2018 Ford F-250 Super Duty Transmission Fluid & Service Guide

The 2018 Ford F-250 Super Duty is a workhorse, built to handle heavy payloads, serious towing, and brutal job site conditions. Depending on your engine choice—the 6.2L gas V8 or the mighty 6.7L Power Stroke V8 turbo diesel—your truck is equipped with one of two extremely capable six-speed automatic transmissions. Maintaining these gearboxes is critical to keeping your Super Duty on the road and avoiding catastrophic failure.

As an ASE-certified master technician, I’ve serviced countless Ford TorqShift transmissions. Here is everything you need to know about the transmission fluid, capacity, filters, and service intervals for the 2018 Ford F-250 Super Duty.

Quick Answer: 2018 Ford F-250 Transmission Specs

• Transmission Make/Model: Ford 6R100 TorqShift-G (6.2L Gas) / Ford 6R140 TorqShift (6.7L Diesel)
• OEM Fluid Spec: Motorcraft MERCON® LV (Both transmissions)
• Drain & Fill Capacity:
  • 6R100: Approx. 6.0 – 7.5 quarts
  • 6R140: Approx. 7.0 – 9.0 quarts
• Full Overhaul / Dry Capacity:
  • 6R100: 14.8 quarts
  • 6R140: 16.7 quarts
• Filter OEM Part Number:
  • 6R100: FL3Z-7A098-B (verify with dealer based on VIN)
  • 6R140: BC3Z-7A098-B (verify with dealer based on VIN)
• Recommended Service Interval: 150,000 miles (Normal Duty) / 60,000 miles (Severe Duty / Frequent Towing)

Fluid Type Explained

For the 2018 Ford F-250 Super Duty, Ford specifies Motorcraft MERCON® LV Automatic Transmission Fluid for both the 6R100 and the heavier-duty 6R140.

MERCON LV stands for "Low Viscosity." It is specifically formulated to provide better fuel economy, superior shift feel at low temperatures, and excellent thermal stability to protect against deposits and sludge under heavy towing loads. Do not confuse this with older fluids like MERCON V or SP, and do not use the newer MERCON ULV (which was introduced for the 10-speed transmissions in 2020+ models). Using the wrong fluid can cause irreversible damage to the clutch friction materials and the valve body.

Service Procedure: Drain & Fill vs. Full Exchange

When servicing the TorqShift transmissions, you generally have two options: a standard drain and fill (pan drop) or a full fluid exchange.

The Drain and Fill (Pan Drop): This is the preferred method for most technicians. By dropping the transmission pan, you drain roughly half of the total fluid capacity (around 7 to 9 quarts on the 6R140). More importantly, this allows you to inspect the magnet at the bottom of the pan for excessive metal shavings and replace the transmission fluid filter. The 6R140 and 6R100 both use an internal filter that should be replaced during this service. Because the torque converter retains a significant amount of fluid, a simple pan drop will not replace 100% of the fluid.

Full Fluid Exchange (Flush): A fluid exchange machine taps into the transmission cooler lines to pump out the old fluid while simultaneously pumping in fresh fluid, replacing nearly 100% of the fluid. If you choose this route, ensure the shop drops the pan first to change the filter and clean the magnet, then performs the exchange. Never allow a shop to use chemical cleaning additives or "flush solvents," as Ford expressly advises against them; they can dislodge debris and ruin the solenoids.

Checking the Level: Both the 6R100 and 6R140 feature a dipstick located in the engine bay. Always check the fluid level with the transmission at operating temperature (195°F - 215°F), parked on a level surface, with the engine idling in Park.

Service Interval

Ford’s official maintenance schedule varies significantly depending on how you use your truck.

• Normal Duty: Ford states that the transmission fluid and filter should be changed every 150,000 miles. However, as a master technician, I rarely see trucks make it to 150k without degraded fluid. I highly recommend cutting this interval down to 90,000 miles for maximum longevity, even if you never tow.
• Severe Duty (Towing): If you frequently tow heavy trailers, use a slide-in camper, idle extensively, or operate in dusty/off-road environments, your truck falls under the "Severe Duty" schedule. Under these conditions, heat is the transmission's worst enemy. Ford recommends replacing the fluid and filter every 60,000 miles, and I strongly agree with this interval.

Common Transmission Problems

The 2018 generation of the 6R140 and 6R100 is highly regarded in the diesel and heavy-duty community for being remarkably robust, but they are not entirely immune to issues:

1. Shift Flares and Harsh Shifts: Especially on the 1-2 and 2-3 shifts. This can often be resolved by updating the Transmission Control Module (TCM) software or performing a relearn procedure with a bidirectional scan tool. In severe cases, it points to a sticking solenoid in the valve body.
2. Solenoid Failures: The shift solenoids on the 6R140 valve body can occasionally fail or become clogged by clutch material if fluid maintenance is neglected, resulting in a loss of certain gears or a Check Engine Light.
3. Torque Converter Shudder: Caused by degraded MERCON LV fluid failing to provide the correct friction properties for the torque converter lock-up clutch. A fluid exchange is often the cure if caught early.
4. Overheating Under Load: While rare thanks to massive factory transmission coolers, towing past the gross combined weight rating (GCWR) or a blocked cooler line can cause temperatures to spike past 230°F, severely shortening fluid life.

If you want to keep your TorqShift transmission shifting smoothly for half a million miles, stick to strict MERCON LV fluid intervals and always change that internal filter.

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