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Discussion Starter · #1 ·
Hey all new to the site, and I have a question about those crappy torque boxs on my 91 coupe. I've been hearing a popping sound when I back out of my driveway and was told by a friend to look for cracks on the rear upper and lower torque boxs. Yup the passenger side lower is cracked. My question what is the best way to repair/stiffen this area.?Thanks
 

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weld around the seems.

for added support, several companies make braces you can add to the mix commonly known as "battle boxes"
 

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I've never exprienced torque boxes, where is the torque box located?
 

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yea mine got so bad that it destroyed the braket and i sold the car because i couldn't figure out how to solve the problem. the internet sells aftermarket brakets that you can weld right to the body to fix your problem
 

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Why weld them up ? Just so they can split in another place. They dont just crack for no reason. There has to be a reason. I found my control arms to not be moving on mine. I had splits on both sides. Replaced the control arms with both upper and lower. then welded steel plates to reinforce them.
 

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grease the bushings??

They crack from the stress of launching the car hard at the track or just from 100,000 miles of driving. All the back and forth flexing causes them to break like flexing a soda can back and forth.
 

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My torque box itself did not crack but the metal between the torque box and the outer body did. It looks like it was being slowly ripped and there is a 0.75 inch crack right now. That area is not rusty or damaged from previous jack stand use either, this is a simple fatigue failure from a repetitive stress (like Ryan stated with the soda can). For my situation, who knows if welding around the torque box would have prevented this. Maybe it would have transferred more stress to the inner side or prevented the whole thing from twisting all of the time.
Either way, I bought the upper and lower reinforcement kit from Laurel Mountain Mustang and it will be installed very soon.

The picture is not my car, just an example showing where mine is tearing except on the passenger side.
 

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the torque boxes are were the rear lower control arm attachés to the body of the car you need to remove the lower control arm and inspect the area clean it with break clean and a wire brush, look for stress cracks and also if the hole that the bolt goes threw is ovaled that will cause the crecking sound when you go from rev. to forward you can buy plates to strengthen the Boxes up but if they are too far gone then you might as well sell the car i seen the boxes replaced and the kid paid like 1500 and the car never drove straight its up to you what you wanna do but don't sleep on this i had a rear just about fall out one of my cars because i did not fix the boxes and i kept beating on the car
 

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also if you are new to owning a mustang the first thing you should do to the car before any performance mods is have sub frames installed and have the torque boxes done up this way the car will stand up to abuse especially if its a 5 speed
 

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My torque box itself did not crack but the metal between the torque box and the outer body did. It looks like it was being slowly ripped and there is a 0.75 inch crack right now. That area is not rusty or damaged from previous jack stand use either, this is a simple fatigue failure from a repetitive stress (like Ryan stated with the soda can). For my situation, who knows if welding around the torque box would have prevented this. Maybe it would have transferred more stress to the inner side or prevented the whole thing from twisting all of the time.
Either way, I bought the upper and lower reinforcement kit from Laurel Mountain Mustang and it will be installed very soon.

The picture is not my car, just an example showing where mine is tearing except on the passenger side.
Mine tore in the same place. I used the laurel kit and mig welded all the way down the crack. So far they have been good.
 

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Discussion Starter · #12 ·
Thanks for the responses I have had this car since new currently 62,000 miles garage kept. Already have all the other structural reinforcements hopefully I can get this taken care of soon, thanks again for all the info. Be safe and be fast.
 
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