2019 Peterbilt 389 Transmission Fluid & Service

Quick answer

• Allison 4000 Series (Automatic):

  • OEM Fluid Spec: Allison TES 668™
  • Drain & Fill Capacity: Approximately 29-39 quarts (varies by pan depth and cooler size)
  • Full Overhaul Capacity: Approximately 44-59 quarts (varies by pan depth and cooler size)
  • Filter OEM Part Number: Internal filter kit P/N 29558114 (spin-on filter P/N 29548988, various others depending on configuration – verify with dealer or service manual)
  • Recommended Service Interval: 75,000 miles or 36 months (TES 668), or sooner for severe duty

• Eaton Fuller Advantage 10-Speed Automated Manual Transmission (AMT):

  • OEM Fluid Spec: Eaton PS-386 or equivalent synthetic 50W transmission fluid
  • Drain & Fill Capacity: Approximately 14-16 quarts
  • Full Overhaul Capacity: Approximately 17-19 quarts
  • Filter OEM Part Number: No external serviceable filter (internal screen only, not typically serviced)
  • Recommended Service Interval: Up to 500,000 miles or 5 years for highway applications; 250,000 miles or 3 years for vocational/severe duty

• Eaton Fuller RTLO-18918B 18-Speed Manual Transmission:

  • OEM Fluid Spec: Eaton PS-164 Rev 7 or equivalent synthetic 50W transmission fluid
  • Drain & Fill Capacity: Approximately 26-28 quarts
  • Full Overhaul Capacity: Approximately 28-30 quarts
  • Filter OEM Part Number: No external serviceable filter (internal screen only, not typically serviced)
  • Recommended Service Interval: Up to 500,000 miles or 5 years for highway applications; 250,000 miles or 3 years for vocational/severe duty

Fluid type explained

The 2019 Peterbilt 389 is a heavy-duty truck designed for a wide range of applications, and as such, it can be equipped with various transmissions. This significantly influences the type of transmission fluid required. Always verify the specific transmission model installed in your truck before purchasing fluid.

For Allison 4000 Series automatic transmissions, the critical specification is Allison TES 668™. This is Allison's latest generation fluid, designed to offer extended drain intervals, improved shear stability, and enhanced protection for the transmission's internal components. It's a fully synthetic fluid that outperforms older TES 295 fluids in nearly every metric. Using a TES 668™ approved fluid is paramount for maintaining warranty compliance and optimal transmission performance and longevity. Do not substitute with generic ATF or fluids not specifically approved by Allison.

For Eaton Fuller manual and automated manual transmissions (AMTs), such as the Advantage 10-speed AMT or an 18-speed manual like the RTLO-18918B, the fluid requirements are quite different. These transmissions typically specify a heavy-duty synthetic gear lubricant, often a 50W viscosity. Eaton has its own specifications, such as PS-386 for AMTs and PS-164 Rev 7 for manual transmissions. These specifications ensure the fluid provides the necessary film strength, thermal stability, and wear protection for the gears, bearings, and synchronizers (if applicable). Never use an automatic transmission fluid (ATF) in an Eaton Fuller manual or AMT, as it lacks the extreme pressure additives and viscosity required for these gearboxes.

Service procedure

The service procedure for your 2019 Peterbilt 389's transmission will depend heavily on whether it's an automatic or a manual/AMT transmission.

For Allison 4000 Series automatic transmissions, a drain and fill is the most common service procedure. This involves draining the fluid from the transmission pan and replacing the external spin-on filter (if equipped) and internal filter. A true