5R55S vs 5R55W vs 5R55N: Ford Explorer Transmission Identification

Ford built three similar-but-different 5-speed automatics for the 1999-2010 Explorer, Mountaineer, Sport Trac, Aviator, and Mustang. The 5R55N, 5R55W, and 5R55S look almost identical externally. They're not interchangeable. Buying parts for the wrong one is the most common Explorer owner mistake.

Here's how to tell them apart and get the right parts.

Quick identification

| Trans | Years | Applications |
|---|---|---|
| 5R55N | 1999-2001 | Lincoln LS, Jaguar S-Type |
| 5R55W | 1999-2007 | Explorer, Mountaineer, Sport Trac (4.0L V6, 4.6L V8) |
| 5R55S | 2002-2010 | Mustang, Explorer, Mountaineer, Aviator (with EATX features) |

The 5R55S replaced both 5R55N and 5R55W in their respective applications as production continued.

The N vs W vs S meaning

  • N = original electronic 5-speed, for premium cars (Lincoln, Jaguar)
  • W = "Wide ratio" — adapted for SUVs and trucks
  • S = "Synchronous" — refined version with better shift quality

Key internal differences

5R55N (1999-2001)

- 5-speed, no alternate gear ratios - Used in Lincoln LS, Jaguar S-Type - Premium car application - Limited production

5R55W (1999-2007)

- 5-speed with wider gear spacing - Designed for SUV/truck applications - More truck-friendly low gear - Higher torque capacity than 5R55N

5R55S (2002-2010)

- Refined electronic control - Synchronous shift logic (smoother shifts) - Used in Mustang and updated SUV applications - Has shift solenoid placement differences vs W

The 5R55S is the most refined of the three. The 5R55W is the workhorse truck variant.

How to identify which one you have

Method 1: Year + application

- Lincoln LS or Jaguar S-Type 1999-2001: 5R55N - Explorer/Mountaineer 1999-2005 (4.0L V6): 5R55W - Explorer Sport Trac 2001-2005 (4.0L): 5R55W - Aviator, Mustang, post-2005 Explorer V8: 5R55S

Method 2: VIN decoder

The original RPO code is best determined through a Ford dealer with your VIN. Tells you the original equipment.

Method 3: Solenoid pack

- 5R55N: 4-pin solenoid pack connector - 5R55W: 6-pin solenoid pack connector - 5R55S: 8-pin solenoid pack connector

Quick visual check at the case-side connector.

Method 4: Date code on case

Stamped on the right side of the case. Cross-reference with year ranges.

Common failures across all three

1. Solenoid pack failure (most common)

All three trans share solenoid pack reliability issues. Heat + electrical wear kills them around 100-150K miles.

Symptoms: harsh shifts, slipping, DTCs (P0750-P0770 range), limp mode
Fix: solenoid pack replacement ($300-500 part)

2. Forward clutch wear

Standard wear over 150K miles in normal use.

Fix: full forward clutch replacement during rebuild

3. Reverse drum failure

The reverse drum can crack under hard use, especially in Sport Trac and Explorer tow applications.

Fix: Sonnax billet reverse drum during rebuild

4. Valve body bushings

Worn bushings cause harsh shifts.

Fix: Sonnax valve body bushing kit

5. Pressure regulator wear

Worn PR valve causes harsh or soft shifts.

Fix: Sonnax PR valve kit

Rebuild kit recommendations

Stock Explorer / Mountaineer 4.0L V6 (daily driver)

- Master rebuild kit with Alto frictions - All steels, bushings, seals - Solenoid pack replacement - Filter and pan gasket - Stock-style torque converter - Cost: $1,000-1,500

Mustang or performance application

- Above plus HD friction packs in 2-4 clutch - Sonnax billet reverse drum - TransGo shift kit - Performance torque converter - Cost: $1,400-2,200

Sport Trac / Aviator tow application

- Above plus larger external cooler - HD valve body - Solenoid pack with HD wiring - Cost: $1,500-2,500

What kills 5R55 series early

1. Wrong fluid

5R55N/W (1999-2008): Mercon V 5R55S (2002+): Mercon V originally, Mercon LV in some late applications

Always verify before topping off. Mixed fluids cause shudder.

2. Heavy towing

The 5R55W in Explorer is rated for 5,000-7,000 lbs tow. Pulling at the rating limit shortens life dramatically.

3. Skipped service

Ford's "lifetime fill" is aggressive. Service every 30-50K miles to extend life.

4. Engine heat (Explorer specific)

Some Explorer V8 cooling configurations run trans hot. Add external cooler.

Fluid

  • 5R55N, 5R55W: Mercon V
  • 5R55S (2002-2007): Mercon V
  • 5R55S (2008+): Mercon LV in some applications

Verify spec on door jamb sticker or owner's manual. Wrong fluid = shudder + accelerated wear.

Capacity: about 13 quarts total, 6 quarts in pan.

What about 5R44E?

The 5R44E is a related 4-speed (not 5-speed despite the name). Used in older Explorer applications. Different rebuild kits than 5R55 series.

Cost summary

DIY rebuild (parts only)

- Stock 5R55W: $1,000-1,500 - Performance 5R55S: $1,400-2,200

Shop rebuild installed

- Quality independent: $2,200-3,500 - Specialty Ford shop: $2,800-4,200

Reman swap

- Quality reman: $2,800-3,800 installed - Often with 36-month warranty

When to swap out vs rebuild

For Explorers and Mountaineers worth less than $5,000, rebuild only if you really like the vehicle. For Aviators and Sport Tracs worth more, definitely rebuild.

For Mustangs with 5R55S, definitely rebuild (or upgrade to manual swap if performance-minded).

---

Need 5R55N, 5R55W, or 5R55S rebuild parts? Shop our 5R55W catalog and 5R55S catalog. Master kits, solenoid packs, Sonnax billet drums, valve body kits, Alto frictions. Free shipping over $70. Same-day ship in-stock.

Related guides:
- How to identify your Ford transmission
- 4R70W rebuild guide
- Transmission fluid guide