ALLISON A TRIM SOLENOID LB7/LLY 01-05

Allison A-Trim Pressure Control Solenoid

Part Number: 29533074

The Allison A-Trim Pressure Control Solenoid (29533074) is an OE-style replacement solenoid designed for 2001–2005 GM Duramax trucks equipped with Allison automatic transmissions. This solenoid installs in the valve body and plays a key role in regulating hydraulic pressure used for clutch apply control, helping the transmission maintain smooth, consistent shift quality under varying load conditions.

As solenoids age, internal wear and electrical issues can cause pressure control problems that show up as harsh shifts, delayed engagement, shift flare, or inconsistent shift feel. Replacing a weak or failing A-Trim solenoid helps restore proper hydraulic control and dependable drivability, especially during towing and daily-use situations where stable pressure control matters most.

Key Features and Benefits

• OE-style replacement for Allison A-Trim pressure control function
• Helps restore proper clutch apply pressure and shift consistency
• Designed to improve drivability by correcting pressure-related shift concerns
• Direct-fit valve body solenoid for service or rebuild work
• Ideal for preventative replacement during valve body service

Common Symptoms of a Weak or Failed A-Trim Solenoid

• Harsh or erratic shifting
• Delayed engagement into gear
• Shift flare or inconsistent shift timing
• Pressure control related drivability issues

Applications

• 2001–2004 Chevrolet Silverado 2500HD 6.6L Duramax LB7
• 2001–2004 Chevrolet Silverado 3500 6.6L Duramax LB7
• 2001–2004 GMC Sierra 2500HD 6.6L Duramax LB7
• 2001–2004 GMC Sierra 3500 6.6L Duramax LB7
• 2004.5–2005 Chevrolet Silverado 2500HD 6.6L Duramax LLY
• 2004.5–2005 Chevrolet Silverado 3500 6.6L Duramax LLY
• 2004.5–2005 GMC Sierra 2500HD 6.6L Duramax LLY
• 2004.5–2005 GMC Sierra 3500 6.6L Duramax LLY

Fitment notes: Verify transmission model and valve body configuration before ordering. This is intended for Allison-equipped LB7 and LLY Duramax applications within the model years listed.