Sturdy Built Trailer Spindle for 3,500 lb #84 Axle — Weld-On 1 3/4" Round with Brake Flange & Grease Fitting

Heavy-duty weld-on spindle engineered to restore or build a 3,500 lb #84 trailer axle with an integrated brake flange and greaseable fitting.

This new Sturdy Built spindle is a direct-replacement, weld-on unit sized for #84 bearing combination hubs and rated for 3,500 pounds. It features a 1 3/4" round butt end designed to be welded into axle tubing, accepts the standard 1 1/16" outer and 1 3/8" inner bearings, and includes an Accu Lube (EZ Lube) grease fitting for straightforward hub lubrication. The attached 4-bolt brake flange fits common 3,500 lb disc brake kits and 10" drum backing plates, making it suitable for both repair and custom axle fabrication projects.

How does this spindle fit my existing axle or hub setup?

The spindle is machined to the #84 hub profile and accepts a 1.72" seal-surface diameter, matching common 3,500 lb hub assemblies. It bolts or welds into axle tubing using the 1 3/4" round butt end and is drilled for cotter pin retention and a 1" flat washer. If you have existing hubs, use a 3,500 lb bearing kit; otherwise choose Sturdy Built galvanized hub kits designed for this spindle.

• Fits #84 bearing combination hubs (1 1/16" outer, 1 3/8" inner)
• 1.72" inner seal surface to match standard seals
• Weld-on 1 3/4" diameter butt end for axle tubing installation
• Drilled for cotter pin and 1" round flat washer retention

What braking systems will mount to the flange?

The manufactured 4-hole brake flange accepts most 3,500 lb five-lug disc brake converters and standard 10" drum backing plates used on trailers. That makes this spindle compatible with popular brake kits from brands like Deemaxx, Kodiak, or Tie Down Engineering. Verify bolt pattern alignment with your brake kit before installation.

• 4-hole flange suited for common 3,500 lb disc brake adapters
• Works with 10" drum backing plates where applicable
• Designed for standard five-lug hub conversions with adapters

How do I maintain bearings and grease with this spindle?

An Accu Lube grease zerk is installed on the spindle so you can relubricate hub bearings without disassembly. Attach a grease gun to the zerk and force fresh grease through the hub, pushing out old grease around bearings and seals. Routine greasing extends bearing life and helps prevent overheating under load.

• EZ Lube/Accu Lube fitting already installed for quick service
• Lubricate through the zerk—no hub teardown required
• Regular greasing recommended based on towing frequency and load

What are the spindle’s key dimensions and materials?

This spindle is fabricated from steel to withstand towing stresses and machined for precise bearing and seal fits. The weld-on butt end measures 1 3/4" diameter by 2 5/8" length, and the assembly is sized for the 44649 outer and 68149 inner bearing combination. The robust construction and accurate seal surface ensure reliable operation when properly installed and welded.

• 3500 lb rated steel #84 axle spindle construction
• Butt end: 1 3/4" diameter × 2 5/8" length for welding
• Bearing combo: 1 1/16" (44649) outer, 1 3/8" (68149) inner
• Seal surface inner diameter: 1.72"

Who this spindle is for: This Sturdy Built weld-on spindle is aimed at experienced DIYers, trailer mechanics, and fabricators who need to repair a damaged spindle or build a straight axle from scratch. It’s ideal when the axle tubing and surrounding structure are sound but the spindle is worn or broken, or when converting hubs and brakes to a standard 3,500 lb configuration. Professional welding and proper bearing installation are required for safe, long-lasting performance.