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Drivetrain› Manual Transmissions and Components

Sonnax

Heavy Duty Output Shaft

$995.00 $790.45 Save $204.55

SKU: 74678S-HD

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In Stock
Ships by Aug 5
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30 Days Return
INSTALL DIFFICULTY
DIY PRO SHOP

Moderate — 2–4 hours

Description

The Sonnax heavy duty output shaft (74678S-HD) addresses common output shaft failures experienced in GM 4L60-E, 4L65-E, and 4L70-E transmissions, particularly as power levels are increased. Constructed from high-strength 300M steel, the shaft boasts rolled splines for increased durability. It undergoes specialized heat treatment and processing to ensure maximum toughness and longevity under stress. This combination of materials and advanced manufacturing techniques makes it a robust upgrade for performance-oriented GM transmissions.

MIA's Description

The Sonnax heavy duty output shaft is precision engineered and manufactured for unbeatable performance in high-horsepower street and strip builds. This shaft is designed for 4WD/AWD units and features a torsional design that absorbs energy, reducing peak loads to critical areas. It is constructed from high-strength 300M steel with rolled splines and is specially heat-treated for maximum toughness.

Fitment

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Specifications

BrandSonnax
Part Number74678S-HD
CategoryDrivetrain

Buy with Confidence

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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