Audi A4 B8 Front Suspension Control Arms: OE Numbers and Replacement Guide

The Audi A4 B8 (2007–2015, platform codes 8K/8R) uses a five-link front suspension in which every corner is located by two lower links, two upper links and a steering tie rod. Those links carry all braking, cornering and bump loads through rubber bushings and ball joints, and they are the parts that wear first — typically showing signs around 70,000 miles (about 112,000 km) of mixed driving, with clunks, steering play and vibration as the early warnings [1]. This guide gives a straight OE cross-reference for the B8 front control arms (forward lower, rearward lower and upper links), explains the symptoms that mean replacement, and lists the torque and installation points that determine whether the new arms last.

Quick reference: B8 front control arm OE numbers

The table below maps each suspension position to its factory Audi part number. “Hetian No.” is the in-house part reference used by Hetian Auto Industry; always cross-check the factory OE number against the casting or sticker on your old arm before ordering, because B8 production spans two generations of ball-joint and bushing designs (M12/M14 ball joint taper changed through the run) [5].

Why the B8 five-link front suspension wears out

On the B8 each front corner uses two lower links — a forward arm and a rearward arm — plus two upper links, each fixed to the subframe with a rubber bushing and to the wheel carrier with a ball joint [5]. The forward bushing absorbs most of the braking compliance; the rearward link carries more cornering load [7]. When the bushings tear, the arm gains play under load, wheel geometry (camber and toe) shifts measurably, and the front end starts to clunk and wander [7].

The B8 is also fitted with aluminium arms on many trims and on the Quattro, and the forward lower arm ball joints are separate service items rather than riveted-in, which changes how the front end fails and how it should be diagnosed [1][5]. Ball joints commonly reach the end of their service life before the arm casting itself; the rubber bushings harden, crack and separate from the sleeve as the car passes roughly 70,000 miles, which is why B8 front-end overhaul kits sell so widely at that mileage point [1][6].

Part by part: what each B8 front arm does

Forward lower control arm (8K0407151 / 8K0407152)

The forward lower link runs from the front of the subframe to the bottom of the steering knuckle. Audi lists it as “Front Lower Control Arm,” position right lower / left lower, and the factory part is supplied with bushings installed [4]. It is the arm that visibly twists under braking, and the first one to knock when its inner bushing tears [1][4]. The OE numbers 8K0407151G/F (left) and 8K0407152G/F (right) correspond to the current factory revision that superseded the earlier -B/-C/-D suffixes [4].

Rearward lower control arm (8K0407693 / 8K0407694)

The rearward lower link connects the rear subframe mount to the knuckle and carries the larger share of cornering and lateral load. Audi’s catalogue describes the equivalent part (8K0407693AF) as “Lower Link – Incl. Ball Joint & Bushings”, confirming that the rearward arm is normally serviced as a complete assembly rather than rebuilt [5]. In the aftermarket the 8K0407693/8K0407694 family is the most frequently replaced B8 front arm because its rear bushing takes the heaviest continuous load [7].

Upper control arms (8K0407505 / 8K0407506 / 8K0407509 / 8K0407510)

The two upper links locate the top of the wheel carrier and set camber. Their bushings are exposed to the same heat, salt and debris as the lower arms, and on the B8 they wear in step with the lower set — which is why shops quote the front end as a full set of four to six arms once the first one fails [1]. If an upper link bushing has failed, the alignment will not hold and the car will pull under braking, even though the arm itself looks straight [7].

Symptoms that mean the arms need replacing

• Dull clunk or knock from one front corner over speed bumps, expansion joints and driveway transitions — the classic first sign of bushing wear [7].
• Steering free play and a vague, woolly feel at speed; the car drifts in ruts and needs constant small corrections [1].
• Vibration through the steering wheel, particularly as a ball joint approaches failure — replace immediately in this case [1].
• Pull under braking and uneven front tyre shoulder wear — the geometry is shifting because a bushing has torn [7].
• Visible damage: cracked or separated rubber bushings, torn ball joint boots, grease weeping from a joint [1][2].

On a lift, grab the tyre at 12 and 6 o’clock and rock it — vertical movement or a clunk points to ball joint play; then check each bushing with a pry bar against the subframe. Movement of about 3 mm or any knock means the bushing is done [1][2]. Ball joints and bushings are typically worn by around 70,000 miles; start inspecting the front end at every service from that point on [1].

Replacement essentials: pairs, pre-load and torque

Control arms are installed in pairs on an axle, and both sides should be renewed together because wear is symmetric [2]. The single most common installation mistake is tightening the bushing bolts while the suspension is hanging — the rubber twists as soon as the car sits down and tears itself apart [2]. The correct sequence is to fit everything finger-tight, lower the car so the suspension is compressed to ride height, then torque the bolts to the factory values [2].

