To reinforce the torque boxes you have 1 of 2 options. You can either weld the seams or you can get a reinforcement kit like I did. After installing the kit I would almost recommend welding them until you need more support. The kit isnt bad to install, its just real time consuming and you need an extra set of hands to help.
Before you start you need to remove the back seat and scrape all the sound deadening off the floor from under the seat and up into the trunk area. I removed the rear axle assembly since the axle tubes have to be welded up. Since the control arms will be removed anyway, there isnt much left to unhook to get the rear axle out. There is a lot of room to work with the axle assembly out so I would go that route if doing this kit. Before I started, I painted all the parts that were to be on the outside of the car
Lower torque box kit:
From inside the car, unplug the abs sensor plug that should be located on both sides by the quarter panel trim. With the sensor unplugged, push the rubber grommet that the sensor wire goes through, down through the floor. From under the car, unbolt the bracket that holds the sensor wires with an 8mm socket. Once unbolted, pull the wiring through the hole and set it aside. Next, ubbolt the bracket that is holding the ebrake cable which will be located right next too the bracket for the abs wiring
On SN95 Mustangs (96-04) you need to open up the hole that the torque box bracket goes into.
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Once the opening has been made big enough, slide the bracket up into the hole and hold in place with a control arm bolt. (On the kit I got, I had to open the hole in the bracket big enough for the control arm bolt to fit.) There are left and right sides to the lower box kit. With the bracket held in place with the control arm bolt, the other 4 holes should be up against the floor. Using a 3/8" drill bit, drill from under the car through the 4 holes. From the inside, line up the 6x6 plate with the holes. (There are left and right of these also) Once the holes are aligned, bolt together using the supplied hardware that comes in the kit. The kit I got says to put the bolts up from under the car but I did it the other way with the bolts going down through the floor. That way if a nut happens to come off, your not driving over the 1 1/4" long bolt.
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After the plate and bracket were bolted into place, I drilled a 3/4" hole down in the center of the bolt pattern. A 3/4" hole is big enought to slide the plug for the abs wiring through. Cut the rubber grommet off the wiring assembly and slide the wire up thought the hole. Plug the wire back in. Use silcone around the wiring to fill the hole.
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The lower kit is now done.
Upper torque box kit
Drill a 1/2" hole straight up (at a right angle the sheet metal on the inside of the torque box) through the 1/2" hole that is already in torque box. The inner hole on my car was more of an oval so if yours is also, dont start with that one.
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After the hole is drilled, put the torque box bracket in place and slide a 1/2" bolt throught the floor and have someone hold it there. From the inside of the car, slide the cruved floor plate over the bolt. Put the angled spacer over the bolt and snug it down with the supplied nut. With the plate snugged down, drill the other 1/2" hole the same way you did the first one. I used a unibit to inlarge the holes in the floor slightly to better align the curve floor plate. Put another bolt in the second hole and snug that one down the same way you did the first.
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Have someone hole the bottom of the curved floor plate with a pc of wood so it is tight against the floor. I cut a piece of wood so it would hold the plate tight. From under the car, drill the 2, 3/8" holes that are in the front of the bracket. Bolt in place with the supplied 3/8" bolts.
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Tighten all the bolts up but dont tighten the 1/2" bolts to much or it will start to suck the floor down.
If you are going to weld the floor plates in place, trace around the outside of the plates and remove them. Now take and remove the paint along the lines that you just made by tracing the plates. Bolt everything back in place and weld the plates to the floor. After everything is welded, paint the exposed welds and plates to prevent rusting.
Reinstall the rear seats and the rear axle assembly and you are finished.
If you have any questions or if you know I forgot anything, please let me know
Edit: thanks to caspergt for informing me before hand to get a long 1/2" drill bit for drilling the holes
Before you start you need to remove the back seat and scrape all the sound deadening off the floor from under the seat and up into the trunk area. I removed the rear axle assembly since the axle tubes have to be welded up. Since the control arms will be removed anyway, there isnt much left to unhook to get the rear axle out. There is a lot of room to work with the axle assembly out so I would go that route if doing this kit. Before I started, I painted all the parts that were to be on the outside of the car
Lower torque box kit:
From inside the car, unplug the abs sensor plug that should be located on both sides by the quarter panel trim. With the sensor unplugged, push the rubber grommet that the sensor wire goes through, down through the floor. From under the car, unbolt the bracket that holds the sensor wires with an 8mm socket. Once unbolted, pull the wiring through the hole and set it aside. Next, ubbolt the bracket that is holding the ebrake cable which will be located right next too the bracket for the abs wiring
On SN95 Mustangs (96-04) you need to open up the hole that the torque box bracket goes into.
Once the opening has been made big enough, slide the bracket up into the hole and hold in place with a control arm bolt. (On the kit I got, I had to open the hole in the bracket big enough for the control arm bolt to fit.) There are left and right sides to the lower box kit. With the bracket held in place with the control arm bolt, the other 4 holes should be up against the floor. Using a 3/8" drill bit, drill from under the car through the 4 holes. From the inside, line up the 6x6 plate with the holes. (There are left and right of these also) Once the holes are aligned, bolt together using the supplied hardware that comes in the kit. The kit I got says to put the bolts up from under the car but I did it the other way with the bolts going down through the floor. That way if a nut happens to come off, your not driving over the 1 1/4" long bolt.
After the plate and bracket were bolted into place, I drilled a 3/4" hole down in the center of the bolt pattern. A 3/4" hole is big enought to slide the plug for the abs wiring through. Cut the rubber grommet off the wiring assembly and slide the wire up thought the hole. Plug the wire back in. Use silcone around the wiring to fill the hole.
The lower kit is now done.
Upper torque box kit
Drill a 1/2" hole straight up (at a right angle the sheet metal on the inside of the torque box) through the 1/2" hole that is already in torque box. The inner hole on my car was more of an oval so if yours is also, dont start with that one.
After the hole is drilled, put the torque box bracket in place and slide a 1/2" bolt throught the floor and have someone hold it there. From the inside of the car, slide the cruved floor plate over the bolt. Put the angled spacer over the bolt and snug it down with the supplied nut. With the plate snugged down, drill the other 1/2" hole the same way you did the first one. I used a unibit to inlarge the holes in the floor slightly to better align the curve floor plate. Put another bolt in the second hole and snug that one down the same way you did the first.
Have someone hole the bottom of the curved floor plate with a pc of wood so it is tight against the floor. I cut a piece of wood so it would hold the plate tight. From under the car, drill the 2, 3/8" holes that are in the front of the bracket. Bolt in place with the supplied 3/8" bolts.
Tighten all the bolts up but dont tighten the 1/2" bolts to much or it will start to suck the floor down.
If you are going to weld the floor plates in place, trace around the outside of the plates and remove them. Now take and remove the paint along the lines that you just made by tracing the plates. Bolt everything back in place and weld the plates to the floor. After everything is welded, paint the exposed welds and plates to prevent rusting.
Reinstall the rear seats and the rear axle assembly and you are finished.
If you have any questions or if you know I forgot anything, please let me know
Edit: thanks to caspergt for informing me before hand to get a long 1/2" drill bit for drilling the holes
