Allison 1000 Rear Output Shaft Nut, Duramax | 2001 - 2010

Allison 1000 Rear Output Shaft Nut - 2001-2010 GM 6.6L Duramax LB7/LLY/LBZ/LMM - 29531231

The Allison 1000 Rear Output Shaft Nut is a GM replacement locking nut designed to secure the rear output shaft in Allison 1000 automatic transmissions found in 2001-2010 GM 6.6L Duramax diesel trucks. This nut must be removed when servicing the rear output shaft, replacing bushings or bearings, removing the rear adapter housing, or rebuilding the transmission. Because it features a locking design, replacing the nut rather than reusing the original is recommended whenever it has been removed.

Important Availability Notice: GM Part Number 29531231 has been discontinued by General Motors. Remaining inventory is limited, and availability may be exhausted once existing stock is sold. Contact Merchant Automotive for assistance identifying an alternative if this part is no longer available.

Key Features

• GM replacement rear output shaft retaining nut for Allison 1000 automatic transmissions.
• GM Part Number: 29531231.
• Locking-style nut designed to secure the transmission output shaft.
• Used during output shaft replacement, rear transmission service, and transmission rebuilding.
• Suitable for installation when upgrading to a billet output shaft.
• Designed for Allison 1000 transmissions in Duramax LB7, LLY, LBZ, and LMM applications.
• Discontinued by GM with limited remaining inventory.

Benefits

The rear output shaft nut is an important retaining component within the Allison 1000 transmission. During transmission rebuilding, output shaft upgrades, rear bushing replacement, or adapter housing removal, the original nut must be removed to access the necessary components. Installing a new locking nut helps maintain proper output shaft retention without relying on a previously used locking fastener. Replacing this component during transmission service is especially important when installing upgraded drivetrain components or completing a full transmission rebuild.

Fitment

2001-2010 Chevrolet Silverado and GMC Sierra 2500 HD and 3500 equipped with the 6.6L Duramax diesel engine and Allison 1000 automatic transmission, including LB7, LLY, LBZ, and LMM engine generations.

Fitment Note: This nut is intended for 2001-2010 Allison 1000 transmissions. Trucks equipped with 2011-2019 Allison 1000 transmissions require the corresponding later-style rear output shaft nut.

What's Included

• (1) Allison 1000 Rear Output Shaft Nut - GM Part Number 29531231.

Installation Notes

The Allison 1000 Transmission Output Shaft Nut Tool for 2001-2010 applications is required for removal and installation of this retaining nut. The tool is sold separately. Replace the locking nut whenever it is removed during transmission service.