SPOOLOGIC Unison Ring

The SPOOLOGIC Unison Ring SL-270-021 fits the GT3788VA turbocharger in 2004.5-2016 Chevrolet Silverado and GMC Sierra 2500 3500 6.6L Duramax. It links the VGT mechanism to the vanes for coordinated exhaust-flow control.

Features

• Replacement VGT unison ring
• Application-specific vane-pin slots
• For servicing a worn or damaged vane-control ring

What's Included

• 1 SPOOLOGIC Unison Ring

Fitment

• 2004.5-2005 Chevrolet Silverado GMC Sierra 2500 3500 6.6L Duramax LLY
• 2006 Chevrolet Silverado GMC Sierra 2500 3500 6.6L Duramax LLY
• 2006-2007 Chevrolet Silverado GMC Sierra 2500 3500 6.6L Duramax LBZ
• 2007.5-2010 Chevrolet Silverado GMC Sierra 2500 3500 6.6L Duramax LMM
• 2011-2016 Chevrolet Silverado GMC Sierra 2500 3500 6.6L Duramax LML
• 2006-2007 Chevrolet Express GMC Savana 2500 3500 6.6L Duramax LLY
• 2007.5-2008 Chevrolet Express GMC Savana 2500 3500 6.6L Duramax LMM
• 2009-2010 Chevrolet Express GMC Savana 2500 3500 4500 6.6L Duramax LMM
• 2010.5-2016 Chevrolet Express GMC Savana 2500 3500 4500 6.6L Duramax LGH

Turbo Compatibility

• Garrett variable-vane turbochargers

VGT Control System

The unison ring engages the vane pins so the vanes move together. Inspect the vane pins and ring contact surfaces during repair, and verify that the mechanism moves freely after assembly.

OEM Cross-References

• Garrett: 721913-0001, 721913-0003

⚠️ DIY Product — All Sales Final, No Warranty, No Returns

Every SPOOLOGIC Unison Ring is intended for experienced turbo builders and qualified technicians. Inspect the related VGT components for wear, binding, and damage; correct assembly and free movement are essential. All sales are final - no warranty, returns, or exchanges. Confirm compatibility before ordering. See the SPOOLOGIC Warranty Policy for details on parts sold without a warranty.