Building a Drivetrain Ready for 1,500 Horsepower
In the previous chapter, Grimace’s forged 3.4-litre S58 officially became a complete long motor, bringing our ambitious BMW G81 M3 Touring build one major step closer to reality.
Now, attention shifts beneath the engine.
While horsepower figures often steal the headlines, the drivetrain is ultimately responsible for delivering every kilowatt and every newton metre to the road. Without a transmission and transfer case capable of surviving extreme torque, even the strongest engine becomes little more than an expensive paperweight.
For Grimace, building a 1,500-horsepower engine was only half the equation.
The drivetrain needed to evolve alongside it.
Why Upgrade the Transmission?
BMW’s latest generation of ZF eight-speed automatic transmissions have earned an outstanding reputation throughout the performance industry.
Found in everything from BMW M cars to high-performance European vehicles around the world, the ZF 8HP platform has repeatedly proven itself to be one of the most capable automatic transmissions ever produced.
But as power levels climb well beyond factory expectations, even the legendary ZF8HP reaches its limits.
With Grimace targeting more than 1,500 horsepower from its fully built 3.4-litre S58 and future single turbo system, increasing clutch capacity and reinforcing critical internal components became essential long before the engine ever returns to the chassis.
Developing Customer Packages, Not Just One Build
One of the defining goals of the Grimace project has always been simple:
Only develop packages we’re prepared to stand behind.
Every major component fitted throughout this build has been carefully selected because it’s something we believe in - not simply because it’s popular.
For the transmission, EuroWerke partnered with Applied Torque Solutions (ATS), utilising their proven Stage 3 Performance Transmission Build while completing the entire assembly in-house.
Rather than outsourcing the work, Grimace continues to demonstrate our philosophy of investing in the tooling, knowledge and processes required to complete every major stage of the build under one roof.
That means the same team responsible for assembling Grimace’s engine is also responsible for building the transmission that will eventually deliver every horsepower to the road.
For us, that’s an important difference.
Because the ultimate goal has never been to build one impressive promotional vehicle.
It’s to develop complete, proven performance packages that we can confidently offer our customers in the future.
It’s the same development philosophy behind our BMW S58 performance packages, where hardware, ECU calibration and transmission strategy are developed as a complete combination rather than a collection of unrelated upgrades.
Inside the ZF 8HP
Before assembly began, the transmission was completely disassembled, cleaned and carefully inspected.
From there, the factory internals were upgraded using ATS Stage 3 performance components designed to significantly increase torque capacity while maintaining the drivability and refinement the ZF8HP platform is renowned for.
The upgraded transmission features:
- Complete transmission disassembly, inspection and cleaning
- ATS 4140 Performance Clutch Basket
- Upgraded clutch friction material
- ATS Performance Steels
- Enlarged clutch pack configuration
Together, these upgrades substantially increase clutch holding capacity while improving durability under the enormous torque loads expected from Grimace’s future single turbo powertrain.
At these power levels, reliability isn’t achieved by a single component - it’s the result of every internal part working together as a complete system.
Managing the Heat - WERKE Transmission Cooler
Increasing the mechanical capacity of the ZF 8HP is only part of preparing the transmission for the demands ahead.
As power, torque and sustained load increase, so does the importance of managing transmission temperature. Keeping temperatures under control helps maintain consistent transmission performance, particularly in tuned vehicles operating under sustained high-load conditions.
For Grimace, that means complementing the upgraded transmission internals with the WERKE Transmission Cooler.
Developed by WERKE for tuned vehicles, towing and sustained high-load driving, the WERKE Transmission Cooler is a performance transmission-cooling upgrade engineered for improved heat management and more consistent transmission temperatures.
Its application-specific design and fitment allow the cooling upgrade to become part of the overall transmission package rather than simply an additional universal component.
Key features include:
- Improved heat management
- More consistent transmission temperatures
- Application-specific design and fitment
- Developed for tuned vehicles, towing and sustained high-load driving
For Grimace, transmission cooling is being approached in exactly the same way as the transmission build itself: as part of a complete system.
Increasing torque capacity is one side of the equation. Ensuring the transmission can manage the additional thermal load that comes with sustained performance is the other.
The objective isn’t simply to build a transmission capable of surviving an impressive dyno number.
It’s to develop a complete package capable of doing the job consistently.
Strengthening the Transfer Case
The transmission isn’t the only component responsible for handling four-figure horsepower.
Sitting directly behind it, BMW’s ATC13 transfer case plays an equally critical role by distributing torque between the front and rear axles through the xDrive system.
As engine output increases, so too does the stress placed on every internal component throughout the drivetrain.
Like the transmission, Grimace’s transfer case has been stripped, inspected and upgraded in preparation for the power that lies ahead.
By strengthening both the transmission and transfer case together, the entire driveline is being developed as one complete package - ensuring every component is ready before the engine ever produces boost.
Everything Under One Roof
One theme has remained constant throughout the Grimace build.
Nothing leaves EuroWerke unless absolutely necessary.
