Spool Performance G90 ZF8HP100 Stage 2 Transmission Build

A Ground-Up Redesign for the Heaviest, Highest-Torque 8HP Platform 

The BMW G90 M5 and M5 Touring introduce a new era of drivetrain stress—extreme curb weight, enormous torque output, and the instantaneous jerk-loading created by the integrated electric motor. While the ZF 8HP100 is a formidable transmission, our recent teardown studies show that once the platform is tuned, the OEM clutch architecture is overwhelmed far sooner than expected.

Over the past several months, we disassembled multiple customer transmissions, each running a “Stage 2 tune” and each with only 4–5 months of real-world use. The internal condition was impossible to ignore.

The Findings: Shockingly Fast Clutch Deterioration

Inside these transmissions, we consistently discovered:

• Overheated, glazed, and darkened clutch packs

• Friction material breakdown far earlier than any other modern 8HP platform

• Steels showing heat spotting and surface instability

• Visible distortion and fretting on C and E hubs

• Uneven pressure distribution in the A and D clutch assemblies due to inherent OEM plate design flaws

This pattern repeated across multiple teardowns and multiple customer cars—making the conclusion clear:

The stock ZF 8HP100 internals are not built for tuned G90 torque curves and hybrid torque spikes.

Why does the G90 destroy clutches so quickly?

1. The mass.

The G90 is massive—well over 5,000 lbs in real operating conditions. This translates to dramatically increased load during launches, hard shifts, and rolling acceleration.

2. The tuned torque curve.

Stage 2 calibrations push output far beyond what ZF designed the clutch packs to handle—especially in midrange torque ramps.

3. Electric-motor jerk-loading.

The hybrid motor applies torque instantly at the exact moment clutch-to-clutch transitions occur, amplifying shock load by orders of magnitude.

No other BMW 8HP platform deals with this brutal combination of weight, torque, and hybrid aggression.

So we engineered a complete solution.

The Spool Performance Stage 2 G90 8HP100 Build

Engineered from the ground up for hybrid shock loads and high-torque abuse

7075-T6 Billet C & E Hubs — Reinventing the Core Structure

Our teardown studies showed distortion and wear patterns across the OEM hubs that simply should not occur in such a short time frame. We responded by designing new 7075-T6 billet hubs with:

• Massively increased yield strength

• Superior fatigue resistance under repeated hybrid torque pulses

• Tighter dimensional control for cleaner, more stable clutch engagement

• Improved oil windows and flow paths to stabilize clutch cooling during pressure transitions

While steel hubs could theoretically offer high strength, they pose a critical performance trade-off: weight.

7075-T6 aluminum provides:

• Nearly a 65–70% weight reduction compared to an equivalent steel hub

• Lower rotating mass, reducing inertia inside the drum assembly

• Faster clutch response because the transmission doesn’t need to accelerate or decelerate as much mass during shifts

• Reduced heat soak into surrounding components, as aluminum dissipates heat far faster than steel

Inside a transmission where every gram of rotating mass affects shift quality, thermal load, and component fatigue, the weight advantage alone makes 7075-T6 the superior choice for high-performance hybrid platforms.

All-New FX-RT Clutch Packs: Spool’s Latest High-Energy Friction System

At the center of our Stage 2 build is our new FX-RT friction system, a high-energy friction material engineered for extreme thermal loads, rapid engagement cycles, and hybrid torque environments.

FX-RT Friction Material Benefits

• High-energy capacity for prolonged slip control during aggressive shifting

• Thermally stable resin system engineered to prevent glazing and charring

• Predictable static/dynamic coefficient curve for smooth yet high-capacity engagement

• Improved oil flow geometry that helps extract heat during sustained load

• Superior resistance to material breakdown caused by hybrid jerk-loading

This is the most advanced friction system we’ve ever developed for an 8HP application—and the first specifically tuned for the torque signature of a hybrid performance platform.

Upgraded Steel Plates

To complement FX-RT friction, we designed new steels featuring:

• Improved surface finish for consistent coefficient behavior

• Enhanced flatness retention under repeated thermal cycles

• Reduced hot-spot formation

• Optimized thickness for high-speed pressure application

The combined pack dramatically increases overall torque-holding capability and longevity.

Custom Pressure Plates for A & D Clutches — Fixing OEM Weakness

During our teardown evaluations, the A and D clutch assemblies consistently showed uneven wear and poor cross-plate load distribution.

The culprit: OEM pressure plate geometry that distorts under heat and asymmetric load.

Our redesigned plates feature:

• Precision-machined billet construction

• A revised ramp and taper profile for perfectly uniform pressure application

• Reduced coning under thermal stress

• Cleaner, more stable hydraulic response

This upgrade is critical for preventing micro-slip in torque-heavy 2–3 and 3–4 shift events.

Why the G90 Needs This More Than Any Other BMW Platform

The G90 hybrid drivetrain is uniquely punishing, combining:

• Extreme vehicle weight

• High peak torque

• Instant torque hits from the electric motor

• Aggressive shift strategies

• Rapid thermal cycling in the clutch drums

The result is a transmission environment where OEM clutches and hubs are simply not built to survive.

Our Stage 2 system was engineered specifically for these real-world mechanical demands—not theoretical lab conditions. 

While we want to offer this as a DIY kit, the hybrid electric motor built into the transmission makes it a little more complicated needing special tools. We are currently planning to release this upgrade as a transmission build at spool service and to our experienced dealers worldwide. Stay tuned for more info on official release!