Representative B8 front-arm torque figures from the FCP Euro guide: 16 mm control arm bushing bolts 50 Nm + 90°, the 14 mm pinch bolt 40 Nm, the front lower forward ball joint 110 Nm, and the rearward lower ball joint nut 145 Nm; wheel lugs 120 Nm [1][3]. Always confirm against the current factory data for your exact build date, because the ball-joint taper changed part-way through B8 production [5]. After any control arm work, a four-wheel alignment is mandatory — control arm replacement changes camber and caster [2][7].

How to choose replacement arms for the B8

Match the factory OE number on the old arm first, including the suffix — a B8 lower arm is not interchangeable between front- and all-wheel-drive layouts, and the ball-joint taper differs across build dates [5]. Prefer complete assemblies (arm + bushings + ball joint) over pressing new bushings into old castings; a worn arm casting cannot be restored reliably [2][5]. When buying aftermarket, verify the supplier rather than the price: production under IATF 16949, an in-house laboratory (for example CNAS-accredited testing), and consistent export quality across 30+ countries are the checks Hetian applies to its own chassis parts line. A 5–10 minute fitment check against the old arm (hole spacing, bushing style, ball-joint taper) before installation prevents the most common comebacks [5].

FAQ

Q1. How many control arms does an Audi A4 B8 have in the front?

Four per corner: two lower links (forward and rearward) and two upper links, plus a steering tie rod — eight arms in total across the front axle on the five-link design [5][7].

Q2. What is the typical lifespan of B8 front control arms?

Bushings and ball joints are usually well worn around 70,000 miles (about 112,000 km), with harder use (city traffic, poor roads, heavy loads) bringing the failure forward [1].

Q3. Can I replace just one arm instead of the whole set?

The failed corner must be fixed, but arms are fitted in pairs and wear is symmetric; renewing one side only leaves the opposite side to fail shortly after, so shops normally quote both sides [2].

Q4. Are the forward and rearward lower arms the same part on the B8?

No. The forward arm is 8K0407151/8K0407152 family and the rearward arm is 8K0407693/8K0407694 family; they have different bushings, ball joints and mount geometry, and each is left/right specific [4][5].

Q5. Do I need a wheel alignment after replacing control arms?

Yes — control arm work changes camber and caster, and skipping the alignment causes pulling, off-centre steering and uneven tyre wear [2][7].

Q6. Why does my B8 clunk only over speed bumps, not on smooth roads?

A worn bushing only knocks when the suspension loads and unloads quickly — speed bumps and expansion joints do exactly that. If the noise also appears at constant speed on smooth pavement, the cause is more likely wheel bearings, dampers or stabilizer links [7].

Related Guides

• Chassis noise diagnosis: how to identify worn control arms, ball joints, bushings and links by sound
• Aftermarket control arm quality: a supplier verification checklist for chassis parts buyers
• Suspension parts fitment check: how to verify control arms and links before installation
• Ball joint boot cracked: dust boot damage inspection and replacement guide
• Control arms product category

References

[1] How To Replace Audi B8 A4 Front Control Arms (A5 & Q5), FCP Euro, 2021-03-10, https://www.fcpeuro.com/blog/how-to-replace-front-control-arms-audi-b8-a4-a5-q5, accessed 2026-11-04

[2] Replacing Control Arms, ZF Aftermarket, https://aftermarket.zf.com/en/aftermarket-portal/for-workshops/useful-tips/suspension/replacing-control-arms/, accessed 2026-11-04

[3] How to change front lower arm on AUDI A4 Avant (8K5, B8) – replacement guide, AUTODOC CLUB, https://club.autodoc.co.uk/manuals/how-to-change-front-lower-arm-on-audi-a4-avant-8k5-b8-replacement-guide-25982, accessed 2026-11-04

[4] Audi Genuine Lower Control Arm Suspension Control Arm 8K0407152D, Audi OEM Parts, https://www.audioemparts.com/oem-parts/audi-genuine-audi-lower-control-arm-suspension-control-arm-8k0407152d-oem-8k0407152d, accessed 2026-11-04

[5] Suspension Components for 2011 Audi A4 Quattro, Audi OEM Parts Online, https://audi.oempartsonline.com/v-2011-audi-a4-quattro–avant–2-0l-l4-gas/suspension–suspension-components, accessed 2026-11-04

[6] Audi A4 B8 front control arm set: selection, replacement, prices, Audi Insight, https://audiinsight.cc/articles/k/ko/komplekt-perednikh-rychagov-audi-a4-b8.html, accessed 2026-11-04

[7] Audi Control Arm Failure: Symptoms, Diagnosis & What to Do, Motronix, https://motronix.net/blog/audi-control-arm-failure-symptoms-diagnosis/, accessed 2026-11-04