Torsion Bars – Removing, Replacing, and Indexing

Overview

This guide walks you through removing, replacing, and reindexing the torsion bars on your Porsche 944 with a 16v engine. Torsion bars control the rear suspension’s ride height and stiffness. You might need to remove them to adjust the ride height or upgrade to stiffer bars for better handling. While the removal and replacement are straightforward for someone with mechanical experience, reindexing can take time and patience to get the ride height just right.

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Tools Required

• Jack stands and floor jack
• Metric socket and combination wrench set (e.g., 13mm wrench, 17mm (11/16 inch) wrench)
• Pry bar
• Measuring device (fabricated as described in the procedure)
• Heavy-duty strap
• Bungie cords or wire (for hanging axles)

Parts Required

None (assuming replacement torsion bars are provided by the user)

Required Additional Procedures

Steps in these procedures are required to complete this process:

• Rear Sway Bar Removal and Installation

Step-by-Step Procedure

Step 1: Measure the Current Ride Height

1. Park the car on level ground and measure the ride height from the ground to the top-center of the rear fender well (above the wheel). A good target is about 25 inches (63.5 cm).
2. Decide how much adjustment is needed. The eccentric bolt on the spring plate allows up to 1 inch (2.5 cm) total adjustment—about 0.5 inches (1.3 cm) up or down if centered.

Step 2: Prepare the Vehicle

3. Raise the rear of the vehicle using a floor jack and secure it on jack stands.
4. Follow this link to ensure this step – Rear Sway Bar Removal and Installation – of the process is followed accurately to remove the rear sway bar and drop links.
5. Lower the vehicle back to the ground and bounce the rear end a few times to settle the suspension.

Step 3: Measure the Loaded Spring Plate Height

6. Fabricate a measuring device with two holes matching the bottom two bolts on the torsion tube end cap (see the Rear Suspension diagram for reference).

7. With the car on the ground, measure the height of the spring plate relative to the torsion tube end cap. Mark this “loaded” position on your device. This can be tricky with the wheel in place.

Step 4: Remove the Torsion Bar

8. Raise the rear of the vehicle again and secure it on jack stands.
9. Remove the rear wheels.
10. Unload the torsion bar by removing the bottom rear bolt on the torsion tube end cap (see Rear Suspension diagram, Item 5).
11. If replacing the torsion bar, use your measuring device to mark the “unloaded” spring plate position.

12. Disconnect the rear brake lines at the calipers and unplug the brake pad wear sensors.
13. Unbolt the rear axles from the trailing arms and hang them out of the way with bungie cords or wire.
14. Remove the bolt attaching each trailing arm to the torsion tube (see Rear Suspension diagram, Item 1).
15. Support the trailing arms from the transmission crossmember with a heavy-duty strap to prevent damage or injury when they hang free.
16. Remove the three nuts and bolts holding each trailing arm to the spring plate (see Rear Suspension diagram, Item 2). Tap the eccentric bolts if they stick.
17. Remove the nut and bolt securing the torsion tube cantilever arm to the chassis mount near the wheel well (see Rear Suspension diagram, Item 3).
18. Place a floor jack under the center of the torsion tube assembly and raise it until it just touches the tube.
19. Remove the nut and bolt attaching each torsion tube end cap to the chassis (see Rear Suspension diagram, Item 4).

20. Gently pry the torsion tube assembly free from the chassis, alternating sides, and lower it with the jack until you can access the torsion bar.
21. Remove the remaining three bolts from each torsion tube end cap.
22. Remove the end cap and spring plate, then pull the torsion bar out of the tube.

Step 5: Install the New Torsion Bar

23. Measure the loaded-to-unloaded range of the old torsion bar using the marks on your device.

24. Calculate the new torsion bar’s loaded-to-unloaded range using this formula: (Old Range × Old Diameter⁴) ÷ New Diameter⁴. For example, swapping from 25.5mm to 30mm bars with a 50mm range gives: (50 × 25.5⁴) ÷ 30⁴ = 36mm.
25. Mark the new unloaded position on your device by measuring the calculated range down from the loaded mark.
26. Slide the new torsion bar into the torsion tube.
27. Install the spring plate and end cap, aligning the spring plate to the new unloaded mark. Secure with at least two bolts.
28. Raise the torsion tube assembly into place with the floor jack.
29. Bolt the trailing arms to the spring plates, centering the eccentric bolts.
30. Reattach the trailing arms to the torsion tube.
31. Secure the torsion tube cantilever arm to the chassis mount near the wheel well.
32. Attach the end caps to the chassis.

Step 6: Check and Adjust Ride Height

33. Remove the jack stands, lower the vehicle, and bounce the rear end a few times.
34. Measure the ride height again. If it’s within ±0.5 inches (1.3 cm) of your target, adjust the eccentric bolts on the spring plates.
35. If the adjustment needed is more than 0.5 inches (1.3 cm), lower the torsion tube assembly, reindex the torsion bars (see Step 7), and repeat until correct.
36. Once the ride height is correct, install any remaining end cap bolts and follow this link to ensure this step – Rear Sway Bar Removal and Installation – of the process is followed accurately to reinstall the sway bar.

Step 7: Reindex the Torsion Bars (If Needed)

37. Understand that the torsion bar has 40 inner splines (9° per spline) and 44 outer splines (8.18° per spline). Moving one spline changes ride height by about 2.58 inches (6.6 cm) inner or 2.35 inches (6 cm) outer.
38. To lower the car, rotate the inner end counterclockwise or the outer end clockwise. To raise it, do the opposite.
39. Lower the torsion tube assembly, adjust the spline position, and reinstall. Recheck the ride height and repeat as needed.

Post Procedure Checklist

• Check that the ride height matches your target (e.g., 25 inches (63.5 cm)).
• Ensure all bolts are tightened securely (e.g., end cap bolts, trailing arm bolts).
• Verify the brake lines and wear sensors are reconnected with no leaks.
• Confirm the rear axles are bolted back to the trailing arms.
• Test drive 5 miles (8 km) and recheck ride height after a few days to ensure it settles correctly.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube