944 Control Arms - General Information, Rebuilding, and Aftermarket Replacements

Introduction

The alloy control arms used on late cars have a known weakness. The ball joint rides inside a nylon cup pressed into the aluminum housing. Under normal cornering loads, the geometry of the control arm, spindle, and ball joint housing creates a side-loading force that pushes the ball joint pin against the nylon cup. This causes premature cup wear. Once the cup is worn enough to allow metal-to-metal contact, the housing itself wears, and the ball joint pin may eventually crack and shear. This failure mode is accelerated by hard cornering (autocross, track use) and is worse on cars with lowered front suspensions where the control arm geometry has changed.

Replacement ball joints for the alloy arms were not originally available separately. Early on, the only option was a complete new control arm. Rebuild services and DIY kits are now available. The kits come in two materials:

• A nylon-bushing kit replaces the bushings only, using nylon similar to the original equipment. It does not include new ball joints — the ball joints are rarely damaged even when the bushings are extremely worn, so reusing them is normal.
• A bronze-bushing kit comes with bronze bushings and chrome-moly ball joints. This is the better choice for cars that are frequently driven hard.

For ball joint boot replacement only: install the boot from an early cars ball joint. The Porsche part number for the early ball joint is 171 407 365 G.

While this article covers the alloy control arms primarily, upgrade options for the earlier steel-arm cars are also discussed.

Control Arm Ball Joint Boot Replacement

The grease boot on alloy control arm ball joints is sometimes torn during control arm removal or installation. Replacement boots are not sold separately, but the boot from an early cars ball joint (part no. 171 407 365 G) can be used as a substitute.

Rebuild Procedure

Based on a procedure originally written by 951 RacerX.

1. Remove the control arms from the vehicle (see SUSP-07).
2. Remove any epoxy from the bottom of the control arm ball joint to expose the circlip retaining the ball joint.
3. Remove the rubber grease boot from the control arm; retain the boot retaining spring.
4. Place a large socket over the pin side of the ball joint and a nut or small socket against the bottom cover of the ball joint.
5. Squeeze the assembly in a vise enough to allow the circlip to be accessed and removed.
6. Use a small screwdriver to pry the circlip out of its groove in the control arm.
7. Disassemble the ball joint assembly from the vise.
8. If using a kit that replaces only the bushings (ball joint pin reused), inspect the pin carefully for cracks or unusual wear. A cracked pin must be replaced.
9. Place the top ball joint bushing into the opening in the control arm, aligned evenly.
10. Press the bushing into the control arm using a vise and a socket slightly smaller than the bottom opening of the control arm (slightly over 30 mm diameter). Place a piece of wood between the back of the control arm and the vise jaw.
11. Apply CV joint grease to the cup and to the ball.
12. Insert the ball into the cup, followed by the lower cup, spacer ring, spring, another spacer, and cover plate.
13. Squeeze the assembly in the vise and install the circlip.
14. Apply epoxy to the bottom of the ball joint opening to retain the circlip.
15. Reinstall the control arm (see SUSP-07).

Aftermarket Control Arms

Aftermarket control arms with replaceable ball joints are available for both early and late cars. These are generally intended for performance or track use. Availability varies by supplier; confirm fitment and pricing when ordering.

Options have historically included:

• Tubular steel arms with replaceable ball joints and spherical cross-member bushings
• Billet aluminum arms with a replaceable ball joint and spherical cross-member bushing. These are direct bolt-in for 1985.5–86 and 1987–95 944s and 968s, and can also be adapted to 1983–85 cars.
• Reinforced steel arms available for both early and late offset 944s, compatible with both early and late sway bar mounting

Specify your model year and sway bar type (early or late mounting, OEM or aftermarket) when ordering.