RZT-S54 Spindle Assembly 54" Deck 618-06978 918-06978 Fits for MTD Cub Cadet Troy Bilt XT1-ST54 XT1-GT54 ZT1-54 ST54 ZT2-54 TB2454 Craftsman T8400 G8400 Z6660（3 Pack）

What It Is

This is a replacement spindle assembly (3-pack) for 54-inch fabricated decks on select MTD/Cub Cadet/Troy-Bilt and Craftsman zero-turn and lawn tractors. It houses the bearings and pulley that spin the blade—critical for a clean, vibration-free cut on machines like the XT1-ST54, ZT1-54, and Craftsman T8400.

Fitment & Compatibility

Before buying, confirm three things:

• Deck size: Only fits 54-inch fabricated (not stamped) decks. Measure deck width and check for a flat, welded-steel underside.
• Model cross-reference: Fits Cub Cadet XT1-ST54, XT1-GT54, ZT1-54, ST54, ZT2-54, TB2454, and Craftsman T8400, G8400, Z6660. Also compatible with Troy-Bilt models using the same 54" deck.
• OEM numbers: Replaces OEM 618-06978 and 918-06978. Aftermarket part—verify your existing spindle has the same mounting bolt pattern (typically 3-bolt) and pulley diameter (approx. 4.5"). Measure center-to-center bolt spacing (roughly 3.5") and shaft length (approx. 2.75").

If your deck uses a different spindle (e.g., 46" or 50" decks, or stamped steel), this won’t fit.

Key Things to Know

• Quality: Aftermarket, not OEM. Most users report good durability, but bearings may wear faster than factory spindles under heavy commercial use. Inspect for smooth spin before install.
• Installation difficulty: Moderate. Requires removing the deck, belt, and pulley. You’ll need a socket set, a puller for the old spindle, and thread-locker on bolts. Expect 1–2 hours for all three.
• Common gotcha: The 3-pack saves money, but if only one spindle is bad, replace all three to avoid uneven wear. Also, check blade alignment after install—a bent spindle can cause vibration and poor cut.
• Warranty: Typically 90-day limited. No OEM support, so keep your old spindles as spares.

Should You Buy It

This 3-pack is a solid value for homeowners or light commercial users with the listed 54" MTD/Cub/Troy-Bilt/Craftsman decks who want to refresh all spindles at once. If you need exact OEM fitment or run a mower 40+ hours/week, pay more for genuine Cub Cadet spindles. For weekend warriors, it’s a cost-effective fix that works.