Sun coast CAT3 700 HP CUSTOM ALLISON TRANSMISSION WITH CONVERTER (GMAX-CAT3-LB7-0103-4WD) for 2001-2004 Duramax LB7

This Sun Coast Allison transmission upgrade package includes several critical billet components designed to eliminate common weak points found in factory Allison transmissions. These upgrades improve durability, torque capacity, and long-term reliability for high-horsepower Duramax applications.

Built for trucks used in towing, performance builds, and competition environments, these components help the Allison transmission withstand the increased stress created by higher torque levels and aggressive driving conditions.

Billet Flexplate

The SunCoast billet flexplate replaces the factory stamped steel flexplate with a stronger one-piece billet steel design. This upgrade eliminates a known weak point found in many stock flexplates.

The flexplate connects the crankshaft to the torque converter and must withstand extreme torque loads. The Sun Coast billet flexplate is SFI 29.3 certified, meeting modern safety requirements for high-performance vehicles.

SFI certification is required in many racing applications. Vehicles running 11.99 seconds or faster in the quarter mile or exceeding 135 mph must use an SFI-certified flexplate.

Billet Allison Input Shaft

The Sun Coast billet input shaft addresses one of the most common failure points in the Allison transmission. The factory input shaft often fails under high torque loads.

Sun Coast manufactures this upgraded shaft using 9310 Vacumelt steel, which increases torsional fatigue strength by more than 50 percent. The shaft also features an increased radius at the turbine spline to improve strength.

This upgrade is highly recommended for trucks with larger tires, heavy towing setups, and performance modifications.

Triple Disc Torque Converter

Sun Coast manufactures its Allison 1000 torque converters in-house, allowing custom design and precise control over stall speed and torque multiplication.

The triple disc converter includes a forged billet steel cover and provides strong lock-up performance under heavy load. Each converter receives custom pump and turbine modifications for improved efficiency.

SunCoast also TIG welds each furnace-brazed fin for added reinforcement. The converter uses proprietary trapezoidal clutch teeth, which improve clutch engagement and durability.

Billet C2 Clutch Hub

The factory C2 clutch hub can fail under heavy loads or aggressive driving conditions. This failure often occurs in trucks with large tires, high horsepower tuning, or competition use.

Sun Coast replaces the factory hub with a billet C2 clutch hub manufactured from heat-treated 4140 steel. The spline length is increased by .125 inches to improve contact area. In addition, the spline boss diameter is increased by .100 inches for greater strength.

This upgraded hub is included in many 700-horsepower category transmissions.

Billet P2 Planetary Assembly

The P2 planetary gear set in the Allison transmission can fail when exposed to shock loads or high horsepower applications. Failure can result in catastrophic transmission damage.

Sun Coast manufactures the upgraded P2 planetary assembly using 4140 billet steel, which is induction hardened for strength and durability.

This upgrade is recommended for trucks used in sled pulling, drag racing, heavy towing, or other high torque applications.

New Internal Wiring Harness

Each Sun Coast Allison transmission build includes a new internal wiring harness. Over time, the factory harness connectors become brittle and may break during service.

Replacing the internal harness ensures proper electrical operation and improves overall transmission reliability.

Advanced Clutch and Hydraulic Improvements

SunCoast transmissions also include several proprietary upgrades designed to improve clutch durability and lubrication.

The transmission uses SunCoast proprietary C1, C2, C3, and C4 friction materials along with Alto Carbonite and Raybestos SCZ frictions. These frictions use a waffle pattern that helps retain oil for improved cooling.

Redesigned apply pistons use upgraded rubber compounds designed to handle higher temperatures. SunCoast also replaces the factory thin apply plate with a thicker spring apply plate to prevent distortion.

Additional fluid routing improvements allow lubrication to reach the entire clutch surface instead of only the center portion of the clutch pack.

Key Features

Billet SFI 29.3 certified flexplate for increased durability
9310 Vacumelt billet input shaft with increased torsional strength
Triple disc torque converter with billet steel cover
In-house custom pump and turbine converter modifications
Billet C2 clutch hub made from heat-treated 4140 steel
Induction hardened billet P2 planetary gear assembly
New internal wiring harness included in every transmission build
Upgraded Alto Carbonite and Raybestos SCZ friction materials
Redesigned apply pistons with improved heat-resistant compounds
Enhanced lubrication system for improved clutch cooling
Built to handle high horsepower, towing, and competition applications