2015 Jeep Grand Cherokee — Transmission & Axle Gear Ratios

Whether you are upgrading your drivetrain for larger tires, calculating towing capacities, or rebuilding a damaged differential, knowing the exact gear specifications of your 2015 Jeep Grand Cherokee (WK2 generation) is essential. The 2015 Grand Cherokee relies exclusively on advanced 8-speed automatic transmissions paired with specific axle ratios tailored to its diverse engine lineup—from the efficient 3.6L Pentastar V6 to the robust 3.0L EcoDiesel and the aggressive 6.4L SRT Hemi.

Below is a comprehensive guide to the internal transmission gear ratios, available axle ratios, and driveline specifications for the 2015 Jeep Grand Cherokee.

Transmission gear ratios

For the 2015 model year, Jeep equipped all Grand Cherokees with an 8-speed automatic transmission. The 3.6L V6 uses the Chrysler-built 845RE, while the 5.7L V8, 3.0L EcoDiesel, and 6.4L V8 use the heavier-duty ZF 8HP70. Despite the differences in torque capacity and internal component strength, both transmissions share the same optimal internal gear ratios.

8-Speed Automatic (845RE & 8HP70)

These closely spaced ratios provide aggressive low-end torque multiplication for off-road crawling and towing, while the double-overdrive 7th and 8th gears significantly reduce engine RPM at highway speeds for enhanced fuel economy.

Available axle ratios

Jeep simplified the axle ratio offerings for the 2015 Grand Cherokee compared to older generations. The ratio you have depends almost entirely on the engine your vehicle is equipped with.

Note: The 5.7L V8 and 3.0L EcoDiesel utilize a numerically lower 3.09 ratio because they generate significantly more low-end torque than the V6, allowing them to pull heavy loads efficiently without needing a higher gear ratio.

How to identify your axle ratio

If you are unsure which axle ratio your 2015 Jeep Grand Cherokee has, there are a few straightforward ways to confirm your specific setup:

• VIN Decoder / Build Sheet: The most reliable way for modern Chrysler/Jeep/Dodge vehicles is to run your Vehicle Identification Number (VIN) through an FCA build sheet generator or a reliable VIN decoder. This will list the exact sales code (e.g., DLR for 3.45) your Jeep was built with.
• The Axle Tag: Crawl under the rear of the vehicle and look at the differential cover. Factory axles usually feature a metal tag bolted to one of the differential cover bolts or a white sticker on the axle tube. This tag will explicitly state the ratio (e.g., "3.45" or "3.09").
• Door-Jamb RPO Sticker: While GM vehicles prominently feature an RPO code sticker in the glovebox or door jamb, FCA vehicles typically have a basic compliance sticker in the door jamb. However, checking this sticker can provide your gross axle weight ratings, which can help narrow down your towing package.

Towing vs MPG impact

The relationship between your axle ratio, fuel economy, and towing capability is a classic automotive trade-off.

• Numerically Lower Ratios (e.g., 3.09): Often referred to as "taller" gears, lower numbers mean the driveshaft turns fewer times for every rotation of the wheels. This setup keeps engine RPMs lower at highway speeds, which significantly improves fuel economy (MPG). The downside is less mechanical torque multiplication off the line. For the V8 and EcoDiesel, their massive engine torque makes up for the taller gear.
• Numerically Higher Ratios (e.g., 3.70): Known as "shorter" gears, a higher number means the engine and driveshaft spin faster at any given speed. This provides more wheel torque, making it much easier to accelerate rapidly or get heavy trailers moving from a dead stop. The trade-off is higher highway RPMs, which can negatively impact your fuel economy.

Common issues

While the WK2 Grand Cherokee's driveline is generally robust, high-mileage or heavily abused models can experience a few common differential and driveline issues:

• Ring & Pinion Whine: A high-pitched whining noise under acceleration or deceleration often indicates improper gear mesh or excessive wear on the ring and pinion gears. This can happen if the differential fluid is neglected or after severe towing.
• Carrier Bearing Wear: A low-pitched rumble or growl that increases with vehicle speed can point to worn carrier bearings or pinion bearings inside the differential housing.
• Electronic Limited-Slip Differential (ELSD) Clutch Wear: Models equipped with the Quadra-Drive II 4x4 system feature an ELSD in the rear. Over time, the internal clutch packs can wear out or the actuator motor can fail, leading to a "binding" sensation around tight corners, shuddering, or a "4WD System Service" message on the dash. Regular fluid changes with the correct friction modifier are critical.

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