Jeep Cherokee, if you plan on frequent towing or serious off-roading, the 3.73 or 4.08 ratios are generally preferred. If your primary concern is daily commuting and maximizing fuel efficiency, the 3.25 ratio is more suitable.

Common issues

While the 2018 Jeep Cherokee generally offers reliable driveline components, there are a few common areas where owners might experience issues related to the differentials and axles:

• Ring & Pinion Whine: A persistent whining noise from the front or rear of the vehicle, especially under acceleration or deceleration, can indicate wear or improper setup of the ring and pinion gears within the differential. This is often more noticeable with higher mileage or if the vehicle has been subjected to heavy towing or off-road abuse without proper fluid changes.

• Carrier Bearing Wear: The bearings that support the differential carrier can wear out over time, leading to humming or growling noises that change with vehicle speed. If caught early, replacing the bearings can prevent more extensive damage to the differential.

• Limited-Slip Clutch Wear (if equipped): Some Cherokee models, particularly those with advanced 4WD systems, may have a limited-slip differential. The clutches within these units can wear out, leading to a loss of limited-slip function, clunking noises during turns, or shuddering from the rear end. Regular fluid changes with the correct friction modifiers are crucial for these differentials.

Always address unusual noises or vibrations from the driveline promptly to prevent more costly repairs.

Find a driveline shop on Repairius.