54" Deck Spindle Assembly 618-06978 918-06978 Fits for Cub Cadet MTD Troy Bilt RZT-L54 RZT-S54, XT1-GT54 XT1-ST54, XT2 ST54, ZT1-54 ZT2-54 TB2454(Only fits 2019-2020), Z6600 T8400 G8400

What It Is

This is a 54-inch deck spindle assembly (model 618-06978 / 918-06978) that drives the mower blades on Cub Cadet, MTD, and Troy-Bilt zero-turn and lawn tractors. It’s a direct replacement for worn or failed spindles on 54” fabricated decks, commonly used in commercial and residential mowing.

Fitment & Compatibility

Before buying, check these three things:

• Deck size and type: Only fits 54” fabricated decks, not stamped or stamped-fabricated hybrids. Measure your deck width and look for a fabricated (welded) construction.
• Model and year: Fits Cub Cadet RZT-L54, RZT-S54, XT1-GT54, XT1-ST54, XT2-ST54, ZT1-54, ZT2-54, TB2454 (2019-2020 only), Z6600, T8400, G8400. Does not fit TB2454 models from 2021 or later.
• OEM vs aftermarket: This is an aftermarket part, not OEM Cub Cadet. It matches OEM #618-06978 and 918-06978. Confirm your old spindle’s bolt pattern (typically 3-bolt) and shaft diameter (usually 5/8”) to ensure compatibility.

Pro tip: Remove one spindle and compare the mounting holes and shaft length to the new unit before installing.

Key Things to Know

• Quality: Solid aftermarket build with sealed bearings. Most users report 1-2 seasons of heavy use. Not as durable as OEM Cub Cadet spindles, but fine for residential mowing.
• Installation difficulty: Moderate. Requires basic tools (ratchet, socket set, possibly a puller). Expect 30-60 minutes per spindle. You’ll need to remove the deck, belt, and pulley.
• Common gotchas: The pulley nut is often reverse-threaded (lefty-tighty, righty-loosey). Also, some units ship with dry bearings—add a dab of grease to the zerk fitting before use.
• Warranty: Usually 90 days to 1 year from third-party sellers. Check the listing details.

Should You Buy It

Right for homeowners or light commercial users who need a budget-friendly replacement for a single worn spindle on a 54” fabricated deck. Not ideal for heavy daily commercial use or exact OEM fitment—if you need maximum durability or have a 2021+ TB2454, stick with genuine Cub Cadet.