Some tools that you're going to need is a 3/8 wrench, half-inch wrench, a 7/16 wrench, a 9/16 wrench and possibly a 9/16 socket or an adjustable wrench.
Usually the set screws on the springs are either 3/8 or 7/16 that's the most common sizes with 3/8 being the most common size.
Unload the tension from the spring that's not broken. do this in a safe manner by wearing protective goggles.
The most important tool that you need are winding bars. these are the bars that will be inserted into the holes in the spring.
To unwind this spring safely and to rewind the new spring safely the first thing to do is to make sure that the bar is the proper size.
Slide the bar into the hole to make sure it fits. You will know if it goes all the way in the hole and is secure.
To unwind this spring you’re going to securely put the bar into the spring. the tension is going to want to pull down towards the door so you want to put support against the rod.
Loosen the set screws and back the set screws far enough out that they're not going to drag around the torsion bar.
Unwind it one quarter turn at a time.
Hold lift up, pull the rod out, bring it down, rest it against the door. Repeat until the spring is unwound.
Now that you've got the spring fully unwound, a common thing that happens these torsion bars screws get tightened down so to release the bars you will hold the bar in the spring and use a hammer on the side to knock the spring.
If you see indentations left in the torsion bar it is an indication that there's a little bit of tension left on the spring. To take the rest of the tension off you're going to make about 2 turns (like the previous steps).
Now that this bar is completely free, the next thing to do is to unbolt the springs from the center bearing support.
Use a 9/16 wrench and we're to loosen the bolts and then remove them. don't throw these away you'll need them.
Now onto the spring, loosen the set screws and slide it off towards the end of the river.
Make sure that it is able to slide smoothly. If not, use a little bit of silicone spray.
optional tool that you want to add handy
Now that you've got the springs disconnected from the center bearing plate and is slid out towards the ends the next step is to take the cable drums loose which is what the cables roll up.
You don't want these cables to fall down next to the door so to take this cable and wrap it right through the top bracket so it will hold it in place.
loosen the set screws and the cable drums.
When you loosen them, the cable drum should slide freely. but just to ensure it does slide freely, rub it with a file.
There's two ways to attack this portion: if the shaft slides back and forth from side to side easily, you're going to slide it from one side the other to allow you to access to the spring on the other side.
When you look over at the other side now, you'll see where the shaft is come out of the bear and you now have access to that spring.
Once you were able to slide the shaft over to the other side, the shaft is now free from the bearing plate which will allow you access to swap the broken spring out with a new spring.
The first thing you're going to do is repeat what you did on the other side by tying the cable up so it doesn't fall down.
Take the set screws loose on this particular cable drum.
Optional: file where the set screws are to remove any burrs and spray it with some silicone to help the spring slide off easily and help it slide back into the bearings.
Now that we've got that sprayed, slide the spring out.