Mark Williams 40 spline lightweight steel spool for use with 9" Ford Rear End. Requires 3.250" bore case including the 57440 Mark Williams aluminum and 57470 Mark Williams nodular cases, and also requires 45mm wheel bearing (p/n 58505). Profile milling and cross-hole drilling saves 2-1/2 pounds over standard unit. Manufactured from through hardened 4140 high strength steel.

Instructions: SB0046

Features:

• Cut for 40 spline axles 
• 4140 Through hardened steel
• Uses 7/16 bolts
• Weighs 8.5 pounds
• Made in the USA

Note: We recommend replacing ring gear bolts every time a new gear is setup.