Spool Performance Stage 2 Upgraded Transmission Kit DIY (+1500Nm) - 8HP70, 8HP75, 8HP76

QT Parts is a Finnish online store.

Our warehouse is located in Nokia, Finland.

You can collect your order directly from us if needed. Simply select “Pickup” at checkout.

Pay securely with multiple payment methods, including invoice and installment plans through Klarna.

The delivery time for products in stock is 1-5 business days. We ship worldwide.

If the product is not in stock and it is a pre order product, the average delivery time is 5-21 business days. If the product has a longer delivery time than previously announced, we will be in touch. International orders may be subject to VAT, import duties, and customs fees upon arrival in the destination country.

Terms for product returns:

• You must return the ordered products within 14 days of receiving
• The products must be unused and without damages
• Commission fee for handling returns is 21,90€
• For product returns, the customer is in charge of the return costs. Only door to door service (Express)
• Shipping costs are not refunded

For international orders sales are final and non-refundable. Once an order is placed, it cannot be canceled or returned. By placing an order, you acknowledge and agree to these terms.

Return address: QT Parts, Vasarakatu 8B, 37150 Nokia, Finland.

Pre order / made-to-order products

If the product you have ordered is a pre order or made-to-order item, it is not subject to the 14-day right of withdrawal or return under consumer protection laws, as the product is manufactured or sourced specifically based on the customer’s individual order.

If you wish to cancel your order before receiving the product, we will refund 50% of the total order amount.

This condition applies to the following product categories:

• Suspension
• Engine Tuning
• Engine Parts
• Exhaust Systems
• Fueling
• Turbochargers/superchargers
• Drivetrain
• ECE-approved Downpipes

All of the above products are manufactured or sourced individually based on the customer’s order, and therefore cannot be returned after delivery, unless the product has a manufacturing or material defect.

In the event of such a defect, the standard liability for defects as provided by consumer protection legislation shall apply.

The Spool Performance Stage 2 transmission upgrade kit is designed for ZF 8HP series automatic transmissions with the goal of significantly increasing torque resistance and reliability in tuned engines. The result of over a year of testing and development, the kit enables torque levels in excess of 1200 ft-lb (~1600 Nm) while maintaining transmission driveability and functionality.

The kit addresses critical weaknesses in OEM designs, such as material limitations in C and E clutch hubs, and improves friction surface capacity, oil circulation, and temperature management.

Technical updates

Billet 7075 C and E clutch hubs

In ZF 8HP transmissions, the C and E hubs are known failure points because the original parts are made of cast aluminum (A380), which cannot withstand high torsional loads.

Spool Performance Solution:

• CNC machined billet centers from 7075 aluminum

• Heat-treated and hard-anodized surface

• Improved wear resistance and shear strength

• Optimized oil channels and cooling

• Larger clutch pack area

This prevents spline breakage and discs biting into the hub, which are typical OEM failure points.

FX-RT high friction coefficient friction surfaces

The friction plates in the series were developed in the Spool Performance laboratory.

• Higher coefficient of friction than OEM materials

• Better temperature resistance

• Stable engagement without slippage

• Maintains drivability in street driving

Together with the increased clutch packs, this significantly increases the torque capacity of the transmission.

Added clutch plate quantities

Each clutch pack has added plates and custom pressure and apply plates.

Benefits:

• Better torque resistance

• More even pressure distribution

• Less heat load per plate

Preset switch packages

All clutch packages are delivered with their clearances adjusted.

• Fast and safe installation

• No guesswork in clearances

• Includes additional steel plates for custom adjustments

Series content

• Billet 7075 C-hub

• Billet 7075 E-hub

• Hub center sleeve

• Friction plates and steel plates for A, B, C, D and E clutch packs

• Customized pressure and apply plates

• Complete seal kit (O-rings and gaskets)

• Additional steel plates for adjustment

Technical benefits

• Over 1200 ft-lb / 1600 Nm torque capacity

• Better clutch cooling and oil drainage

• Reduces spline breakage

• Improves the thermal resistance of the gearbox

• Maintains OEM-style drivability

Recommended transmission oil

AMSOIL Signature Series Fuel-Efficient 100% Synthetic ATF (Blue Cap)

Fit

• ZF 8HP70 (newer 48-spline versions only)

• ZF 8HP75

• ZF 8HP76

Used in the following models:

• BMW M5 F90

• BMW M8 F91 / F92 / F93

• BMW X3 M F97

• BMW X4 M F98

• BMW X5 M F95

• BMW X6 M F96

• BMW M3 G80

• BMW M4 G82 / G83

• BMW Alpina B7 G12

• BMW Alpina B8 G16