918-06978 54" Deck Spindle Assembly Fit for MTD Cub Cadet 618-06978 RZT-S54 RZT-L54 XT1-ST54 XT1-GT54 Craftsman T8400 G8400 Z6660 3 Pack

What It Is

This is a three-pack of OEM-grade deck spindle assemblies designed to replace worn spindles on 54-inch cutting decks. Each spindle houses the bearings and pulley that drive the blade; you need one per blade (three total for a 54" deck). It’s a direct fit for MTD/Cub Cadet zero-turn and lawn tractors, including models like the RZT-S54, RZT-L54, XT1-ST54, XT1-GT54, and Craftsman equivalents (T8400, G8400, Z6660).

Fitment & Compatibility

Before buying, confirm your deck is exactly 54 inches (measured blade tip to tip) and that your mower uses the MTD pattern. The OEM part number is 618-06978 (also cross-references 918-06978). This three-pack works on:

• Cub Cadet RZT-S54, RZT-L54, XT1-ST54, XT1-GT54
• Craftsman T8400, G8400, Z6660
• Any MTD-built 54" deck with the same spindle bolt pattern (three bolts per spindle, 3/8-16 threads, 2.5" center-to-center).

Check your old spindle’s pulley diameter (this replacement uses a 4.5" pulley) and shaft length (approx. 2.25" from housing to blade mount). If your deck has a different pulley size or offset, this won’t fit. Also verify the blade bolt is 5/8" (common on MTD 54" decks).

Key Things to Know

• Quality: These are OEM-spec replacements, not cheap aftermarket. Bearings are sealed and pre-lubricated; housing is cast iron. Expect 200–400 hours of life under normal residential use.
• Installation difficulty: Moderate. You’ll need a socket set, a breaker bar for stubborn bolts, and possibly a puller if the old spindle is seized. Plan 1–2 hours for all three.
• Common gotcha: The pulley nut is left-hand threaded on some MTD decks. Check yours before forcing. Also, replace the blade bolts if they’re worn—they’re cheap insurance.
• What’s included: Each spindle comes with the housing, bearings, shaft, and pulley. No blades, bolts, or spacers—reuse your old ones or buy separately.

Should You Buy It

If you own a 54" Cub Cadet or Craftsman with a failing spindle (wobbling blade, loud bearing noise, or uneven cut), this three-pack is the most cost-effective fix. At $65.89 for all three, it’s cheaper than buying singles and matches OEM quality. Avoid if your deck is not MTD-based or you need a different pulley size. Right for DIYers with basic mechanical skills.