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How To: Install Mustang Upper Torque Box Reinforcements (79-04)

Posted 3/22/2016 by Phillip Perez

Increase the traction and stiffness of your Mustang's rear end with a upper torque box reinforcement kit.

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Upper Torque Box Reinforcement Kit

This particular upper torque box reinforcement kit is manufactured from eleven gauge steel, so it will add plenty of beef to those aging, factory torque boxes. They will feature bolt in installation for those that really aren’t going to launch the car hard anymore. However, I do recommend welding them into place to further maximize the strength of the reinforcements. If welding will be your go-to method on getting these torque boxes installed, make sure you grind the area clean before you weld and then apply some sort of rust prohibitive coating. On flip the side, if you plan on bolting these in, be sure and paint the brackets and support plates prior to assembly.

Required Tools

  • Jack
  • Jack Stands
  • Drill
  • 1/2" Drill Bit
  • 3/8" Drill Bit
  • Body Saw or Cut Off Wheel
  • Socket Set
  • 3/8" Socket Wrench
  • 1/2" Socket Wrench
  • Rust Prohibitive Paint
  • Phillips Head Screwdriver
  • Welder (Optional)
  • Sanding Disc (Optional)
  • Razor Blade
  • Putty Knife
  • Vacuum
  • Wobble Socket
  • Safety Glassses

Installation Instructions

  1. With front wheels securely blocked, raise rear of vehicle to an adequate working height. Support chassis securely with jack stands.
  2. Slowly lower differential as low as possible (Be careful not to over extend factory rubber brake lines) and support securely with jack stands.
  3. Continue supporting the differential with a floor jack; remove the upper control arm front bolt.
  4. Remove both sections of the rear seat and scrape away any sound deadening material from the upper torque box area where the curved plates will sit.
  5. From under the vehicle, drill a 1/2” hole at a 90° angle straight up through the forward most 1/2” hole in the top of the upper torque box and through the inner floor pan.
  6. There are a left and right side torque box reinforcement plate, verify which plate is correct for the side of the vehicle you’re working with.
  7. Place the torque box bracket in place and have another person slide a 1/2” bolt up through the bracket while from inside the vehicle you install the appropriate curved plate over the bolt followed by an angled spacer then washer then nut and tighten lightly.
  8. From under the vehicle drill another 1/2” hole at a 90° angle straight up through the rear most 1/2” hole in the top of the upper torque box bracket and through the inner floor pan.
  9. Have another person slide another 1/2” bolt up through the bracket while from inside the vehicle you install another angled spacer then washer then nut and tighten lightly.
  10. Have another person hold the lower part of the curved plate against the body of the vehicle with a 2x4 from inside the vehicle. From under the vehicle drill the two(2) 3/8” holes at the bottom of the bracket and completely through the curved plate. Install the 3/8” bolt and locknut and tighten lightly.
  11. Tighten all bolts.
  12. If welding, remove all paint, dirt & oil from the surface with a grinder or sander and weld in place. Repaint the welded area with a rust prohibitive coating.
  13. Re-install upper control arm.
  14. Repeat on other side.


Installation Diagram

How To: Install Mustang Upper Torque Box Reinforcements (79-04) - How To: Install Mustang Upper Torque Box Reinforcements (79-04)