Control arm replacement and steering knuckle removal -B5 Passat and Audi

Dec 7, 2013
Control arm replacement and steering knuckle removal -B5 Passat and Audi
  • Control arm replacement and steering knuckle removal on VW Passat
    difficulty: 2/5back to 1000q: B5.5 VW Passat TDI "how to" index

    Introduction

    The control arms wear out and replacement will refresh the suspension on your VW Passat TDI. This article will also work on Audi A4 and A6.
    Early Audi A4/Passat front control arms had some wear and sway bar link problems. Most of these problems were fixed in the TDI since they were only available in the last 2 years of the B5 body Passat, 2004 and 2005. While the multilink front suspension gives the Passat good steering feel and handling sophistication, it's also complicated and expensive. There are 4 ball joints per side and although the control arms are aluminum, it's still heavier than a cheap stamped steel lower control arm with a McPherson strut.

    The reason there are 4 ball joints (2 upper, 2 lower per side) is because this creates a virtual steering axis. Steering axis is an imaginary line between the top and bottom of where the wheel on your car rotates (illustrated below). On a McPherson strut suspension, the axis rotates at the top of the strut and at the bottom at the single ball joint. Below is a highly simplified 3-d illustration comparing a strut vs. virtual multilink. The red dots represent the top/bottom of the steering axis. The blue is the suspension upright. In a McPherson strut, the strut itself is the upright.

    In the McPherson strut, the steering axis or rotation point is limited by the physical length of the lower control arm and follows the strut up. By using multiple ball joints, your Passat or Audi creates a virtual steering axis (dotted black lines below) that's not physically possible with a single control arm since it would have to extend to where the tire/wheel is.
    [​IMG][​IMG]
    This changes the scrub radius, the distance between the steering axis and center of the tire contact patch. The advantage is better steering feel and more flexibility over a traditional wishbone suspension. The major problem is that more parts mean more things can wear out. And unlike some wishbone suspensions, you can't shim the control arms.

    The basic front suspension layout is identical to an Audi A4 (used since 1994 so there were some changes to the control arms over the years) but the rear is different. All Passat TDI use a torsion beam rear axle instead of the independent rear suspension on the Audi. Even Passat w/4motion (all wheel drive, not available in North American with the TDI engine) use a different independent rear suspension from the Audi. It's not possible to convert your VW Passat TDI to 4motion AWD because the floorpan and transmission are different.

    Failing control arms typically sound like groaning or creaking when braking. Loose wandering steering on the highway is also a symptom of worn control arm bushings.

    To access the rear control arm bolt, you have to slightly lower the subframe. The bolts are single use stretch bolts! Some reuse the subframe bolts and their cars haven't fallen apart but I would not reuse them more than once. My car got all new bolts. See 1000q: torque wrench FAQ - stretch bolts to see why you shouldn't reuse them.

    Steering knuckle removal
    The control arms must be disconnected from the steering knuckle during removal so this article also shows how to remove the steering knuckle completely. I do not suggest removing it if you're just replacing the control arms because you have to remove the driveaxle bolt (see 1000q: CV boot replacement for more details, the bolt is a single use stretch bolt!), brake line, and ABS sensor wire. Unless you have a VCDS cable to actuate the ABS pump to get trapped air out of the brake lines, do not disconnect the brake lines! See 1000q: brake fluid bleed for more details. To loosen the axle bolt the car must be resting on the ground so do that first if you intend to remove the driveaxle or steering knuckle!

    Parts
    PB Blaster, liquid wrench, or another penetrating lubricant
    13, 16 mm sockets
    torque wrench

    hardware:

    you can buy a partial kit from ecstuning, add the tie rod hardware separately
    (1 per side) upper control arm pinch nut VW# n 102 861 10
    (1 per side) tie rod end pinch nut VW# n 102 861 10 (same as above)
    (1 per side) tie rod end pinch bolt VW# 4d0 407 192 c
    (1 per side) upper control arm pinch bolt VW# (unknown)
    (1 per side) vertical tie rod end lockbolt VW# n 034 790 8
    (2 per side) sway bar endlink bolts VW# n 104 253 01
    (1 per side) lower rear control arm bolt VW# n 906 259 02
    (1 per side) lower front control arm bolt VW# n 102 949 01
    (2 per side) upper control arm bolt (2 per side) VW# n 104 253 01

    control arms
    left sway bar endlink (optional, marked with blue dot) VW# 8d0 311 317 d
    right sway bar endlink (optional, marked with yellow dot) VW# 8d0 311 318 d

    I suggest a kit if you're replacing control arms - available from ecs tuning, mjmautohaus

    Subframe bolts
    Note
    - the long 18m subframe bolts are single use stretch bolts!
    (4 total) front and rear subframe long 18mm bolts VW# n 908 235 01
    (2 per side, 4 total) front motor mount bracket shorter 18mm bolts VW# n 906 630 02

    Control arm removal and installation procedure
    To check control arms,
    inspect the rubber bushings - they should not be torn. Some minor cracks in the rubber when the control arms are extended are considered normal. These cracks should go away when in the arms are in the normal resting position. To inspect ball joints in general, with the front of the car raised so that there isn't weight on the front suspension/tires, hold the tire at the 3 and 9 o'clock position and shake the wheel/tire back and forth. It should be tight. Grab each individual control arm and shake it near the ball joint. It should not be loose.

