The SPOOLOGIC Upgraded Compressor Housing Kit 68mm Billet Wheel SL-230-037 pairs a 68mm 11-blade billet compressor wheel with a matched compressor housing for the GT3788VA turbocharger on 2004.5-2007 6.6L LLY / LBZ Duramax applications. Sold as a matched kit so the wheel, housing, backing plate, and sealing hardware all work together — a drop-in upgrade for a tired stock cast wheel or a clean rebuild on a turbo that is coming apart for service. CNC-machined wheel: 68mm inducer, 88mm exducer base, 91mm extended-tip outer diameter, 11-blade.

Why Extended-Tip Exducer

Extended-tip technology lets a smaller wheel perform like a larger one. The blade tips extend past the back face of the exducer, increasing effective blade area without enlarging the inducer or compressor housing. Benefits versus a flat-tip wheel of the same base dimension:

• Greater airflow at the same shaft speed (more CFM per RPM)
• Faster boost response at lower engine speeds
• Higher peak pressure ratio and broader compressor map width
• Lower EGTs at cruise and under load from more efficient compression
• Improved high-RPM efficiency without losing low-end response

Why Billet Over Cast

• Forged aluminum billet has 15-25% higher yield strength than cast aluminum, allowing aggressive blade and tip geometry that would fail in cast form
• Thinner, more refined blade profiles reduce rotational mass for quicker spool-up
• Denser, aligned grain structure resists crack initiation and high-cycle fatigue
• Better foreign-object-damage tolerance — small debris nicks rather than fractures
• Higher safe tip speed allows the wheel to live behind aggressive tunes and added fueling

Drop-In Upgrade for Stock Turbos

The factory GT3788VA on the LLY and LBZ Duramax uses a 63mm cast wheel. Stepping up to a 68mm billet wheel adds inducer area for more airflow at higher RPM while staying inside the stock VGT housing envelope. The result is more usable top-end boost without sacrificing the low-end response that makes the variable-geometry turbo work in the first place. Billet construction takes the boost and heat without the stress cracking that ends cast wheel life. This kit ships the matched compressor housing pre-machined for the larger wheel — bolt-on, no cover clearancing required.

What’s Included

• (1) 68mm 11-blade billet compressor wheel
• (1) Compressor housing
• (1) Backing plate
• (1) Compressor wheel lock nut
• Sealing O-rings — set
• Mounting bolts — set

Wheel Specs

• Inducer: 68mm
• Exducer: 88mm base diameter, 91mm extended-tip outer diameter
• Blade configuration: 11-blade (11 full blades, no splitters)
• Material: 5-axis CNC-machined forged billet aluminum
• Profile: Extended-tip geometry
• Thread: Left-hand (turns left to tighten against turbo rotation)
• Balance: Computer-balanced from the factory

Installation Procedure

This kit installs as a complete wheel and compressor housing swap on the GT3788VA CHRA. The shaft nut is left-hand thread.

1. Remove the turbo from the truck
2. Remove the original compressor housing from the CHRA
3. Hold the turbine wheel hub against rotation with a leather glove or soft-jaw method — never use an impact gun
4. Remove the factory compressor nut by turning it clockwise (left-hand thread) and pull the original wheel off the shaft
5. Inspect the shaft and threads for damage; clean thoroughly with brake cleaner
6. Slide the new SPOOLOGIC billet wheel onto the shaft, oriented with blades facing the inlet
7. Apply a small drop of blue threadlocker to the shaft threads
8. Thread the supplied lock nut on by turning counter-clockwise (left-hand thread) and torque to 10 ft-lb / 120 in-lb
9. Install the supplied backing plate onto the CHRA using new sealing O-rings
10. Install the supplied compressor housing onto the backing plate
11. Install and torque the supplied mounting bolts to OEM spec
12. Verify the wheel spins freely with no rub against the compressor housing before reinstalling on the truck

Features

• Complete wheel-plus-housing upgrade kit for 2004.5-2007 6.6L LLY / LBZ Duramax
• 68mm inducer × 88mm exducer base with 91mm extended-tip outer diameter
• 11-blade (11 full blades, no splitters) blade configuration for broad compressor map width
• Matched compressor housing included for a clean wheel-to-housing fit
• Backing plate, sealing O-rings, lock nut, and mounting bolts all included
• CNC-machined wheel from forged 2618-class aluminum billet, computer-balanced
• Higher airflow and faster spool than the OE cast wheel
• Bolt-on upgrade — no shaft or housing machining required

Fits 2004.5-2007 6.6L Duramax LLY LBZ

• 2004.5 – 2007 Chevrolet Silverado GMC Sierra 2500 / 3500 6.6L Duramax LLY LBZ

Replaces Factory OEM Part Numbers

• Garrett: 773540-5001S, 773542-5001S
• GM: 97387896
• GM: 98011735

⚠ Not For Sale In California

Emissions Notice: Not CARB approved. Not legal for sale or use in the state of California.

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

This SPOOLOGIC compressor housing kit is a professional DIY assembly product intended for experienced turbo builders and rebuild shops. Successful installation requires proper tools, OEM service procedures, cleanliness standards, correct left-hand shaft nut torque to 10 ft-lb / 120 in-lb, and verification that the compressor wheel spins freely with no housing contact before running the turbo. Because SPOOLOGIC cannot control installation quality, all sales are final — no warranty, no returns, no exchanges. By purchasing this product you acknowledge that you are responsible for correct installation, torque, clearance verification, and assembly.