What Position Does K500123 Fit?
The K500123 installs at the:
- Front axle
- Passenger side
- Lower suspension position
It is a single ball joint, not a pair.
The corresponding driver-side part is generally:
- K500124 — front left lower ball joint
Do not substitute K500123 for K500124. The housings are side-specific, even if they look suspiciously similar while sitting on the workbench.
RWD Versus AWD Fitment
Drivetrain is the most important fitment qualification for this product.
On many covered Lexus models:
- K500123 fits the front-right lower position on RWD vehicles
- K500126 is associated with several AWD applications
- K500124 is the matching left-side RWD joint
The AWD suspension can use a different ball-joint housing and mounting arrangement. Model and year alone are not enough to confirm compatibility.
Before ordering, verify:
- RWD or AWD
- Passenger-side installation
- Original ball-joint housing shape
- Mounting-hole pattern
- Stud taper and thread
- OE number
- VIN and production date
Quick Specifications
| Specification | Detail |
|---|---|
| Brand | MOOG |
| Manufacturer | DRiV |
| Part number | K500123 |
| Part type | Suspension ball joint |
| Location | Front right lower |
| Quantity | One |
| Vehicle type | Select Lexus passenger cars |
| Primary fitment | RWD Lexus IS and GS models |
| Matching left side | K500124 |
| Installation type | Vehicle-specific replacement |
| Serviceability | Check included hardware and grease fitting |
| Warranty | Confirm current seller and MOOG terms |
What Does the Lower Ball Joint Do?
The lower ball joint connects the suspension arm assembly to the steering knuckle. It allows the knuckle to pivot as the wheels steer while also moving through normal suspension travel.
The joint helps maintain:
- Steering-knuckle position
- Suspension articulation
- Wheel alignment
- Predictable steering response
- Stable tire contact with the road
This component operates under braking, cornering and impact loads. A worn ball joint can let the wheel move outside its intended geometry, producing loose steering and uneven tire wear.
MOOG K500123 Construction
MOOG describes its Problem Solver ball joints as engineered for durability and controlled articulation. Depending on the current production version, design features may include:
- Hardened ball stud
- Powdered-metal bearing
- Lubrication channels
- Greaseable socket
- Protective dust boot
- Belleville-style preload washer
- Corrosion-resistant exterior surfaces
A greaseable design allows fresh lubricant to move through the bearing area and help flush contaminants from the joint. Check the actual package for a grease fitting and follow MOOG’s lubrication instructions. Do not assume that more grease is always better; an overfilled boot can be damaged or displaced.
Current retailer specifications for MOOG K500123 describe it as a vehicle-specific suspension ball joint backed by MOOG’s limited warranty terms.
Symptoms of a Bad Lexus Lower Ball Joint
A worn lower ball joint may cause:
- Clunking over bumps
- Popping during low-speed turns
- Wandering steering
- Loose or vague road feel
- Steering-wheel vibration
- Uneven front-tire wear
- Alignment instability
- Grease leaking from the boot
- Visible movement between the joint and knuckle
Our guide to diagnosing a clunking noise over bumps explains why ball joints, sway-bar links, control-arm bushings and strut mounts are often confused with one another.
If the noise occurs mainly while steering, review the Pro Street guide to clicking and popping noises while turning.
Inspect Before Replacing
A ball joint should be inspected using the procedure specified for that suspension. Some joints are checked with the suspension loaded, while others require the wheel or control arm to be unloaded.
Look for:
- Excessive radial or axial movement
- Torn dust boot
- Missing grease
- Corrosion around the housing
- Loose mounting hardware
- Damaged stud threads
- Elongated mounting holes
- Contact between suspension components
Do not replace a ball joint based solely on a clunk. A worn control-arm bushing, tie rod, wheel bearing or sway-bar link can produce nearly identical symptoms.
The Pro Street steering-wheel vibration guide covers additional tire, wheel, brake and suspension checks.
Should You Replace Both Sides?
