RAYBESTOS 8L90 Performance Transmission Rebuild Kit & Billet Input Shaft - Level 3 (Drop-In Clutch Module, No Added Clutch Capacity)

Picture for representation purposes only - actual contents may vary as we continue to develop our product.

Billet Input Shaft (Drop-In, 300M Alloy Steel)

This billet input shaft is precision-machined from 300M alloy steel, one of the strongest materials on the market for high-load transmission parts. It is heat-treated to improve long-term durability and features an increased radius between the sealing rings to reduce stress fractures. Because the sealing rings come pre-installed, the shaft is a true drop-in component, eliminating the need for sealing-ring installers or sizing tools. It’s an ideal upgrade for builds that require added strength without fully re-engineering the 8L90 transmission.

Important: Multiple Versions of the 8L90 Input Shaft Exist

The 8L90 transmission was produced using different shaft designs depending on the model year, vehicle platform, and torque converter configuration. Ordering the correct version is crucial, using the wrong shaft can lead to pressure loss, poor engagement, or additional transmission issues down the road. Before you purchase, confirm the following:

What to Verify Before Ordering

• Model Year & Vehicle: Shaft design varies between early and late 8L90 units.

• Shaft Style: Identify whether your transmission uses the early-style or late-style spline pattern.

• Torque Converter Compatibility: Match spline count and hub size to your converter.

How to Verify Fitment

• Check your transmission’s build tag or serial number.

• Measure and count the splines on your existing shaft.

• Text a clear photo of your input shaft and converter hub to 713-895-7019.

If you’re unsure, our team can assist you before checkout to ensure proper fitment, helping you avoid delays, returns, and extra rebuild labor.

Raybestos GPZ® High-Energy Clutch Pack Module

This Level 3 kit includes a Raybestos clutch module featuring GPZ® High Energy fibers, designed to handle higher stress and heat than standard clutches. These materials maintain stability during repeated cycling, making them ideal for trucks, SUVs, and performance cars that see more load than stock. The pack also includes (5) C3 clutches when needed for transmissions equipped with the larger-capacity drum, ensuring compatibility across multiple 8L90 variations.

Raybestos Steel Pack Module

The included Raybestos steel module enhances shift feel and extends clutch life during a rebuild. These steels help reduce shudder, noise, and inconsistent pressure, common complaints among factory 8L90 units. With (5) C3 steels included for transmissions requiring the larger drum, this pack delivers a balanced and dependable upgrade for your build.

Overhaul Kit (Gaskets, Seals & Critical Soft Parts)

The overhaul kit provides the essential gaskets, seals, and soft components required for a complete and reliable 8L90 rebuild. Replacing worn internal seals helps restore hydraulic integrity, reduce pressure loss, and prevent common post-rebuild failures. This upgraded overhaul kit supports consistent performance whether you’re on the track, towing, or on the open road.

Hi-Per Blue® C1 Piston

The Hi-Per Blue® piston for the C1 clutch pack (1-2-7-8-R) is made from advanced high-performance AEM material for superior thermal and chemical resistance. This gives the piston increased stability during high-load apply cycles, helping your transmission maintain smooth, consistent engagement over time. It’s a valuable addition for anyone seeking a dependable mid-level 8L90 transmission rebuild kit.

GM Filter

A genuine GM filter is included to ensure proper fluid flow and debris protection during and after the rebuild. Using the correct OE-spec filter helps maintain pressure balance and prolongs the life of the clutches, steels, and other internal components.

Frequently Asked Questions

What makes this Level 3 8L90 transmission rebuild kit different from other kits?

This Level 3 kit focuses on improved durability and shift quality without increasing clutch capacity, making it ideal for daily driving and moderate power upgrades. It includes premium Raybestos friction components, upgraded steels, and a billet input shaft for strength beyond stock.

Does this rebuild kit work as a shift kit as well?

Yes. While it’s not a standalone “shift kit,” the upgraded clutches, steels, and piston significantly improve shift feel and consistency. Many shops use this kit to fix common 8L90 shift issues such as shudder, flare, and unstable pressure.

Is this rebuild kit compatible with all 8L90 transmissions?

The 8L90 has multiple input shaft versions, so fitment depends on model year, spline style, and torque converter specifications. Verifying spline count and shaft type ensures the correct upgrade for your vehicle.

Does this kit include everything needed for a full overhaul?

Yes. It includes an overhaul kit with essential gaskets and seals, the GPZ® clutch module, steel pack, Hi-Per Blue® C1 piston, a billet input shaft, and a GM filter. Transmission fluid and specialty tools are the only additional items typically required.

Is the billet input shaft necessary for a stock or lightly modified vehicle?

While not mandatory, the billet 300M shaft adds significant strength and is a major reliability upgrade over the OEM unit. It helps prevent future failures, especially in vehicles that tow, run larger tires, or may receive tuning down the road.