RE4R01A Transmission Master Rebuild Kit, Nissan Pathfinder

If the automatic in your Nissan Pathfinder has started flaring between gears, slipping when it should be pulling, or sitting a second too long before it grabs Drive, the clutches inside the RE4R01A are usually what is giving up. This master overhaul kit is the soft-parts package for that rebuild: friction plates, steel plates (shown in the kit photo), the pan, case and valve body gaskets, lip seals, sealing rings and O-rings. It references OE kit numbers B075820A, B075880A and W075881A, carries manufacturer number BL-10035221, and ships from the USA.

What the master kit does in an RE4R01A

The RE4R01A is Jatco's 4R01 rear-drive four-speed, built for Nissan from 1988 through 2004. Mazda used the same family under the R4A-EL name, which is why that code turns up in parts catalogs next to the Nissan one. Every gear is made by applying a combination of multi-plate clutches and brakes with oil pressure, and every apply circuit depends on rubber seals and sealing rings holding that pressure. When the frictions glaze or a seal shrinks, the clutch slips, heats up, and starts shedding material. A master kit replaces all of the parts that wear and harden in one pass, so the rebuilt unit is not relying on a 20-year-old piston seal next to a brand new clutch pack.

Symptoms that point to a rebuild

• Slip or flare on the 2-3 or 3-4 upshift, especially loaded or towing
• Delayed engagement into Drive or Reverse when cold
• Dark, burnt-smelling fluid with friction material on the pan magnet
• Loss of third gear or forward drive after the unit overheats
• Fluid weeping from the pan, front pump or extension housing seals

TransGo's RE4R01A instructions list the failures that bring these units back: third or forward clutch burn-up, an inner 3-4 clutch seal that leaks, and sealing rings that shrink. All three are soft parts this kit replaces. The same sheet warns that this transmission does not tolerate clutch or lockup lining debris, because the fuzz plugs the filter and screens, drops line pressure and can take the planetary gears with it.

How to confirm it before you buy

Pull the pan and look at what is on the magnet and in the filter. Our ATF color and smell chart shows what burnt clutch fluid looks like compared with fluid that is just old. If you are not sure whether you are feeling a slip or a flare, read shift flare vs. slip first. A slip under load with debris in the pan means the clutches are done, and a fluid change will not bring them back. If the case is cracked or the planetaries are blued, weigh the options in our rebuild vs. replace vs. reman guide.

Fitment

This kit is listed for the Nissan Pathfinder with the RE4R01A automatic. The listing does not narrow it to specific model years, and Nissan refined this transmission when the unibody R50 Pathfinder arrived for 1996, so read the model code on the case tag or send us your year and VIN before you order. The RE4R03A and the five-speed RE5R05A that replaced this unit are different transmissions and will not take these frictions. If your Pathfinder has the later five-speed, you need the RE5R05A master rebuild kit instead.

Install notes

• Tear the unit down fully, then inspect drums, bushings, the pump and the planetary gears. Hard parts are not in this kit.
• Soak every new friction in clean ATF before assembly, and set each pack clearance with the selective plates rather than trusting the old stack height.
• Fit the new sealing rings carefully and check that they turn freely in their bores before the drum goes back in.
• Replace the internal filter at the same time; the Ecogard XT1229 filter kit is listed for the RE4R01A.
• Flush the cooler and lines before the rebuilt unit goes in. TransGo recommends adding an auxiliary cooler such as the Derale 13316 tube-fin cooler, because the factory cooling is marginal and plugs easily. Our cooler flush guide walks through it.
• Refill with the Nissan-specified ATF shown in your owner's manual and check the level hot.

Will this kit fit my Pathfinder?

It is listed for the Nissan Pathfinder with the RE4R01A four-speed automatic. Read the model code on the transmission tag or send us your year and VIN, because later Pathfinders moved to the five-speed RE5R05A, which this kit does not fit.

Is the RE4R01A the same as the R4A-EL?

They come from the same Jatco 4R01 family. Nissan calls it the RE4R01A and Mazda calls its version the R4A-EL. Internal parts can differ between applications, so match the case tag on your unit.

What is not included?

Hard parts. Drums, bushings, the pump, planetary gears, the filter and the torque converter are not in this kit. Inspect them during teardown and order any worn pieces separately.

Why do rebuilt RE4R01A units come back?

TransGo points to clutch and lockup lining debris plugging the filter and screens, leaking 3-4 clutch seals and shrunken sealing rings. Flushing the cooler, fitting a new filter and adding an auxiliary cooler addresses most of that.

What fluid does it take after the rebuild?

Use the Nissan-specified automatic transmission fluid listed in your owner's manual, and set the level with the transmission at operating temperature.

• Shift Flare vs. Slip: How to Tell Them Apart
• ATF Color and Smell: What Your Transmission Fluid Is Telling You
• How to Flush a Transmission Cooler After a Failure
• Rebuild vs. Replace vs. Reman Transmission