2018 Peterbilt 579 Transmission Fluid & Service Spec

Quick Answer

• Transmission Make/Model: Eaton Fuller Advantage Automated (various models, typically 10-speed or 13-speed AMT)
• OEM Fluid Spec: Eaton PS-386
• Drain & Fill Capacity: Varies significantly by transmission model. Typically 12-16 quarts for 10-speed, 14-18 quarts for 13-speed. Always verify with your service manual.
• Full Overhaul Capacity: Varies. Approximately 16-20 quarts for 10-speed, 18-22 quarts for 13-speed. Always verify with your service manual.
• Filter OEM Part Number: Verify with your dealer or service manual as filter requirements can vary by specific transmission model and production date.
• Recommended Service Interval:
  • Normal Duty: 250,000 miles or 30 months
  • Severe Duty/Towing: 125,000 miles or 18 months

Fluid Type Explained

The 2018 Peterbilt 579, especially if equipped with an Eaton Fuller Advantage Automated Manual Transmission (AMT), requires a specific transmission fluid known as Eaton PS-386. This is a synthetic or semi-synthetic lubricant engineered to meet the demanding requirements of heavy-duty truck transmissions. It offers superior thermal stability, oxidation resistance, and excellent anti-wear properties, which are crucial for the longevity and efficient operation of these complex transmissions.

Using a fluid that does not meet the Eaton PS-386 specification can lead to a number of problems, including premature wear of internal components, poor shifting performance, increased operating temperatures, and ultimately, transmission failure. Always consult your owner's manual or speak with a Peterbilt dealer to ensure you are using the correct fluid for your specific transmission model.

Service Procedure

For Eaton Fuller Advantage AMTs, the most common service procedure is a drain and fill. A full flush or exchange is generally not recommended unless there has been a major component failure or contamination incident requiring a complete overhaul.

Drain & Fill Procedure (General Guidelines - Always consult your service manual):

1. Preparation: Ensure the truck is on level ground and the transmission is at operating temperature. Gather all necessary tools, new fluid, a suitable drain pan, and safety equipment.
2. Drain Fluid: Locate the drain plug on the transmission pan. Place the drain pan underneath and carefully remove the drain plug. Allow all the old fluid to drain completely.
3. Replace Filter (if applicable): Some Eaton Fuller transmissions may have an inline filter or a pan filter. If your model has one, replace it according to the manufacturer's instructions. Verify with your service manual.
4. Reinstall Drain Plug: Once all fluid has drained, clean the drain plug and surrounding area. Reinstall the drain plug, ensuring it's tightened to the manufacturer's specified torque.
5. Refill Fluid: Locate the fill plug. Using a fluid pump, begin adding the new Eaton PS-386 fluid. Fill until the fluid level reaches the bottom of the fill hole. Start the engine, run through the gears to circulate the fluid, and recheck the level. Top off as necessary. Do not overfill.

Important Note: Always refer to your Peterbilt 579's specific service manual for the exact procedure, torque specifications, and fluid capacities for your transmission model.

Service Interval

The service interval for your 2018 Peterbilt 579 transmission is highly dependent on its operating conditions:

• Normal Duty: For vehicles operating under typical highway conditions, without consistently heavy loads or extreme temperature variations, a service interval of 250,000 miles or 30 months is generally recommended.
• Severe Duty/Towing: If your Peterbilt 579 is frequently used for heavy hauling, operates in stop-and-go traffic, experiences extreme temperatures (very hot or very cold), or involves significant off-road usage, the service interval should be shortened to 125,000 miles or 18 months. These conditions place greater stress on the transmission fluid, causing it to degrade more quickly.

Adhering to these service intervals is crucial for maximizing the life of your transmission and preventing costly repairs.

Common Transmission Problems

While Eaton Fuller Advantage AMTs are generally robust, certain issues can arise in this generation of transmissions:

• Sensor Failures: Speed sensors, temperature sensors, or shift fork position sensors can occasionally fail, leading to diagnostic trouble codes, erratic shifting, or even a loss of drive.
• Clutch Wear Issues: Even with automated manual transmissions, the clutch is a wear item. Premature wear can occur due to aggressive driving, heavy loads, or improper clutch calibration, leading to slipping, delayed engagement, or difficulty shifting.
• Actuator Problems: The electronic actuators responsible for shifting gears can sometimes experience malfunctions, resulting in missed shifts, grinding noises, or the transmission getting stuck in a particular gear.
• Fluid Degradation: As noted, neglecting fluid service intervals or using incorrect fluid can lead to overheating, component wear, and eventual transmission failure. Oxidized or contaminated fluid loses its lubricating properties, causing increased friction and heat.
• Wiring Harness Issues: Given the complex electronic controls of AMTs, damaged or corroded wiring harnesses can interrupt communication between the transmission control module and various components, leading to a wide range of shifting problems.

Regular maintenance, including proper fluid changes, and prompt attention to any warning lights or unusual shifting behavior, can help mitigate these common problems.

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