2019 Jeep Wrangler Transmission & Axle Gear Ratios

Transmission gear ratios

The 2019 Jeep Wrangler (JL generation) offered a few transmission options, including a 6-speed manual and an 8-speed automatic. The gear ratios are crucial for understanding the vehicle's performance characteristics, from crawling off-road to highway cruising.

D478 6-Speed Manual Transmission

850RE 8-Speed Automatic Transmission (2.0L & 3.6L Engines)

Available axle ratios

The axle ratio plays a significant role in how your Wrangler performs, directly impacting acceleration, towing capability, and fuel efficiency. A numerically higher ratio (e.g., 4.10) provides more torque to the wheels, which is excellent for off-roading and towing, but will result in higher engine RPMs at highway speeds, thus decreasing fuel economy. Conversely, a numerically lower ratio (e.g., 3.45) will offer better fuel economy on the highway but less low-end torque.

Here are the common axle ratios available for the 2019 Jeep Wrangler:

How to identify your axle ratio

For a 2019 Jeep Wrangler, there are a few primary ways to determine your vehicle's axle ratio:

• Door-Jamb Sticker (RPO Codes): Check the sticker on the driver's side door jamb. Look for a three-digit RPO (Regular Production Option) code starting with "D." Common codes include "DSA" (3.45), "DMF" (3.73), and "DMH" (4.10).
• VIN Decoder: Many online VIN decoders can provide a build sheet for your specific vehicle, which will list the factory-installed axle ratio. You can usually find your VIN on the driver's side dashboard, visible through the windshield, or on the door jamb sticker.
• Axle Tag: While less common on newer vehicles, some older models or aftermarket axles might have a metal tag attached to one of the differential cover bolts, indicating the ratio. This is more prevalent in older Ford and Ram vehicles, but it's worth a quick check.
• Count Ring Gear Teeth (Last Resort): This is the most labor-intensive method. If all else fails, you can remove the differential cover and physically count the teeth on the ring gear and the pinion gear. Divide the number of ring gear teeth by the number of pinion gear teeth to get your axle ratio.

Towing vs MPG impact

The choice of axle ratio is a direct compromise between towing capability and fuel economy:

• Numerically Lower Ratios (e.g., 3.45): These ratios mean the engine turns fewer times for each rotation of the wheels. This results in lower engine RPMs at highway speeds, leading to better fuel economy. However, with less mechanical advantage, the vehicle will have less torque at the wheels, making it less suitable for heavy towing or extreme off-roading, especially with larger tires.

• Numerically Higher Ratios (e.g., 4.10): These ratios cause the engine to turn more times for each rotation of the wheels. This provides a greater mechanical advantage, delivering more torque to the wheels. This is ideal for towing heavier loads, crawling over obstacles off-road, and compensating for larger diameter tires. The trade-off is higher engine RPMs at highway speeds, which translates to decreased fuel economy.

For the 2019 Jeep Wrangler, if you plan to frequently tow or engage in serious off-roading, a 3.73 or 4.10 ratio is generally recommended. If your primary use is daily commuting and light off-roading, a 3.45 ratio will offer better efficiency.

Common issues

While the 2019 Jeep Wrangler is generally robust, specific issues related to its drivetrain components, particularly with heavily modified vehicles or those that see extreme use, can include:

• Ring and Pinion Whine: A common issue, especially with aftermarket gear sets or improper installation, is a noticeable whine coming from the differential, particularly at certain speeds or under load. This often indicates incorrect gear mesh or worn bearings.
• Carrier Bearing Wear: The bearings that support the differential carrier can wear out over time, leading to noise (growling or howling) and potentially excessive play in the differential.
• Limited-Slip Differential (LSD) Clutch Wear: If your Wrangler is equipped with a limited-slip differential, the clutch packs within it can wear out, leading to a loss of limited-slip function and sometimes shuddering or chattering during turns. Regular fluid changes with the correct friction modifier are essential for LSD longevity.

These issues are often exacerbated by aggressive driving, towing beyond rated capacities, or using oversized tires without re-gearing the axles.

Find a driveline shop on Repairius.