3 Pack 618-04125A Mower Spindle Assembly RZT 50 in Deck for MTD Cub Cadet Mustang Zero Turn 50" Mower Deck LT1050 LGTX1050 RZT50 918-04125B 918-04126 618-04126 918-04125 618-04125

What It Is

This is a 3-pack of replacement spindle assemblies for 50-inch zero-turn and lawn tractor decks. Each spindle houses the bearings and pulley that spin your mower blades; they’re direct replacements for worn or damaged spindles on Cub Cadet and MTD machines with a 50" fabricated deck, including the RZT 50 and LT/LGTX1050 series.

Fitment & Compatibility

Before buying, confirm three things:

1. Deck size and type – This fits only 50-inch fabricated (not stamped) decks. Common models: Cub Cadet RZT 50, LT1050, LGTX1050, and Mustang ZT 50. It will not work on 42" or 54" decks.
2. OEM cross-reference – Replaces OEM numbers 618-04125A, 618-04125, 618-04126, 918-04125B, 918-04125, and 918-04126. If your spindle has a different number, measure the bolt pattern (typically 3-bolt, 3.5" center-to-center) and shaft diameter (usually 5/8" or 3/4").
3. Pulley and blade fit – The spindle comes with a pressed-on pulley (likely 4.5" OD). If your belt uses a different pulley size or you need a top-mount pulley, you’ll need to swap it. Also verify blade hole size (commonly 5/8" or 7/8").

Key Things to Know

• Quality vs OEM – These are aftermarket spindles. Most buyers report good longevity, but some note the bearings aren’t as grease-sealed as genuine Cub Cadet parts. Expect 1–2 seasons under heavy use.
• Installation difficulty – Moderate. You’ll need a socket set, a jack to lift the deck, and a puller to remove the old pulley if it’s rusted. Budget 1–2 hours for all three.
• Common gotcha – The mounting bolts are often 5/16" or 3/8" hex; check your deck’s bolt size before starting. Also, the spindle shaft may be slightly shorter than OEM—verify blade clearance if your deck uses thick blades.
• Bearing noise – A few buyers report slight noise after 50 hours. If you mow commercially, consider greasing the bearings manually (if zerk fittings are present) or upgrading to sealed OEM units.

Should You Buy It

If you have a 50" Cub Cadet or MTD zero-turn or lawn tractor with a fabricated deck and want a cost-effective, drop-in replacement without the OEM price premium, this 3-pack is a solid choice. It’s best for homeowners who mow a moderate-size lawn and are comfortable with basic mechanical work. Not recommended for heavy commercial use or if you need exact OEM tolerances.