MERCURY 400-04651 Automatic Transmission 5W7P-AA

( Part Type: Transmission ), ( Conditions Options: A, 4.6 ), ( Genuine Oem: Yes ), ( Ipn: 400-04651 )

Review MERCURY Automatic Transmission Id fits CROWN VICTORIA 2005

The **Mercury 400-04651 Automatic Transmission (5W7P-AA, 05 Crown Victoria)** is a high-performance, factory-specification transmission designed exclusively for the 2005 model year of the iconic **Mercury Crown Victoria**, particularly those equipped with the **4.6L V8 engine** (commonly paired with the **4-speed automatic transmission**). This transmission is a critical component in the drivetrain, ensuring smooth power delivery, precise shifting, and reliable operation under the demanding conditions of daily driving, highway cruising, and towing light loads. Built to Mercury s stringent quality standards, the 400-04651 features a robust **torque converter** with a **stator and pump assembly** optimized for efficient fluid circulation, reducing heat buildup and extending transmission life. The **valve body** is meticulously engineered to regulate hydraulic pressure, enabling seamless gear transitions from **Park (P) to Reverse (R), Neutral (N), Drive (D), and Low (L)**, while the **planetary gear set** delivers strong torque multiplication for both acceleration and towing applications. Constructed from high-grade **steel and aluminum alloys**, the transmission case is reinforced for durability, with precision-machined internal components that minimize wear and friction. The **5W7P-AA** designation confirms its compatibility with **Mercedes-Benz 5-speed automatic transmission fluid (5W-70)**, which provides excellent thermal stability and protection against oxidation, ensuring long-term performance even in extreme temperatures. Whether used in a **police interceptor, luxury sedan, or fleet vehicle**, this transmission is engineered to handle the demands of heavy-duty operation while maintaining the Crown Victoria s legendary reliability. For restoration projects or replacement purposes, the 400-04651 is a direct-fit, OEM-quality transmission that restores factory performance, making it an essential part for enthusiasts seeking to preserve or enhance the driving dynamics of their 2005 Crown Victoria.

### **Pros and Cons of Buying a Mercury 400-04651 Automatic Transmission (5W7P-AA, 05 Crown Victoria)**

1. **Compatibility** The 400-04651 transmission is a direct replacement for the 5W7P-AA unit found in the 2005 Crown Victoria, ensuring a seamless fit without modification.

2. **Proven Reliability** The 400 series transmissions (especially Ford s 4-speed automatics) are well-regarded for durability when properly maintained, making them a solid choice for classic or high-mileage vehicles.

3. **Aftermarket Support** This transmission is widely available from both OEM and aftermarket suppliers, including brands like **Mercury, Ford, and reputable rebuilders**, ensuring easy sourcing.

4. **Cost-Effective Alternative** Compared to a fully rebuilt OEM unit, a used or rebuilt 400-04651 can be significantly cheaper while still offering good performance.

5. **Common Modifications** Many owners upgrade to **heavier-duty torque converters, valve bodies, or solenoids** to improve shifting and longevity, making it adaptable to different driving conditions.

6. **Community Knowledge** The 5W7P-AA is a well-documented transmission, with extensive forums (e.g., **Ford Crown Victoria forums, Transmission Home, or Classic Ford forums**) offering troubleshooting and modification tips.

7. **Potential for Long-Term Use** With proper maintenance (fluid changes, filter replacements, and occasional inspections), this transmission can last **150,000 miles**, especially in a Crown Victoria with a strong engine (e.g., 4.6L V8).

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1. **Age and Wear** The 2005 Crown Victoria was already nearing the end of its production run, and many units may have **high mileage or pre-existing wear** (e.g., worn clutches, solenoid issues, or fluid breakdown).

2. **Fluid and Filter Neglect** Many owners fail to change transmission fluid regularly, leading to **slipping, rough shifting, or internal damage**. Always verify fluid condition before purchase.

3. **Common Failure Points**

- **Solenoids** (can fail and cause shifting issues).

- **Torque converter** (may need replacement if slipping occurs).

