Replacement 918-06978 Spindle Assembly for 54'' Deck, 618-06978 Lawn Mower Spindle Compatible with MTD Troy Bilt Cub Cad et RZT-L54 XT1 XT2, Craftsman G8400 T8400 Mower Deck Spindle

What It Is

This is a replacement spindle assembly (model 918-06978 / 618-06978) for the center or outer spindles on 54-inch cutting decks used on select MTD, Troy-Bilt, Cub Cadet, and Craftsman zero-turn and lawn tractors. It houses the bearing and pulley that drive the blade, and is a direct bolt-on replacement for a worn or failed OEM unit.

Fitment & Compatibility

Before buying, confirm these three things:

• Deck size & type: This spindle fits 54-inch fabricated or stamped decks only (not 42, 46, or 50-inch decks). Common models: Cub Cadet RZT-L54, XT1 Enduro Series, XT2; Troy-Bilt Mustang 54; Craftsman G8400, T8400.
• OEM cross-reference: Directly replaces OEM part # 918-06978 and 618-06978. If your spindle has a different number (e.g., 918-05116 or 718-06978), this will not fit.
• Measure before ordering: The spindle housing is roughly 6.5 inches tall with a 1-inch shaft diameter. The bolt pattern is 3-bolt (not 4-bolt). Measure your existing spindle height and bolt spacing—if they match, you’re good.

Key Things to Know

• Quality vs. OEM: This is an aftermarket unit. It uses sealed ball bearings (not serviceable). For heavy commercial use, OEM may last longer; for residential mowing, this is a solid value.
• Installation difficulty: Easy to moderate. You’ll need a socket set, wrenches, and a jack to lift the deck. Expect 30–60 minutes per spindle. No special tools required.
• Common gotcha: The pulley bolt may be reverse-threaded on some decks—check before forcing. Also, the spindle may come with a slightly different grease fitting location; it won’t affect function.
• Packaging: Some buyers report the spindle arrives without a blade or pulley—verify you’re reusing your old pulley and blade, or order separately.

Should You Buy It

Yes, if you have a 54-inch deck from an MTD/Cub Cadet/Craftsman residential mower and your spindle is noisy, wobbling, or seized. It’s a cost-effective, well-reviewed replacement that matches OEM specs for about half the price. Skip it if you need a spindle for a different deck size or a commercial-duty unit.