924/944/968 Frequently Asked Questions

944 Control Arm Replacement Procedure

The following note was created by Michael Kehr. It applies to 85/2-forward 944-series cars.

General Information

The purpose of this procedure is to supply basic but complete information for the removal and installation of aluminum 944 control arms installed on 1985/2 and newer 944-series cars. The procedure is intended for the amateur/novice home mechanic with a basic set of metric tools.

For the 1985/2 model year, the 944-series front control arms were changed from a steel design to a light alloy aluminum design. The rubber bushing/bearing mount was redesigned and the caster eccentric modified.

Prior to the 1985/2 model year, steel control arms were used in the 944. This note does not cover replacement of steel arms.

All 944-series control arms have a larg ball joint that connects the outboard end of the arm to the steering knuckle. Over time, this ball joint can develop free-play that indicates wear and possibly damage inside the joint. The shaft or "stud" at the top of the ball can also fatigue and fracture, particularly in high mileage cars, and cars that see a lot of stress at the race track.

On the earlier steel arm, the ball joint is available separately as a service/repair part, and can be replaced in the arm, as is the case with 911's. With the later aluminum control arm, the ball joint is not available as a separate part. The "cup" of the ball joint is the control arm itself. The complete arm must be replaced, or it can be sent out and rebuilt (not authorized by Porsche). One of the rebuilders offers a three year warranty. Call and ask about their rebuilding techniques, not all do it the same and quality varies. These rebuilt arms are not recommended for serious racing. I would buy a new unit, or get the steel Fabcar arms with the replaceable ball joint and high quality bushings.

In the past few years, Porsche Cars North America (PCNA) has lowered the price of their control arms to compete in the rebuilding market. The difference in cost between a rebuilt unit and a new one is not all that great, so shop around to get the best price. Keep in mind that the new part carries a warranty backed up by Porsche.

When purchasing the arm, make sure that you have the right part number for the model and year of your car. Part numbers change over time as supersessions and improved versions of parts become available. There is a list below, but double-check with your favorite Porsche dealership's parts department to confirm the correct current part number for your Porsche.

How do you know if you need to replace your ball joints/control arms?

There is a rubber boot that encloses the joint; inspect the boot for cracks or other damage. Another sign is clunking in the left or right front suspension; it starts off very subtle but will get worse as time goes on. I damaged my left ball joint when I hit a pot hole, it hit real hard!

You can also check for free-play in the ball joint. Use a large pair of pipe wrench pliers (commonly called "channel lock pliers"). Put the upper jaw on the steering knuckle tab into which the ball stud is inserted. Put the lower jaw of the pliers on the underside of the control arm. Compress the pliers. If you see more than roughly a millimeter of play, the ball joint requires replacement. (Many manufacturers publish specifications for allowed play in ball joints. Unfortunately Porsche does not.)

You cannot measure fatigue or damage to the ball joint stud. It would be possible to check it using a dye penetrant test, but this is beyond most shade tree mechanics' abilities. The only realistic approach to this problem is probably automatic replacement as some service interval, perhaps 100,000 miles for street-only cars, 50,000 miles for track cars.

Do I need to replace both arms at the same time if only one is bad?

It is not strictly necessary. If you have the funds it would probably be a good idea, since the other arm is likely to be of the same age and not far behind the first in needing replacement. Moreover, replacing either arm required realignment, and so doing both at once can help you avoid a second trip to get the car aligned.

Preparation

Prior to removing parts, apply penatrant to all fasteners, let chemical soak, repeat. Rost Off by Wurth or PB works great. Make sure that you have all required parts that are needed for the job before you start.

Time Allotment

About 2.5 hours, without any major problems.

Tool and Supplies

Parts

As covered above, there have been a number of versions of the aluminum control arm. Check with your Porsche dealership parts department for the latest and correct part numbers for your particular model. At the time of writing, the FAQ maintainer's best understanding of the correct part numbers is as follows:

944, 944 Turbo, model years 85/2 through 86

944-series cars, model years 87-forward

944-series cars, model years 87-forward, with M030 or M758 options

This covers both cars with the "sports chassis" competition package (M030), the model year '88 944 Turbo S (M758), and all 944 Turbo cars from model year '89-forward.

These parts differ from the above only in the stiffness of the front bushing pressed into the arm. For this reason, they may be used to upgrade the suspension on cars not delivered from the factory with options M030 or M758.

Updated M030, M758 Arms

The following parts are reportedly available as supersessions to the M030, M758 parts listed above.

Common hard parts

The two VM12 x 1.5 lock nuts (N.022.141.4) on the caster eccentric (rubber mount at rear of the control arm) supersede the original use of two M12 x 1.5 lock nuts (N.021.131.1) in this application. The torque value for them has been increased accordingly, noted below.

Suppliers

Rebuilt Control Arms

Source Price Telephone
Zims $239.00 +1.800.356.2964
Dynamic European Technologies Inc. $149.00 +1.713.661.2780
Tweeks $199.00 +1.800.421.3776

All of the prices are US$, and are with exhange of your old control arm.

New Control Arms

Type Source Price Telephone
Fabcar racing control arm OG Racing   +1.800.934.9112
original equipment PCNA dealer $355.00 +1.800.PORSCHE

Look for dealer discounts of 10% - 25%.

