918-06978 618-06978 Spindle Assembly for 54 Inch Mower Decks Cub Cadet RZT-S54 L54 ZT1-54 ZT2-54 XT1-ST54 GT54 XT2-54 GX54 Troy Bilt TB2454 Craftsman T8400 G8400 Z6660 (1-Pack)

What It Is

This spindle assembly (OEM part 918-06978 / 618-06978) is the rotating hub that holds the blade and pulley on 54-inch mower decks. It’s designed for residential and light-commercial zero-turn and lawn tractors from Cub Cadet, Troy Bilt, and Craftsman—specifically models with a stamped or fabricated 54-inch deck.

Fitment & Compatibility

Before buying, check three things:

1. Deck size: Only for 54-inch decks. Will not fit 42-, 46-, 48-, or 50-inch decks.
2. Model series: Fits Cub Cadet RZT-S54, L54, ZT1-54, ZT2-54, XT1-ST54, GT54, XT2-54, GX54; Troy Bilt TB2454; Craftsman T8400, G8400, Z6660. Also works on some RZT and Z-Force models with the same deck.
3. OEM vs aftermarket: This is an aftermarket replacement for OEM Cub Cadet part 918-06978 / 618-06978. It should be a direct swap, but measure the spindle shaft diameter (typically 5/8”) and pulley bolt pattern (usually 3-bolt) to confirm.

If your deck has a different spindle bolt pattern or shaft length, this won’t fit.

Key Things to Know

• Build quality: Aftermarket spindles vary. This one uses sealed bearings and a steel housing. Read recent reviews for bearing longevity—some report 1-2 seasons of use.
• Installation difficulty: Moderate. You’ll need a socket set, wrench, and possibly a puller to remove the old spindle. Expect 30–60 minutes per spindle.
• Common gotchas: The pulley may not be included (check product description). Also, the bolts that hold the spindle to the deck can seize—use penetrating oil and a breaker bar.
• One pack: This is a single spindle. You’ll need two or three for a full replacement, depending on your deck.

Should You Buy It

If you have a compatible 54-inch deck and your spindle is wobbling, making noise, or has a seized bearing, this is a solid budget-friendly replacement. It’s not heavy-duty commercial grade, but for residential use with standard mowing conditions, it’s a reliable fix at half the price of OEM.