    To remove and replace control arms,





    first note the angles of all the control arms when the car is in the normal, level resting position. During installation, only tighten the control arms to their final torque when the suspension is in its normal, level resting position. If the control arms are extended (wheel is hanging down) and tightened in that position, the bushings will be preloaded and will quickly wear out! This is the general rule when installing suspension bushings on any car, not just your VW/Audi. *A few cars require the rear suspension to be loaded by up to an inch.

    If you plan on removing the steering knuckle from the car,
    first loosen the axle bolt. If it's OEM hardware, it's either a 27mm bolt or a 17mm allen head. The difference in the bolt style was the threads used on the axle (M14 vs. M16). The OEM hardware on your VW Passat TDI axle should be a 17mm allen.

    Loosen all the front wheel lug bolts a single turn. You must loosen the lug bolts before raising the car.

    Engage the parking brake, jack up the car, rest car securely on jack stands at the factory jack points, and make sure the car is safe and secure before doing anything else.

    Then finish removing the front wheels.

    Note the various parts. Spray some PB Blaster, liquid wrench, or any penetrating lubricant on the various bolts/nuts and let soak. Gently tap them with a hammer to let the penetrant soak in further. As referenced in 1000q: some basic auto mechanics tips, lubricant can reduce the effort needed to loosen rusty hardware by 40-80%.
    [​IMG]

    Optional - tie rod end removal
    (shown above and highlighted in yellow below) The outer tie rod ends should be replaced during a full suspension overhaul. This is only a summary, see 1000q: tie rod end replacement for the full DIY and video.

    Remove the vertical 1x 13mm bolt holding the tie rod end and the 16mm horizontal nut/bolt pinching it in place. If they are rusted/seized, let the penetrating lubricant sit for a while and gently tap them with a hammer. You must remove the 16mm horizontal nut all the way because it locks the tie rod in place. The head of the 16mm pinch bolt has a flat spot to lock it in one position. Use the bolts to tap the tie rod end out AFTER the pinch bolt has been removed.
    [​IMG]

    Upper arm removal
    The 16mm upper pinch bolt can get rusted and rounded off so be careful when trying to get it out! The pinch bolt is the horizontal bolt/nut that was removed in the pic above and shown in the first pic. I strongly recommend soaking the pinch bolt/nut and ball joints in PB Blaster or another penetrating lubricant before starting the project. If it's rusty, give them a squirt the day before and as soon as you get the wheel off. After the pinch bolt's nut is removed, use a punch to tap the pinch bolt out from the rear - they sometimes snap in half so I do not suggest forcefully prying the head out.

    After the upper pinch bolt is removed completely, remove the upper 2 ball joints. The pic above shows removal of one of them. The ball joints are very tight and will probably be seized in place. Tap the ball joints with a hammer to let the PB Blaster penetrate a little more and reapply as needed. Use a punch or 3/8 drive extension and hit them hard repeatedly from the bottom to push them up and out. Do not use a pry to open the joint since this can crack the steering knuckle. I've found that you can stick a screwdriver in the gap and shake it with light force to loosen it up but do not pry it open since many have cracked steering knuckles doing this! It's hard but just keep hitting them and it'll slowly come out.

    When the ball joint is disconnected the control arm rests in a raised position. This is an example of the approximate normal resting position. If you were to tighten the control arms with them hanging down, the bushings would get worn out quickly since they want to be in the hanging down position.

    Remove the upper control arms by loosening the bolt/nut on the mounting plate (shown below) . If you are also removing the strut/spring, I recommend leaving the upper control arms attached to the mounting plate and removing it from the car as an assembly (3x 16mm) bolts above the wheel well in the engine compartment.

    To remove the mounting plate and struts
    There is a flat lock washer holding the mounting plate in place. It was used on the assembly line and will not be reused. Pry or cut it off.
    [​IMG]

    Open the hood and look at the top of the shock towers. The below picture is on the driver's side. Remove the 3x 16mm mounting plate bolts holding the mounting plate to the body. If you're not removing the strut an alternative method is to dig out the painted caps (one is circled in light blue below) to get access to the upper shock bolts. Then you can remove the upper shock bolts. I suggest just removing everything as an assembly because the painted caps are painted in place and will probably get mangled during removal.
    [​IMG]

    Counterhold the 18mm shock lower bolt/nut (yellow box in the below picture) to loosen it and remove the bolt. The shock is now free on the top and bottom. You may have to push the control arms down a bit for clearance to remove them.

