618-06978 Spindle 918-06978 Assembly 54 inch Deck Fit for Cub Cadet RZT-L54 RZT-LX54 RZT-S54 ZT1-54 XT1-ST XT1-GT XT2-GX, for Troy-Bilt MustangXP Bronco TB2454, for Craftsman G8400 Z6900 Lawn Mower

What It Is

The 618-06978 spindle assembly (also listed as 918-06978) is the rotating hub that holds and drives the mower blade on 54-inch fabricated decks. It’s designed for heavy-duty residential and light commercial mowing on Cub Cadet, Troy-Bilt, and Craftsman zero-turn and lawn tractors with a 54-inch deck.

Fitment & Compatibility

• Deck size: Only fits 54-inch fabricated (not stamped) decks. Measure your deck width and check for a fabricated steel deck.
• Direct fit models: Cub Cadet RZT-L54, RZT-LX54, RZT-S54, ZT1-54, XT1-ST, XT1-GT, XT2-GX. Also fits Troy-Bilt Mustang XP, Bronco TB2454, and Craftsman G8400, Z6900.
• OEM cross-reference: Replaces Cub Cadet OEM 618-06978 and 918-06978. Aftermarket part, not genuine Cub Cadet.
• Physical check: Measure spindle shaft diameter (typically 1-inch) and bolt pattern (3-bolt, 4-inch spacing). Confirm mounting holes align with your deck before ordering.

Key Things to Know

• Quality note: Aftermarket part at a lower price than OEM. Some users report shorter bearing life than genuine Cub Cadet spindles under heavy use.
• Installation: Moderate difficulty—requires removing the blade, belt, and pulley. Use a puller if the old spindle is seized. Torque blade bolt to 50–60 ft-lbs.
• Common gotcha: The spindle may come without a grease fitting. If your deck has zerks, you’ll need to install one yourself or buy a pre-greased version.
• Check for damage: Inspect the deck housing for cracks or stripped bolt holes before installing. Damaged housing can cause premature spindle failure.

Should You Buy It

If you need a budget-friendly replacement for a single spindle on a 54-inch Cub Cadet, Troy-Bilt, or Craftsman mower and you’re comfortable with basic mechanical work, this is a solid value. It’s not ideal for daily commercial use or if you want OEM longevity—for that, spend more on a genuine Cub Cadet spindle.