2015 Peterbilt 579: Transmission Fluid & Service

Quick answer

• Transmission make/model: Eaton Fuller FR-15210B (10-speed manual), Eaton Fuller FRO-16210C (10-speed manual), Eaton UltraShift PLUS (automated manual), or Allison TC-10 (automatic).
• OEM fluid spec: Eaton Fuller transmissions require PS-386 (formerly PS-164 rev 7) compliant synthetic fluid. Allison TC-10 transmissions require TES-668 or TES-295 compliant synthetic fluid.
• Drain & fill capacity: Approximately 7.5 quarts (7.1 liters) for Eaton Fuller models. Approximately 38 quarts (36 liters) for the Allison TC-10.
• Full overhaul capacity: Approximately 16 quarts (15.1 liters) for Eaton Fuller models. Approximately 47 quarts (44.5 liters) for the Allison TC-10.
• Filter OEM part number: For Allison TC-10 models, use kit part number 29558329. For Eaton Fuller models, an external filter/cooler system may be present; verify with your dealer or service manual.
• Recommended service interval: For Eaton Fuller models, 500,000 miles (800,000 km) for linehaul applications. For Allison TC-10 models, 150,000 miles (240,000 km) for normal duty, or 100,000 miles (160,000 km) for severe duty.

Fluid type explained

The 2015 Peterbilt 579 could be equipped with several different transmissions, the most common being the Eaton Fuller manual and automated manual transmissions, and the Allison TC-10 automatic. It is critical to use the correct fluid, as these transmissions have very different requirements.

For the widely used Eaton Fuller transmissions, such as the FR-15210B and FRO-16210C, a high-performance synthetic fluid meeting the PS-386 specification is required. This fluid is designed to provide exceptional thermal stability, shear resistance, and lubrication over long service intervals, protecting gears and bearings from wear under the immense torque of a Class 8 truck.

For the Allison TC-10, a fully automatic transmission with a twin-countershaft design, a synthetic fluid meeting Allison's TES-668 or the earlier TES-295 specification is mandatory. These fluids are engineered to maintain their viscosity and protective qualities under the high-heat conditions generated by the torque converter and clutches. Using a non-compliant fluid can lead to overheating, poor shift quality, and premature transmission failure.

Service procedure

A transmission service on a Peterbilt 579 typically involves one of two procedures: a drain and fill, or a full fluid exchange. A drain and fill is the most common service. It involves draining the fluid from the transmission pan, replacing the filter (on Allison models), and refilling with fresh fluid. This process removes most, but not all, of the old fluid.

A full fluid exchange, often done with a specialized machine, replaces nearly all of the old fluid by simultaneously pumping out the old fluid while pumping in new fluid. This is a more thorough service but is also more expensive and time-consuming.

For the Allison TC-10, replacing the external filter is a crucial part of the service. For Eaton Fuller transmissions, there is no internal filter to change; however, some trucks may be equipped with an external cooler and filter assembly that will need to be serviced as well. Always verify the presence of an external filter.

Service interval

The recommended service interval depends heavily on the transmission model and the type of service the truck is used for.

For Eaton Fuller transmissions in a standard linehaul application, the recommended fluid change interval is a lengthy 500,000 miles (800,000 km). However, for severe-duty applications, such as vocational or heavy-haul use, this interval is typically shortened to 120,000 miles (193,000 km).

For the Allison TC-10, the normal duty service interval is 150,000 miles (240,000 km). For severe-duty applications, which includes frequent stop-and-go driving, heavy loads, or operating in mountainous terrain, the interval is reduced to 100,000 miles (160,000 km).

Regularly checking the fluid level and condition is also recommended. If the fluid appears dark, burnt, or milky, it should be changed immediately, regardless of mileage.

Common transmission problems

The Eaton Fuller manual and automated transmissions are known for their durability, but they can still experience issues. Common problems include worn synchronizers, which can make shifting difficult, and air leaks in the pneumatic system of automated models, which can cause shifting problems.

The Allison TC-10 is also a robust transmission, but it can be susceptible to issues if not properly maintained. Overheating is a primary concern, often caused by low fluid levels or the use of incorrect fluid. Solenoid failures can also occur, leading to erratic shifting or a failure to shift altogether.

For any of these transmissions, addressing minor issues promptly is key to avoiding a major, costly repair. If you notice any unusual noises, vibrations, or shifting behavior, have the truck inspected by a qualified technician as soon as possible.

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