Lower Torque Box Reinforcement Information

Two many times I have seem post of people wondering how and what is involved in reinforcing the torque boxes. Although allot has not been posted about this modification on the web I have gathered what I can and posted it here for fellow Mustang enthusiasts. What I have found out is that the kit can be fabricated by anyone possessing good mechanical knowledge and of course a welder and means of cutting the metal. To build your own torque box reinforcement plates download the following ZIP file. This zip file have measurements and images of what each piece looks like. A fellow Mustang enthusiast (Chris) posted the following instructions for installing the torque box reinforcements. These instructions can be used to install your custom made torque box reinforcements.

Lower Torque Box Reinforcement Template and Installation instructions

Below are the instruction for installing the toque box plates and a few pictures I have collected of the install.

 

Battle Box Lower Torque box reinforcement: Installation instructions
written by Chris

There are several methods to reinforce the much abused and often damaged torque boxes of Mustangs (and similar Fox-bodied vehicles), but this is one of the easiest…While they can be used as bolt-in items, it is highly recommended that you have the units welded in to realize the full benefit of installation. The large inner plate meets NHRA requirements for roll bar or roll cage attachment points (minimum 6" x 6" x 1/8" thick). Due to the coverage of not up to but over the frame rail, this plate allows a down tube to be installed directly over the frame rail centerline, increasing structural integrity and safety.

Battle Box Packing list:

Required tools:

Installation procedure:

Remove the rear seat bottom from the vehicle by pressing the cushion towards the rear of the car while simultaneously lifting up. Remove the lower cushion retaining brackets with appropriate equipment. From underneath the car, loosen the lower control arm (LCA) fastener, and remove the nut. Install the correct bracket in the appropriate side (side specific LCA hole location), through the large opening in the sheet metal outboard of the LCA (Note: it might take some time to get them in place, as orientation is key to a successful installation. I’ve found that rotating the bracket so one "leg" is pointing forward (90 degrees from "normal"), and angled up 45 degrees, makes it quite easy to get "into the box".). Once inside the box, slide the bracket over the LCA fastener, install the nut, and finger tighten (Note: due to factory sheet metal variations, the LCA hole may have to be opened up a bit to allow installation. It is recommended that you not exceed 9/16" hole size, as this affects fastener contact area.). Mark the outline of each bracket inside the boxes, and the four fastener locations on the top of each bracket. Remove the brackets, and grind/sandblast the undercoating, paint, and galvanizing 1/2" or so on both sides of the marked line (I find sandblasting to be the quickest, easiest, and most effective method to do this.). Drill as many of the holes as you can from the bottom, using an 11/32" or 3/8" bit. If you find limited drill access on one or two fasteners, that’s fine; drill as many as possible. From inside the vehicle, locate the inner plate using the drilled holes, and drop fasteners in from the top, temporarily. The chamfered (angled, clipped) corner should be oriented to the rear and outside of the vehicle. If you are short any fastener holes, drill them using the inner plate as a guide. Mark the plate profiles on the floor, on both sides (including the three 3/4" holes on each side for plug welding). Remove the plates; scrape the undercoating/sound deadener, and grind the paint and galvanizing 1/2" on both sides of the marks. The car is nearly prepped for welding…

Before doing any major welding on your vehicle, it is important to isolate the alternator, computer, and all other high dollar electronic equipment from the chassis. Isolation prevents a voltage spike from damaging sensitive equipment by eliminating ground-fault loops. Disconnect the negative battery cable, the EEC ground (and EEC connector, for good measure), and any other grounds you might deem necessary. Some people don’t consider this step vital, and have gotten by without it. Personally, it’s worth the few minutes of labor to avoid several hundreds (and possibly thousands) of dollars of damage; I recommend you do it…

Since the brackets cannot be painted after installation (or at least the backsides), paint the entire bracket with a good quality paint or primer, and let dry (you might clean them first with lacquer thinner or carburetor cleaner first). Also, paint the backsides of the large inner plate. Grind the intended weld areas, and install the brackets into the torque boxes as before. Install the inner plate, aligning with the fastener holes in bracket. Install a flat washer on each fastener, and drop them through (from inside the vehicle; fastener heads will be located under the seat) the plate and bracket. Once all eight (8) fasteners are in place, have an assistant hold the bolt as you install a flat washer, lock washer, and tighten the nut (or vice-versa!) from underneath the vehicle. Torque the 5/16" fasteners to about 17 ft-lbs. Torque the LCA fasteners to 80-105 ft-lbs.

Once securely fastened, drape fireproof cloth over the side panels inside the car, and cover the glass with cardboard (or other suitable material). Weld splatter pits glass very easily, and seems attracted to it. Weld the inner plates completely around the perimeter, skip welding in 1/2" increments. The floor pan is thin, so proceed with caution and pay attention to the weld bead. Note one exception: The straight edge, closest to the drive shaft tunnel, is designed to fall directly on top of the inner frame rail lip. This seam can and should be welded as hot as possible to try and "burn through" to the lip. In fact, it might not be a bad idea to cut through the floor sheet metal with a grinder, cut-off wheel, or Dremel, to gain direct weld access to the lip. Continue skip welding, alternating plates and location, filling in the un-welded areas, until the entire perimeter is complete (appears as a continuous bead). The three 3/ 4" holes In each bracket for plug welding are located directly above the centerline of the LCA; they too should be welded as "hot" as possible for maximum integrity. From underneath the vehicle, weld as much of the bracket as possible inside the torque box. Take some time and try to at least complete the bottom seam, and wrap the corners as much as possible. Grind welds as required, and let cool. Prime, paint, and reassemble the vehicle, reversing the disconnection order.

  A couple of notes here: on the ‘early’ cars (’88 or earlier; not clear on date), the t-box and the frame rail are on the same horizontal plane; makes for easy boxing plate fabrications. On the later cars, the box is approximately ¼" LOWER than the frame rail, so you have to make a couple of bends in the plate to get the offset.

 


Here is a picture of the plate that reinforces the lower control arm torque boxes.


Here is the area where your LCA bolt goes. Notice how it was reinforced.


Here is a picture of the upper control arm torque box reinforcements.