Replacing both sides is usually sensible when:
- Both joints are original
- The vehicle has high mileage
- Both dust boots are deteriorated
- Play is present on both sides
- A complete suspension refresh is underway
- Labor overlap makes paired replacement practical
If only the passenger-side joint is damaged and the driver side passes inspection, replacing K500123 alone may be reasonable. However, the opposite side should still be inspected carefully.
For a matched repair, use:
- K500123 — front right lower
- K500124 — front left lower
Installation Considerations
Ball-joint replacement is an intermediate-to-advanced repair involving safety-critical suspension hardware.
Typical tools include:
- Floor jack
- Properly rated jack stands
- Wheel chocks
- Metric sockets and wrenches
- Breaker bar
- Torque wrench
- Ball-joint separator
- Pry bar
- Pliers
- Penetrating oil
- New cotter pin where specified
Use the factory-approved lift points and support the vehicle securely. Never work underneath a Lexus held up only by a hydraulic jack. Our guide on how to use an automotive jack safely covers the basic procedure.
During installation:
- Confirm K500123 is being installed on the passenger side.
- Compare the new housing with the original joint.
- Protect the ABS sensor wiring and brake hose.
- Inspect the steering-knuckle mounting surface.
- Use new locking hardware where required.
- Tighten all fasteners to the factory specification.
- Lubricate the joint only according to MOOG instructions.
- Check that the dust boot is seated and not pinched.
Do not use an impact wrench as a substitute for a torque wrench. “That feels tight” remains surprisingly absent from Lexus service literature.
Alignment After Ball-Joint Replacement
A professional alignment check is recommended after replacing a lower ball joint or disturbing connected suspension arms.
A correct alignment helps verify:
- Camber
- Caster
- Toe
- Steering-wheel position
- Straight-line tracking
- Tire-wear pattern
If the alignment cannot be brought into specification, inspect the control-arm bushings, upper joints, tie rods and steering knuckle.
For broader Lexus suspension planning, the Pro Street Energy Suspension guide explains how worn bushings contribute to unwanted suspension movement and inconsistent geometry.
Frequently Asked Questions
What vehicles does MOOG K500123 fit?
It fits the front-right lower position on select 2006–2020 Lexus IS and GS models, including the IS250, IS300, IS350, IS200t, IS F, GS300, GS350, GS430, GS450h and GS460. Drivetrain and model-year restrictions apply.
Does K500123 fit AWD Lexus models?
Generally, no. K500123 is primarily the right-side joint for RWD configurations. Several AWD applications use K500126 or another model-specific joint.
Does K500123 fit the left side?
No. K500123 is the passenger-side joint. K500124 is normally used on the driver side.
Does it fit the 2006–2015 Lexus IS250?
Yes, for RWD models. AWD versions require a different application.
Does it fit the 2006–2020 Lexus IS350?
It fits applicable RWD IS350 models. Verify the VIN for later model years because catalog coverage can vary.
Does it fit the Lexus IS F?
Yes. Listed coverage includes the 2008–2014 Lexus IS F.
Does it fit a 2007–2011 GS450h?
Yes, K500123 is cataloged for the front-right lower position on the 2007–2011 Lexus GS450h.
Is this a complete pair?
No. K500123 is one passenger-side ball joint. Order K500124 separately if both sides are being replaced.
Will it eliminate suspension clunking?
It can eliminate clunking caused by a worn right lower ball joint. It will not repair a bad control-arm bushing, sway-bar link, shock mount or tie rod.
Does the vehicle need an alignment afterward?
An alignment check is recommended after the repair, especially if connected suspension components were loosened or replaced.
Final Verdict
MOOG K500123 is a serviceable front-right lower ball joint for a broad group of Lexus performance sedans, but its fitment must be filtered by side and drivetrain. It is primarily intended for the passenger side of RWD applications.
Verify the VIN and original housing, pair it with K500124 when servicing both sides, install it using the correct torque procedure and finish with an alignment inspection.
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