RE5R05A Pump 2003-2006

The 2003-2006 RE5R05A trucks are now old enough that high mileage and years of overdue fluid changes have caught up with them. If your early Nissan Titan, Armada, Frontier, Pathfinder or Xterra, or Infiniti QX56, now crawls into gear on a cold start, moans at idle or slips on a long climb, a worn front pump is a likely cause. This is a used original pump assembly listed for the 2003-2006 production window, for owners and shops putting an early unit back on the road.

Why the pump matters on an early RE5R05A

The RE5R05A first appeared in the 2002 Infiniti Q45 and spread through the Nissan and Infiniti rear-drive and truck lineup from there. On every version, the front pump is turned by the torque converter hub and produces all of the oil pressure the unit uses, from clutch and band apply to converter clutch apply and lubrication. Early units have had the most years for abrasive fluid to wear the pump pocket and gears. Each thousandth of extra clearance is another place for pressure to bleed off, and it shows up as softer, slower applies everywhere at once.

Symptoms on 2003-2006 units

• Long delay going into Drive or Reverse after the truck sits, improving somewhat as it warms
• A cold whine or moan that follows engine RPM
• Slipping on every upshift under load, such as towing or climbing
• Fluid that smells burnt or has turned dark well before the service interval
• Pressure complaints with no solenoid code stored, which points away from the electrical side

Diagnose before you buy

Gauge the line pressure port cold and hot. A worn pump usually makes acceptable pressure cold, when thick fluid helps seal the clearances, and falls off as the fluid heats. Before you commit, look at the valve body too: Sonnax notes three different RE5R05A valve body designs, and worn pilot valve bores can drop line pressure just like a weak pump. Pull a fluid sample and look for a milky or pink tint. Sonnax reports water intrusion from failed radiator coolers in roughly half the RE5R05A cores they receive, and on an early truck with its original radiator, that is a real risk. Our RE5R05A service guide covers the full pressure test sequence and what to check in the pan.

Fitment

This pump is listed for 2003-2006. That range spans the early RE5R05A production years, and the transmission picked up revisions as it went, so do not assume one pump fits every truck in the window. Compare the pump body casting, bolt holes and stator shaft to the pump you are replacing, or send us your year and VIN before ordering. If your truck is a 2007, see our 2007 RE5R05A pump instead. Browse all early and late parts on the RE5R05A transmission page.

Install notes

• Fit a new front seal and check the pump bushing. On a high-mileage early unit, look hard at the converter hub for a wear groove at the seal.
• Inspect every steel sealing ring land with magnification. Gears Magazine documented ring land wear on an aging RE5R05A support at more than three times the 0.005 inch expected clearance, and recommends an air check at no more than 50 psi after assembly.
• Pre-lube the pump gears, tighten the pump evenly to the case, and confirm the converter is fully engaged with the pump drive before installing the transmission.
• Fill with Genuine Nissan Matic S ATF and check the level hot.
• An early unit with a worn pump has usually worn its frictions as well. Our RE5R05A master rebuild kit for the Titan or the 2005-2011 Banner rebuild kit covers the seals, gaskets and clutches while the case is open. Replace the radiator cooler if it is original or suspect.

Does this pump fit all 2003-2006 RE5R05A transmissions?

It is listed for the 2003-2006 range, but the RE5R05A had revisions during those years. Match the casting, bolt pattern and stator shaft to your old pump, or send your year and VIN and we will confirm before you order.

My 2005 Pathfinder only whines when cold. Is that the pump?

A cold whine that follows engine RPM is a common pump wear sign, because worn clearances let air into thick cold fluid. Confirm it with a hot and cold line pressure test before pulling the transmission.

Should I rebuild the rest of the transmission at the same time?

If the fluid was burnt or contaminated, yes. The clutches ran on the same fluid that wore the pump. A master rebuild kit costs little compared to pulling the transmission twice.

Why replace the radiator cooler on an early truck?

Sonnax reports that about half of RE5R05A cores show water intrusion from failed radiator coolers. On an early truck with an original radiator, replacing it protects the new pump and clutches.

What fluid do I fill it with?

Genuine Nissan Matic S ATF, or Matic J as Nissan's approved alternative. Check the level hot using Nissan's procedure.

• Nissan/Infiniti RE5R05A Transmission Service Guide: Pathfinder, Armada, QX56