Merchant Automotive Maximum Allison Transmission Work Series DIY Kit, LLY | 2004.5 - 2005

LLY Work Series Transmission Kit
Fits 2004.5–2005 GM LLY Duramax with Allison 1000 5-Speed

Give your 2004.5–2005 LLY Duramax the durability and performance it deserves with our Work Series Transmission Kit. Built on the proven Allison 1000 5-speed platform, this kit features upgraded clutch packs, enhanced hydraulic pressure, and reinforced internal components — all engineered to handle heavy workloads and increased power demands.

This kit is a great replacement for stock transmissions, delivering improved reliability and shift quality in daily-driven and unmodified trucks. It’s also perfectly suited for mildly upgraded builds, supporting added horsepower and torque with the right tuning and components.

Whether you’re towing, daily driving, or running performance upgrades, this is the same trusted configuration we use in our shop builds and real-world applications.

Kit Highlights

Direct fit for 2004.5–2005 LLY Duramax with Allison 1000 5-speed

Ideal for stock or mildly modified trucks

Increased clutch surface area for superior holding capacity

Heavy-duty C1–C5 frictions and steels

TransGo shift kit for improved shift quality and transmission longevity

Merchant Automotive deep pan with filter lock system

Includes all core bushings, bearings, gaskets, and valve body upgrades

Kit Contents

Transmission Internals

• Allison 5-Speed Overhaul Kit (2004.5–2005 LLY)
• T1 & T6 Bearings x2
• T2 Bearing
• T3–T5 Bearings x2
• T4 Bearing
• Front Pump Bushing
• Stator Support Bushing
• Transmission Adapter Gasket (Transfer Case to Transmission)
• C1 Valve Kit
• Pipe Thread Sealant Tape
• Allison Cut Back Valve
• Allison 1000 P1 Drive Flange

Clutch Packs

• C1 Frictions x6
• C2 Frictions x6
• C5 Frictions x6
• C3/C4 Frictions x9
• Alto Allison Piston Kit
• C1 Apply Plate x6
• C2 Steels x7
• C3/C4 Apply Pressure Plates
• C3/C4 Steels x7
• C5 Steels x6

Upgrades & Components

• Allison 1000 Deep Pan Kit w/ Merchant Automotive Deep Filter Lock
• PTO Billet Side Covers x2
• TransGo Shift Kit (5-Speed)
• Allison Pressure Switch Assembly
• Valve Body Kit
• Allison 1000 Pass-Through Connector Body & O-Ring
• F-Trim Sleeve
• Transmission Pressure Regulator Spring Tool
• Trim Springs “A” & “B”

Built for strength, tuned for performance — the Work Series Transmission Kit gives your LLY Duramax the strong foundation it needs to perform reliably under load, shift with confidence, and handle added power — whether you're stock, towing, or running light upgrades.