Spool Performance – Mercedes 725 9G FX-RT Upgraded Clutch Kit 

Rated for up to 1,700 Nm input torque

The Mercedes 725 9G transmission is a strong unit from the factory—but once torque levels push past the mid-700 Nm, the stock frictions and limited plate counts begin to slip, especially under repeated high-load, high-temperature conditions.

Spool Performance has developed a complete upgraded clutch system for the 725 9G using our FX-RT high-coefficient, high-energy friction material, the same proven technology that transformed the 8HP50 platform into a competition worthy transmission.

This new kit increases both the coefficient of friction (+20%) and the clutch counts across all six elements, dramatically increasing the torque capacity of every gear.

Clutch Count Increases

Combined with the FX-RT friction upgrade, the resulting torque-capacity increases are substantial.

Torque Capacity Gains (Per Gear)

Based on clutch engagement logic for the 9G and the combined friction + plate-count increases:

Final Torque Rating

The factory 725 9G is rated for 1000 Nm.
With the FX-RT clutch packs installed:

• 1st–4th gear clutch-limited rating: ≈1680 Nm

• 5th–9th gear clutch-limited rating: ≈1714 Nm

• Overall clutch-pack system capability: ≈1,700 Nm

This upgrade raises the clutch-limited torque threshold by +68–71%, depending on gear.

Why FX-RT?

Our FX-RT friction material was engineered specifically for high-torque, high-energy, fast-shift transmissions. It has been proven in our 8HP50 kits, where customers reliably push 900–1000 Nm. Now the same technology elevates the Mercedes 725 9G into a new performance class.

Benefits include:

• 20% higher μ for dramatically improved static and dynamic holding power

• Higher thermal stability under repeated high-load upshifts

• Reduced shift flare and reduced clutch slip

• Smoother, more consistent clutch apply characteristics

Who This Kit Is For

The Spool Performance 725 9G upgraded clutch kit is ideal for:

• High-power M177 builds

• GLE63 / GLS63 high-boost setups

• Tuned E63 / S63 running hybrid turbos

• Track-driven or heavy-use AMG applications

• Anyone targeting 1000+ crank hp with headroom

Your 725 9G is no longer the limiting factor. With Spool Performance FX-RT friction technology and increased clutch capacity, the transmission becomes capable of safely holding ~1700 Nm, giving your AMG the drivetrain headroom it needs to push big-power, high-boost builds confidently and repeatedly.

What’s Included

The Spool Performance 725 9G FX-RT Clutch Upgrade Kit includes all components required for a complete drop-in installation. No machining or custom fabrication is needed.

• Clutch A [B08] Pack (6-plate upgrade)

  • 6 x FX-RT friction discs

  • 6 x Upgraded Steel plates

  • 1 x Custom Pressure Plate
    

  Clutch B [B05] Pack (7-plate upgrade)

  • 7 x FX-RT friction discs

  • 7 x steel plates

  • 1 x Custom Pressure Plate
    

  Clutch C [B06] Pack (7-plate upgrade)

  • 7 x FX-RT friction discs

  • 7 x steel plates

  • 1 x Custom Pressure Plate

  Clutch D [K81] Pack (9-plate upgrade)

  • 9 x FX-RT friction+steel internal spline discs

  • 9 FX-RT friction+steel external spline discs

  • 1 x Custom Pressure Plate

  Clutch E [K38] Pack (9-plate upgrade)

  • 9 x FX-RT friction discs

  • 9 x steel plates

  • 1 x Custom Pressure Plate

  Clutch F [K27] Pack (10-plate upgrade)

  • 10 x FX-RT friction discs

  • 10 x steel plates

  • 1 x Custom Pressure Plate

Everything is pre-measured and packaged by clutch pack to ensure consistent clearances and simplified assembly. The kit is fully compatible with factory drums, pistons, and snap-ring locations.

Note: Please email customer_service@spoolperformance.us for details on scheduling training for installation of this component.

If your item is in stock and the order is placed before 3 PM, it will ship the same day. Products that include ceramic coating are shipped the following business day. If the product or color you’re looking for is out of stock, you can join the waitlist by clicking the “Email When Available” button. We’ll notify you as soon as it’s back and provide an estimated restock time.

Custom Orders
For custom requests, please email us directly. We’ll review your order and provide an estimated delivery time based on the required manufacturing process.

Damaged, Incorrect, or Missing Items
If your order arrives damaged, incorrect, or missing parts, simply email us a photo along with your order number. We’ll arrange a refund or exchange right away. Contact us at info@ttmengineering.se and we’ll make it right.

Returns & Satisfaction
Unused and uninstalled products are eligible for a refund, exchange, or store credit. Unfortunately, once a product has been used or installed, we cannot accept returns or offer refunds. If you decide you don’t like a product after installation, it will not qualify for return.

Restocking Fee
A restocking fee of 20% of the original purchase price may apply to returned products. This fee covers the costs of processing and restocking. Please refer to our Policies Page for full details on exchanges and returns.