Removal

  1. Raise side of car that you will be working on with a floor jack; if you are changing both arms, raise front of car. In either case, secure with properly rated, good quality jack stands. Also utilize the correct jack points (refer to owners manual). Emergency brake on, rear wheels blocked and negative terminal disconnected from battery. (Better safe than dead!)
  2. Remove wheel(s).
  3. Remove bottom engine cover trays. On cars with a single plastic tray, you will have to remove six to eight M6 bolts with a 10 mm socket and ratchet. On the 944 Turbo and S2, there are auxiliary trays held on with philips head fasteners.
  4. Mark with scribe or paint pen the caster eccentric bolt alignment to arm (rear of control arm), and rear control arm bushing assembly alignment to chassis. It may be necessary to replace this bushing assembly; check for wear and rubber deterioration. It is important that this eccentric bolt is marked prior to removal for proper caster alignment. This does not guarantee that the alignment will not change, there will be different tolerances upon assembly (new parts bushings etc.).
  5. The following is a list of fasteners that will be removed during this procedure:
    1. Sway bar clamp nuts/bolts (2)
    2. Sway bar bushing assembly nut/bolt/rubber bushings(2)/washers(2)(center of A-arm).
    3. Pinch bolt and nut on bottom of spindle (secures ball joint shaft to spindle).
    4. Front control arm nut/bolt (attaches front of control arm to bottom of cross member).
    5. Rear control arm bushing mount assembly/bolts(2)/washers(2) (attached to chassis)
    6. Eccentric rear control arm bolt/nut/washer (connects control arm to rear control arm bushing mount.
  6. Remove bolt/nut from bottom of spindle/strut.
  7. Remove bolts(2)/nuts(2) from sway bar clamp bracket.
  8. Remove nut/washer/bushing from top of sway bar bushing assembly, tap bolt out from top of a arm, remove lower washer/bushing and bolt. Check these bushings for wear and rubber deterioration, and if in doubt, replace them. If you do this, I would replace all the bushings at the same time.
  9. Remove front control arm bolt/washer/nut from cross member. This bolt is rather long, the steering tie rod/spindle assembly must be moved in order to slide the bolt out. Don’t worry there is plenty of play here. Tap on bolt to get it started, it may have to be tapped through while moving the arm side to side.
  10. Remove rear control arm bushing mount bolts(2)/washers(2)
  11. Discard the the lock nuts that you have removed.

    If you are not replacing the rear bushing mount assembly it is only necessary to remove the front most nut/washer of the rear part of the control arm. You can then transfer this assembly to the new control arm without moving the eccentric bolt position, relative to the bushing/bearing mount.

    If you are removing the rear bushing mount from the eccentric bolt, make sure the eccentric bolt center is marked in relation to the rear of the arm! You will transfer this mark to the new arm. Remove both nuts from eccentric and mount, remove from arm.

  12. With a rubber/plastic mallet tap the outer end of the control arm so that the ball joint spud comes out of the bottom of the spindle/strut assembly.
  13. Control arm should now be free. Remove it from the car.

I know I am making a big deal concerning the eccentric and it seems confusing, but it will all come together when you actually see how it works.

Installation

All lock nuts must be replaced. The lock nuts are not reusable! Use anti-seize on the bolts, thus preventing future problems with stuck nuts.

  1. Transfer scribe mark from old a-arm to replacement arm. This part is not necessary if you did not replace the rear bushing mount.
  2. Attach eccentric bolt/bushing mount to rear of new/rebuilt control arm, depending on what you removed. Align scribe marks of eccentric to arm, replace with new nuts and torque to spec, making sure that marks stay aligned!
  3. Place arm in position, fitting front arm bushing in cross member.
  4. Align bolt holes and replace bolt/washers/nut.
  5. Attach rear bushing mount with bolts/washers to chassis; align to scribe marks, torque to spec.
  6. Position ball joint spud so it fits into bottom of spindle assembly, making sure that spud is pushed up all the way. Replace bolt and nut.
  7. Attach sway bar bushing mount into control arm, replace with new lock nut.
  8. Attach sway bar bushing clip to chassis bracket. The shock may have to be depressed in order to align the bolt holes. I used the jack to depress the control arm/strut. Replace bolts and new lock nuts.
  9. Once sway bar mounts are positioned correctly, torque all lock nuts to specs.
  10. Replace wheel. Tighten nuts in a star pattern in order to attach wheel properly.
  11. Torque all nuts to spec. (see below)
  12. Check all work for mistakes, and those extra fasteners; where did they go?
  13. Lower car, remove rear tire blocks, and enjoy those new control arms.
  14. Test drive car. How does it feel? If you followed this procedure carefully, you will probably not experience any alignment problems. When you replace your tires you can have an alignment shop check the front out and make sure it is in spec. Make sure that you use a reputable shop that is familiar with Porsches, especially 944’s. Just because a shop has a lot of money invested in equipment does not automatically make them qualified to do work on Porsches. This is one of the reasons that I do as much work as possible on my Porsche; very few mechanics will take the time and care that is required to maintain your car properly, like you would.
  15. Pat yourself on the back; you did that yourself!

Torque Specifications

Location   Thread   Tightening Torque
Control arm to cross member, lock nut   M12 x 1.5 mm   48 ftlb, 65 Nm
Control arm bearing assembly (caster eccentric) to body, bolt   M10   34 ftlb, 46 Nm
Control arm bearing to control arm, lock nut   VM12 x 1.5   74 ftlb, 100 Nm
Clamp for stabilizer (sway bar), lock nut   M8   17 ftlb, 23 Nm
Stabilizer linkage to control arm, lock nut   M10   18 ftlb, 24 Nm
Control arm ball joint to steering knuckle, lock nut   M10   37 ftlb, 50 Nm
Light alloy wheel to hub, lug nut   M14   96 ftlb, 130 Nm

Note that the torque spec for the control arm bearing assembly to the control arm is for the updated VM12 x 1.5 lock nuts. The older style M12 x 1.5 lock nuts were torqued to 63 ftlb, 85 Nm.

Sources

If you have any questions/corrections/suggestions please feel free to contact me, Mike Kehr
e-mail: mikehr@earthlink.net
home phone: +1.609.645.8167

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