From engine assembly and machining through to transmission building, fabrication, drivetrain strengthening and final calibration on our Mainline ProHub 3600CS AWD Hub Dyno, every stage remains under one roof.
Our continued investment in in-house dyno development forms an important part of that process, allowing increasingly powerful combinations to be assembled, calibrated and validated within the same facility.
That level of control allows every component to be assembled, inspected and validated by the same team that will ultimately calibrate the completed vehicle.
It also means every package we develop is firstly proven on our own promotional vehicle before becoming something we can confidently recommend and offer to our customers.
Grimace isn’t simply our workshop car.
It’s our engineering platform.
Build Progress
✅ Chapter 1 - Bottom End: From 3.0L to 3.4L
✅ Chapter 2 - Marrying the Head
✅ Chapter 3 - Transmission & Transfer Case Build - 15 September (Current)
⬜ Chapter 4 - The Single Turbo Transformation - 15 October
⬜ Chapter 5 - Everything Behind the Power
⬜ Chapter 6 - First Start
⬜ Chapter 7 - Calibration & Dyno Tuning
⬜ Chapter 8 - Testing & Drag Racing
What’s Next?
With Grimace’s transmission and transfer case prepared for the power targets ahead, attention now returns to the engine bay for one of the most anticipated stages of the entire build.
In Chapter 4 - The Single Turbo Transformation, the factory twin-turbo system makes way for an entirely new power package centred around the Garrett G45.
But the turbocharger itself is only one piece of the puzzle.
Chapter 4 will bring together the Pulsar exhaust manifold, RK intake manifold, upgraded fuel system, port injection and pumps, cooling and heat-exchanger plumbing, charge piping and the extensive fabrication required to integrate everything into the G81.
The exhaust system will also evolve around the new combination, including a custom downpipe, modified and V-banded WERKE midpipe, Performance Exhaust fabrication and CS titanium rear muffler.
It represents the next major step in the development of a platform we have spent years working with. Read more about why we consider the BMW S58 one of the strongest modern tuning platforms before Grimace moves well beyond the limits of a conventional bolt-on build.
This is the point where the individual systems required to support Grimace’s power target begin coming together as one complete package.
Chapter 3 prepares the drivetrain to survive the power. Chapter 4 builds the systems that will make it.
Stay tuned as Grimace enters its next phase.
Watch Chapter 3
Watch Grimace’s ZF 8HP transmission and BMW ATC13 transfer case stripped, upgraded and rebuilt in-house, along with the supporting transmission cooling upgrades being developed for the complete package.
Frequently Asked Questions
Why upgrade the ZF 8HP transmission?
Although the factory ZF8HP is an exceptionally capable transmission, high-horsepower applications place significantly greater demands on the clutch packs and internal components.
Performance upgrades increase torque capacity and durability while retaining the drivability that has made the ZF 8HP such a capable platform.
What does a Stage 3 transmission build include?
A Stage 3 transmission build typically includes complete disassembly, upgraded clutch baskets, performance friction materials, stronger steels and enlarged clutch packs to substantially increase holding capacity for high-output engines.
Why upgrade the transmission cooler?
As power and sustained load increase, controlling transmission temperature becomes increasingly important.
The WERKE Transmission Cooler is designed to improve heat management and maintain more consistent transmission temperatures, making it particularly suited to tuned vehicles, towing and sustained high-load driving.
Why upgrade the transfer case as well?
The transfer case distributes engine torque between the front and rear axles through BMW’s xDrive system.
As power increases, strengthening the transfer case helps ensure the entire drivetrain is capable of reliably handling the additional load rather than concentrating upgrades solely on the engine and transmission.
Why does EuroWerke build transmissions in-house?
Completing transmission builds in-house allows EuroWerke to maintain complete quality control while developing proven performance packages that can be confidently supplied and supported for future customer builds.
Can EuroWerke build high-performance ZF8HP transmissions?
Yes. EuroWerke offers in-house performance transmission builds using proven components for customers looking to increase the torque capacity and durability of BMW’s ZF8HP platform.
Components Featured in This Chapter
- ZF 8HP Automatic Transmission
- ATS Stage 3 Performance Transmission Build
- ATS 4140 Performance Clutch Basket
- Upgraded Clutch Friction Material
- ATS Performance Steels
- Enlarged Clutch Pack Configuration
- WERKE Transmission Cooler
- BMW ATC13 Transfer Case
Missed Chapter 2?
If you’re just joining the journey, start with Grimace Build Series - Chapter 2: Marrying the Head, where Grimace’s fully CNC-ported cylinder head is assembled before being united with the forged 3.4-litre stroker bottom end to complete the long motor.
Or head back to Chapter 1 - From 3.0L to 3.4L to see where the latest evolution of Grimace’s S58 began.
Grimace isn’t simply our promotional vehicle - it’s our in-house engineering platform, helping us develop and validate the next generation of high-performance BMW packages before offering them to our customers.
We’ll see you in Chapter 4. 💜
