This genuine Allison gasket seals the rear housing to the transmission case on the Allison 1000 used in 2001 - 2019 Duramax Silverado and Sierra 2500HD/3500HD trucks. On 2WD trucks it seals the extension housing, and on 4WD trucks it seals the rear adapter housing that connects to the transfer case. GM lists it as the automatic transmission case extension housing gasket.

When this gasket hardens or is disturbed during rear housing, transfer case or transmission work, fluid can seep from the joint between the housing and the case. A new gasket reseals the joint.

Key Features

• Genuine Allison gasket, GM part number 29536941
• Seals the extension housing (2WD) or rear adapter housing (4WD) to the transmission case
• Approximately 14.4 Inch x 12.7 Inch, 0.036 Inch (0.91 mm) thick
• Fits the 5- and 6-speed Allison 1000 in 2001 - 2019 Duramax trucks

Benefits

• Stops fluid leaks between the rear housing and the transmission case
• Restores a proper seal after rear housing removal
• Correct factory fit and material

Frequently Asked Questions

Does this fit 2WD and 4WD trucks?

Yes. The same gasket seals the extension housing on 2WD trucks and the rear adapter housing on 4WD trucks.

Where exactly does this gasket go?

Between the rear housing and the back of the Allison 1000 transmission case. It is not the transfer case to adapter gasket. That's sold separately as the Transfer Case to Transmission Adapter Gasket.

Can I reuse the old gasket?

We don't recommend it. Once the rear housing has been removed, the old gasket won't reliably seal again.

When should I replace it?

Any time the extension or rear adapter housing comes off: replacing the housing, servicing the output shaft carrier bearing, or rebuilding the transmission.

Will this fit my 2020 or newer truck?

No. This gasket fits the 5- and 6-speed Allison 1000 used through 2019. 2020 and newer trucks use the Allison 10L1000 10-speed.

Fitment

• 2001 - 2019 Chevrolet Silverado 2500HD / 3500HD 6.6 Liter Duramax with Allison 1000, 2WD and 4WD (LB7, LLY, LBZ, LMM, LML, L5P)
• 2001 - 2019 GMC Sierra 2500HD / 3500HD 6.6 Liter Duramax with Allison 1000, 2WD and 4WD (LB7, LLY, LBZ, LMM, LML, L5P)
• Includes 2007 Classic and 3500HD cab and chassis

Replacing the rear housing? See the Allison Rear Adapter Housing for 2001 - 2010 4WD or 2011 - 2019 4WD, the Rear Adapter Housing Kit, and the Output Shaft Carrier Bearing. 2WD? See the Allison 2WD Rear Yoke Seal.

Prevent rear housing cracks with our Rear Housing Support for 2001 - 2007, 2007.5 - 2010 or 2011 - 2019.

What's Included

• (1) Genuine Allison extension / rear adapter housing gasket

For warranty information or to submit a claim, see our Warranty Form.

Details:

• Engine Manufacturer: Duramax
• Liter: 6.6 Liter
• Engine Designation: LB7, LLY, LBZ, LMM, LML, L5P
• Engine Years: 2001-2019
• Transmission Code: Allison 1000
• Location: Rear

Applications:

• 2001-2019 Silverado/Sierra 2500HD/3500HD LB7/LLY/LBZ/LMM/LML/L5P