- **Clutch packs** (wear over time, especially in stop-and-go driving).

- **Valve body** (can develop leaks or electrical issues).

4. **Rebuild Quality Variability** If purchasing a **rebuilt unit**, quality varies widely. Some rebuilders cut corners, leading to **premature failure**. Research the supplier s reputation.

5. **Electronic Issues** The 5W7P-AA relies on **PCM (Powertrain Control Module) communication**, so wiring or sensor problems (e.g., speed sensor, shift solenoids) can cause malfunctions.

6. **Limited Modern Support** Unlike newer transmissions, finding **specialized mechanics** familiar with this unit may be harder, increasing repair costs if issues arise.

7. **Potential for Hidden Damage** Without a **full inspection (fluid analysis, leak checks, shift test)**, internal damage (e.g., bent shafts, worn bearings) may not be apparent until after installation.

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### **Conclusion**

The **Mercury 400-04651 (5W7P-AA) transmission** is a **solid choice for a 2005 Crown Victoria** if you prioritize **cost-effectiveness, availability, and reliability** provided it is **properly inspected and maintained**. It is well-suited for **enthusiasts who enjoy working on their vehicles** or those who can afford occasional repairs. However, if you seek a **plug-and-play, low-maintenance solution**, a **fully rebuilt unit from a trusted shop** (with a warranty) is essential to avoid future headaches.

- **Buying from a reputable transmission specialist** (e.g., **Transmission Home, Ford Performance Parts, or a local rebuild shop**).

- **Getting a fluid analysis** to check for contamination or breakdown.

- **Testing the transmission** (if possible) for smooth shifting and no leaks.

- **Budgeting for potential upgrades** (e.g., **heavy-duty torque converter, upgraded solenoids**).

If you re **not comfortable with transmission maintenance**, a **new or remanufactured OEM unit** (if available) may be worth the higher cost for peace of mind.

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You have **mechanical experience** or access to a **trusted mechanic** for installation and maintenance.

You **verify the unit s condition** (fluid, shifting, no leaks) before buying.

You re **prepared for potential repairs** (solenoids, torque converter, etc.).

You **plan to keep the vehicle long-term** and are willing to invest in upkeep.

You want a **completely hassle-free** transmission without any risk of failure.

You **cannot afford** unexpected repairs or modifications.

The **selling source cannot provide proof of maintenance** (fluid changes, rebuild quality).

For most **average buyers**, a **rebuilt 400-04651 from a well-reviewed shop** is a **good balance of cost and reliability**, but **expect to spend extra on maintenance** to keep it running smoothly. If budget allows, a **new or high-quality remanufactured unit** may offer better long-term confidence.

Details:

GRAND MARQUIS 05 AT; ID 5W7P-KA. CROWN VICTORIA 05 AT; ID 5W7P-KA. Larger items.e. No expedited shipping is available.

CROWN VICTORIA 05 AT; ID 5W7P-AA. GRAND MARQUIS 05 AT; ID 5W7P-AA.

part #: 400-04651 prices

• $885.10-$1123.60

specifications autotransmissionsgo:

• for models: Crown, Victoria
• for makes: Mercury
• for years: 2005
• part type: Transmission
• conditions options: A, 4.6
• genuine oem: Yes
• ipn: 400-04651

returns autotransmissionsgo:

• policy: Returns Accepted
• time: 60 Days
• paid by: Seller

offer autotransmissionsgo:

• started: April 6, 2026
• availability: In Stock
• quantity: 1
• options: Ship-to-home
• best offers: True
• sold: 0

shipping autotransmissionsgo:

• class: Freight
• cost: $0.00
• service: Flat Rate Freight
• type: Fixed

seller autotransmissionsgo:

• # reviews: 6256
• rating: 96.7%
• city: Beaver, Pennsylvania

payments autotransmissionsgo:

• wallet: Apple-pay
• credit card: Discover
• other

general autotransmissionsgo:

• Car Truck Parts Accessories > Transmission Drivetrain > Automatic Transmission
• condition: Used

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