RE4R01A Transmission Filter Kit, Nissan Pathfinder Xterra Frontier

This is the drop-in filter and pan gasket for the Nissan RE4R01A four-speed automatic (also carried as RL4R01A and RE5R01A), the longitudinal transmission Nissan ran behind the VG30/VG33 and later 4.0L V6 in its trucks and SUVs. It replaces OEM 31728-41X01 and 31728-41X03 and cross-references to FRAM FT1138 and FT1145, Purolator P1229, WIX 58906, and Mazda BV11-19-815. You will find this transmission in the Nissan Pathfinder (1987-2004), Xterra (2000-2004 3.3L and 2009-2013 4.0L), Frontier (1999-2010), D21 and Pickup, the Infiniti QX4, the Mazda MPV, 929 and B2600, and the Suzuki Equator.

On the bench the job is straightforward. Drop the pan, unbolt the old spin-off filter from the valve body, and set the new one in before you reseal the pan on the fresh gasket that comes in the kit. Nissan built a few variants of this pan and filter over the years, so before you button it up, hold the new filter next to the one you pulled and check that the pickup neck length matches - a longer neck will hold the pan off the case. Torque the pan bolts evenly and refill with Nissan-spec ATF (Matic-D or a compatible multi-vehicle fluid) to level.

A clogged RE4R01A filter starves the pump and shows up as a slip or flare on the 1-2 and 2-3 shifts, a delayed or harsh engagement when cold, or a whine as the pump pulls against the restriction. These screens load up with clutch material as the miles climb, so on a high-mileage Pathfinder or Frontier the filter goes back in new with every fluid service rather than getting cleaned and reused. Verify fitment against the 31728-41X01 OEM number for your year and drivetrain before installing.