MK9578
Ball Joint
For SAAB 900
At a glance
- OE number
- MK9578
- Part
- Ball Joint
- Fitment
- 1967-1987 Saab 99 LOWER BOTH / 1978-1994 Saab 900 I LOWER BOTH / 1979-1993 Saab 900 I (Ac4, Am4) Front Lower Left And Right
- Supply
- Make to order / 1,000 pcs MOQ / 90–120 days
OE Cross-Reference
| OEM Brand | Reference Numbers |
|---|---|
| 555 SANKEI | |
| A.B.S. | |
| ABS | |
| ACKOJAP | |
| Ashika | |
| ASVA | |
| Beck/Arnley | |
| BIRTH | |
| Blue Print | |
| BLUE PRINT | |
| BORG & BECK | |
| CarParts | |
| DELPHI | |
| DORMAN | |
| FAI | |
| FCP Euro | |
| FeBest | |
| Febi | |
| febi bilstein | |
| FIRST LINE | |
| FVP | |
| GMB | |
| HERTH+BUSS | |
| JAPANPARTS | |
| JAPKO | |
| JIKIU | |
| JRAPP | |
| LYNXauto | |
| MASUMA | |
| Maxgear | |
| Mevotech | |
| MOOG | |
| NIPPARTS | |
| NK | |
| NTY | |
| OEM | |
| Optimal | |
| PATRON | |
| QH | |
| Riw | |
| Sidem | |
| SKF | |
| SLOOP | |
| Spareto | |
| SPIDAN | |
| STELLOX | |
| SUSPENSIA | |
| SWAG | |
| TALOSA | |
| TEKNOROT | |
| TOYOTA | |
| TOYOTA LEXUS | |
| Triscan | |
| TRW | |
| VEMA | |
| WILMINK GROUP | |
| SLOOP ← ours | MK9578SLSB-0260 |
Vehicle Fitment
About Ball Joints — function, symptoms & common questions
A ball joint is the spherical bearing that connects a suspension control arm to the steering knuckle — the pivot that lets the front wheel steer left and right while also moving up and down with the suspension. Modern independent front suspensions have one or two ball joints per side; ball joints are also used at some rear-suspension and 4×4 driveline locations.
Also known as: lower ball joint, upper ball joint, suspension ball joint, BJ.
How it works
Steering and suspension articulation
The ball-shaped stud rotates freely inside its socket, allowing the knuckle to swivel for steering input AND tilt vertically as the suspension compresses and extends — both motions through a single compact joint.
Load-bearing vs follower
On a standard control-arm/strut layout the lower ball joint is load-bearing (carries vehicle weight) and the upper joint, if present, is a follower (positions the knuckle but carries no vertical load). On a double-wishbone suspension both joints share the load.
Camber and caster anchoring
The two ball joints (or one ball joint plus the strut bearing) define the steering axis. Joint wear shifts that axis, throwing camber and caster out of spec.
Structure and construction
A hardened steel ball stud retained in a polymer (PTFE/POM) or metal-on-metal bearing inside a forged or pressed steel housing. Sealed with a neoprene/polyurethane boot and pre-greased for life on most modern designs (a handful of heavy-duty designs retain a grease zerk). Press-in or bolt-in mounting depending on control arm design.
Common failure symptoms
- Clunking over bumps. Worn bearing surface allows the ball stud to knock against its socket each time the suspension cycles.
- Steering pull or wander. The steering axis drifts as the worn joint allows the knuckle to shift, pulling the vehicle to one side under acceleration or braking.
- Cupped or feathered tire wear. Camber instability causes the contact patch to skip across the tire, creating uneven wear patches around the circumference.
- Visible play at the wheel. With the wheel off the ground, rocking the tire at the 12 and 6 o'clock positions reveals knocking — a definitive ball joint test.
Common questions about Ball Joints
Should I replace ball joints in pairs?
For load-bearing (lower) joints, yes — both sides see equal duty cycle and the second usually fails soon after the first. Upper (follower) joints can be replaced individually if only one shows wear.
Can I drive with a worn ball joint?
Not safely. Complete failure of a load-bearing ball joint causes the wheel to collapse outward — the vehicle drops onto the suspension and loses steering control. Replace immediately once play is detected.
Is alignment required after replacement?
Yes. Camber and caster are set by ball-joint position; replacement always shifts those values and a rack alignment is mandatory.
How long do ball joints last?
OEM joints typically last 120,000–250,000 km on paved roads. Off-road use, salt corrosion or boot damage shortens life dramatically.
Related Parts
FAQ
What vehicles use OE MK9578?
OE MK9578 fits Saab 99 (1967–1987), Saab 900 I (1978–1994), Saab 90 (1984–1987), Lexus Gs300 (1993–2020), Lexus Is250/300 (2000–2013), Toyota Crown Majesta (2003–2013) and 51 further model(s). Every confirmed make, model, year and fitting position is listed in the vehicle fitment table on this page.
Is this an original TOYOTA OEM part?
No. This is an aftermarket replacement manufactured by SLOOP, designed to meet OEM specifications. The OE number MK9578 is referenced under nominative fair use solely to identify vehicle compatibility — it does not imply licensing, endorsement, or affiliation with any vehicle manufacturer.
How do I confirm this part matches OE MK9578?
Form-fit-function tested against the OEM specification. Material test reports and dimensional drawings are sent with every quote. For high-volume orders we will produce a sample-grade pre-production unit for your QC team's verification before main run.
What certifications and quality standards do you carry?
ISO 9001:2015 quality management, plus REACH / RoHS for EU compliance. Material test reports and PPAP documentation are available on request for tier-1 buyers. Certificates ship with first shipment of every new SKU.
Do you offer samples?
No free samples. Your first order doubles as the qualification batch. We hold the production run until you confirm visual + dimensional inspection from the first carton. If anything is out of spec we re-make at our cost.
Payment terms?
100% T/T (bank wire) before production start. USD only. Bank details and proforma invoice are sent after you accept the quote. No credit terms, no Letters of Credit on first order.
Lead time and shipping?
Production: 90–120 days from confirmed payment. Sea freight 25–40 days from Taiwan port (most common). Air freight available on request for urgent orders. We can quote FOB Taiwan or DDP your warehouse.
What if I need a part you do not list?
Upload your full parts inquiry on the quote page. We match every line we carry and flag the rest for our manufacturing roadmap. Aggregated inquiries directly drive our next production batch.