618-06978 918-06978 Spindle Assembly for 54" Mower Deck Cub Cadet RZT-L54 RZT-S54 ZT1-54 XT1-GT54, Troy Bilt TB2454 Mustang 54 XP, MTD Craftsman Z6900 Z6600 T310 G8600 G8400, with Nut (3 Pack)

What It Is

This is a replacement spindle assembly (3-pack) for 54-inch mower decks on select Cub Cadet, Troy-Bilt, MTD, and Craftsman zero-turn and lawn tractors. It drives the mower blade and houses the bearings that allow the blade to spin freely.

Fitment & Compatibility

Before buying, verify these three things:

1. Deck size – Fits only 54-inch decks. Measure your deck or check the model number (e.g., RZT-L54, ZT1-54, XT1-GT54, Mustang 54 XP, Z6900, Z6600, T310, G8600, G8400).
2. OEM cross-reference – Replaces OEM part numbers 618-06978 and 918-06978. If your original spindle has a different number, measure the bolt pattern (center-to-center) and shaft diameter.
3. Physical dimensions – Typically 4.5-inch bolt pattern, 1-inch diameter shaft, and 3.5-inch housing height. Measure your old spindle to confirm.

Key Things to Know

• Quality – Aftermarket part, not OEM. Most buyers report it works well but check for smooth bearing rotation before installing.
• Installation – Moderate difficulty. You’ll need a jack, socket set, and possibly a puller if the old spindle is seized. Plan 1–2 hours for all three.
• Common gotcha – The included nut may be SAE thread; verify your blade bolt thread pitch before tightening. Use thread locker.
• Bearing life – Grease fittings are not present on this assembly. Expect 2–3 seasons of residential use before bearing wear.

Should You Buy It

If you have one of the listed 54-inch Cub Cadet, Troy-Bilt, MTD, or Craftsman mowers and need to replace a worn or noisy spindle, this 3-pack offers good value. It’s a solid aftermarket alternative to OEM parts for residential users, but commercial operators should consider OEM for longer bearing life.