TOYOTA 90171-16009 Ball Joint Castle Nut

Genuine Toyota OEM castle nut, part number 90171-16009. This specialized fastener is designed for critical points in the vehicle's suspension and steering systems, specifically for securing ball joint studs.

Functional Description and Significance

The castle nut, also known as a castellated or slotted nut, features distinctive slots (crown) at one end. Its design is essential for vehicle safety. It is used in conjunction with a cotter pin (split pin) inserted through the slots and a pre-drilled hole in the bolt or stud. This positive locking mechanism physically prevents the nut from loosening or backing off due to vibrations, road irregularities, and dynamic loads encountered during driving. For components such as ball joints, which connect the control arms to the steering knuckles, maintaining proper torque and preventing loosening is vital for safe and predictable vehicle handling.

Common Signs of Failure or Need for Replacement

Although the nut itself is a durable component, it should be inspected and replaced under certain conditions. Replacement is recommended if:

• The threads of the nut are damaged or stripped.
• The hex flats are rounded off due to improper tool usage, making proper torquing impossible.
• Significant corrosion is present that could compromise its structural integrity.
• The original nut is removed during maintenance or repair. Particularly for critical safety components, best practice requires installing a new fastener during reassembly to ensure correct clamping force and positive retention with a new cotter pin.

Technical Specifications

• Part Number: 90171-16009
• Brand: Toyota (Genuine OEM)
• Part Type: Castle Nut
• Material: High-tensile steel for strength and durability
• Surface Finish: Typically treated with a corrosion-resistant coating
• Application: Primarily for front and/or rear suspension ball joints

Vehicle Compatibility / Fitment

This part directly fits the following models:

• Toyota Land Cruiser 200 (VDJ200)
• Toyota Land Cruiser 200 (UZJ200)
• Toyota Land Cruiser 200 (URJ200)
• Toyota Land Cruiser 200 (GRJ200)

Note: Always verify compatibility using your vehicle's chassis number (VIN) prior to purchase.