    *NOTE - as you remove the control arms and shock, the steering knuckle and brake will try hang down. Don't let it hang down because it will stress the CV joint, the brake line, and the ABS sensor wire. Support the brake rotor from below and the side so that it can't fall down. If the brake line is internally stressed it could break, resulting in loss of braking action. In case you noticed it, the wood block and jack seen below wasn't supporting the weight of the car, it was a backup only! Never use a hydraulic jack as the primary method of supporting the car!
    [​IMG]

    Optional step/pictures - steering knuckle removal
    As mentioned above, the alternative to supporting the knuckle is to remove the entire knuckle from the car. I would avoid this unless needed because it's a pain to get air out of the brake lines. Air in the brake lines can cause loss of braking! To remove the knuckle, remove the axle bolt - the bolt is a single use stretch bolt so don't reuse it! As mentioned in the introduction, you must loosen the bolt when the car is on the ground. Once it's loosened, you can remove it during this step. See 1000q: CV boot replacement for more details. Then remove the brake line (11mm union). To remove the ABS sensor wire (highlighted below), pry the rubber plug out of the wheel well. The 2 plugs are inside the wheel well as pictured below. If you can't get the ABS wire out of its metal bracket, you can remove the 10mm bolt holding the bracket (highlighted below). See 1000q: brake fluid bleed to get the air out of the lines. You must use a VCDS cable to actuate the ABS pump and get trapped air out of the lines.
    [​IMG][​IMG]

    Lower control arm removal
    Counterhold the 16mm bolt/nut to remove the sway bar and sway bar endlink from the front lower control arm. If you're doing a complete suspension overhaul, most kits include replacement sway bar endlinks. You should also replace the sway bar bushings, see 1000q: sway bar bushing replacement for more details.

    Remove the lower control arms at the ball joints first (one is highlighted in yellow below). Then remove the control arms at the subframe (1x 18mm bolt/nut per arm). The problem is that the rear control arm bolts will hit the body and can't be removed! This problem area is shown below as "no clearance". During car assembly, they put the control arms on the front subframe and raise it into the car - the assembly workers never have to deal with that annoying bolt!
    [​IMG]

    To remove the bolt you must lower the rear subframe about 1" to get more clearance. Note: the 18mm subframe bolts are single use only stretch bolts and are designed to be torqued to their final value only once. After getting the subframe and new control arms back in place, remove the used bolts and put in the new bolts, one at a time. While some people reuse them, I would not reuse them more than once. My car got all new bolts.

    Caution: Before removing the 18mm subframe bolts, first loosen them by 1/2" just to get them loose. Do not remove them all the way or else the subframe will fall down and cause serious injury and/or damage! Before loosening the subframe bolts, make sure the subframe and engine/transmission are securely supported from above or below! First remove the 2x 13 rear subframe brace bolts. Then loosen the 1x 18mm rear subframe bolt by about 1/2" at first.
    [​IMG]

    Below is about how far the subframe needs to come down for clearance. The annoying bolt is shown halfway out. Caution: only lower the subframe far enough to remove the 18mm bolt! Do not lower it any further! Make sure the rest of the subframe bolts are secure so that there is no risk of the subframe falling down! If the subframe falls down it could result in serious damage, injury, or death!
    [​IMG]

    The control arms are now removed. Installation is the reverse of removal, see notes below.

    Again, always tighten the suspension bolts in their normal resting position only! If the suspension bushings are tightened in a preloaded position, they will wear out due to overstress. After the control arms are in place and the rear subframe bolt is in place, tighten the subframe bolts to get the suspension in position. Leave all the other bolts/nuts a little loose before tightening any of them. Lower the car to the normal resting position and give it a few shakes. Then tighten all the bolts to their final torque.

    Some of the nuts are single use only nuts. They are weakened during reuse and if they are reused, some blue medium strength threadlocker will help prevent loosening up or backing out. I would not reuse the 18mm control arm bolts since they are carrying the control arms and they tend to get rusty/threads damaged during removal.

    If you removed the driveaxle, see 1000q: CV boot replacement for axle bolt torque specs and more details.

    Torque specs
    Subframe/shock
    (1x per subframe corner, single use only) 18mm long subframe bolt (for both front and rear): 81 ft-lb + 1/4 turn
    (2x per side) 13mm rear subframe bracket bolts: 15 ft-lb
    (3x per side) mounting plate 16mm bolts: 55 ft-lb
    (1x per side) lower shock 18mm bolt/nut: 66 ft-lb
    (2x per side, single use or threadlocker) upper shock - mounting plate nuts: 16 ft-lb
    (1x per lower control arm, single use only) 18mm bolt/nut connecting subframe to lower control arm: 59 ft-lb + 1/4 turn
    (1x per upper control arm, single use only) 18mm bolt/nut connecting mount plate to upper control arm: 37 ft-lb + 1/4 turn

    lower ball joint nuts: 74 ft-lb (single use only)
    upper ball joint horizontal pinch bolt/nut: 30 ft-lb (single use only)

    outer tie rod vertical bolt: 5 ft-lb (it's a single use bolt so use threadlocker if you reuse it)
    outer tie rod horizontal pinch bolt/nut: 33 ft-lb (it's a single use nut so use threadlocker if you reuse it