How can I replace torsion spring of my garage door?

SOURCE: fix broken torsion bar spring in 1999 mercury

Do you mean the sway bar in the front? or back?

If so, then this is the solution:

Front Sway Bar Removal & Installation To Remove:
WARNING
If equipped with a fire suppression system, de-power the system.
WARNING
The electrical power to the air suspension system must be turned off prior to hoisting, jacking or towing an air suspension vehicle. Failure to do so can result in unexpected inflation or deflation of the air springs, which can result in shifting of the vehicle during these operations. Turn the air suspension service switch off.

1. Remove the wheel assemblies.
2. Remove the nuts and the stabilizer bar link.
3. Remove the stabilizer bar bracket nuts.
4. Remove the front stabilizer brackets and the front stabilizer bar.

NOTE: Use the hex holding feature to prevent the studs from turning while removing the nuts.
To Install:
NOTE: Use the hex holding feature to prevent the studs from turning while installing the nuts.

1. Install four new nuts, brackets and sway bar. Tighten the bracket nuts to 63 Nm (46 ft. lbs.).
2. Install two new nuts and stabilizer links. Tighten the nuts to 63 Nm (46 ft. lbs.).
3. Lower the vehicle.
4. Enable air ride suspension and the fire suppression system if equipped.

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Rear
Sway Bar Removal & Installation To Remove:
WARNING
If equipped with a fire suppression system, de-power the system.
CAUTION
Suspension fasteners are critical parts because they affect performance of vital components and systems and their failure can result in major service expense. New fasteners must be installed with the same part number or an equivalent part if installation is necessary. Do not use a replacement part of lesser quality or substitute design. Torque values must be used as specified during reassembly to make sure of correct retention of these parts. Orientation of the fasteners is also important on all rear suspension arms. Make sure the fasteners are installed in the same direction as they were in when removed.
WARNING
The electrical power to the air suspension system must be turned off prior to hoisting, jacking or towing an air suspension vehicle. Failure to do so can result in unexpected inflation or deflation of the air springs, which can result in shifting of the vehicle during these operations. Turn the air suspension service switch off

1. Raise and support the vehicle.
2. Remove the two nuts, washers and bushings.
3. Discard the nuts.
4. Remove the two nuts, the washers and bushings, and the stabilizer bar links.
5. Discard the nuts.
6. Remove two bolts, brackets and the stabilizer bar.

To Install:

1. Install stabilizer bar brackets and bolts. Tighten to 18 ft. lbs. (25 Nm).
2. Install washers, bushings, links and nuts. Tighten to 15 ft. lbs. (20 Nm).
3. Lower the vehicle.

SOURCE: How Do I fix new garage door?

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