Ford lovers are a fiercely loyal bunch with a lifelong commitment to the Blue Oval. They love Ford for its rich history, and yet at the same time condemn Ford for some of its notorious engineering efforts. Ford did its share of design work with budget in mind—such as upper control arms void of grease fittings from the factory that ultimately doomed shock towers from the start.

Because Ford car buyers were unaware of this issue, they never anticipated the consequences.

Cracked and broken shock towers are common with the classic Mustang, Cougar, Falcon, and Comet primarily. Enthusiasts blame shock towers—however, this has never been the reason shock towers crack and break. Shock towers fail because upper control arm bushings have seized up, which has worked shock towers back and forth (known as “oil canning”) until they crack and fail. It is like bending a piece of metal back and forth until it snaps. When upper control arm bushings and shafts fuse together, the shock tower does all the flexing until it gives out.

Upper control arm bushings are a solid metal on metal relationship between the bushing, which is attached to the control arm, and the shaft, which is attached to the shock tower. Given adequate lubrication, they work quite well together. Because car buyers never gave any thought to upper control arm bushing/shaft lubrication, deterioration has only gotten worse with time. The bushing and shaft grind against one another until they become fused together to become one.

Once shock towers crack and break, they must be replaced with stronger aftermarket shock towers with proper reinforcements that will enable them to perform under the most grueling conditions. You may also add “big-block” reinforcements, which were used on big block and BOSS Mustangs. Scott Drake reproduction shock towers from Summit Racing are equal to original equipment and protected from corrosion with EDP coating for lasting corrosion resistance. As long as you keep upper control arm bushings lubricated, these shock towers will last a lifetime.

Shock tower replacement is not easy nor for the faint hearted. You will need to pull the engine because the shock tower and brackets are significant structural members that also support the engine and transmission. You will need a spot weld cutter, an assortment of drill bits, clamps, and a wire-feed welder, which can be rented. Of course, there are other tools you’re going to need.

Let’s get started…

a rusted, broken mustang shock tower
Cracked shock towers are dangerous. They become damaged from fused upper control arm bushings where the shock tower “oil cans” (flexes) from control arm movement and cracks. (Image/Jim Smart)
an impact gun being used inside a mustang shock tower
Carefully compress and remove the coil spring located on the upper control arm. (Image/Jim Smart)
removing coil spring from a vintage ford mustang
Never place any part of your body in the path of the spring. Uncontained coil springs are dangerous and can maim and kill. (Image/Jim Smart)
using a small punch on a vintage mustang fender
Spot welds are centerpunched dead center to ensure a clean cut with a spot weld cutter. (Image/Jim Smart)
removing a bolt from within a mustang fender
This requires a lot of patience because it is tedious and there are a lot of spot welds to cut. (Image/Jim Smart)
removing spot welds from a vintage mustang shock tower
Boring out spot welds is time consuming but the best approach. Do not be tempted to chisel the sheet metal apart, which will damage and warp the steel. (Image/Jim Smart)
a cleaned section of a vintage ford mustang fender
Bore the spot weld out through the base metal, but do not penetrate both layers. (Image/Jim Smart)
rusted ford mustang shock tower with welds removed
The shock tower’s factory spot welds have been drilled out—with some completely through the two layers of steel, which is not what you want. (Image/Jim Smart)
mustang shock tower with welds drilled out
Bore through the base layer only and separate the shock tower from the inner fender aprons. (Image/Jim Smart)
using an air chisel to remove mustang shock tower
(Image/Jim Smart)
using air chisel on a ford mustang fender shock tower
A chisel needs to be used to penetrate stick welds and stubborn spot welds. Take extra care not to distort the steel. You may also use a grinding disc to cut welds. (Image/Jim Smart)
a shock tower partially removed from a ford mustang
Once all spot and stick welds have been severed, the shock tower is removed into the wheel well. Mating surfaces will need to be cleaned up. (Image/Jim Smart)
a new ford mustang shock tower replacement part
Summit Racing has everything you’re going to need to get into new shock towers from Scott Drake. (Image/Jim Smart)
new control arms for a vintage ford mustang
While you’re at it, replace all front suspension components for solid reliability and alignment. Scott Drake upper control arms are fitted with 90 degree grease fittings for easy access during chassis lubrication. (Image/Jim Smart)
vintage ford mustang fender with shock tower removed
As you can see, mating surfaces are distorted from shock tower removal. (Image/Jim Smart)
using a hammer and dolly to fix sheetmetal
These surfaces are trued with a body hammer and dolly to get them ready for the new shock tower. (Image/Jim Smart)
using a hammer to repair bent sheetmetal
All contact surfaces must be perfectly flat. (Image/Jim Smart)
grinding spot welds flat
(Image/Jim Smart)
grinding Sheetmetal in a vintage ford mustang fender
Once mating surfaces have been perfected, clean up all contact surfaces with a rotary or orbital sander for clean welding penetration. (Image/Jim Smart)
new shock tower going into a vintage mustang fender
Contact surfaces have been dressed with weld-through primer for corrosion protection and paint adhesion. (Image/Jim Smart)
installing a new shock tower in a vintage ford mustang
The shock tower is fitted in place using 3/8 inch bolts and nuts for alignment purposes. (Image/Jim Smart)
replacement shock tower in a ford mustang fender
Properly indexing the shock tower means examining all points of contact beyond the six bolts topside. (Image/Jim Smart)
close up of metal inside a mustang fender
Make sure fitment is solid at the front frame rail at the bottom. (Image/Jim Smart)
punching marks for welding a mustang shock tower
Shock towers are center punched for the drilling of rosette (plug and fill) welding before installation. (Image/Jim Smart)
holes drilled in a mustang shock mount fender tab
(Image/Jim Smart)
bolts temporarily holding a shock tower in place
You will want to install all six shock tower rebound bumper bolts to ascertain perfect alignment. Use 3/8 inch bolts and nuts for your mockup, which is the size of the bolt holes. The bolts are temporary alignment tools to get the shock tower indexed with the inner fender aprons. (Image/Jim Smart)
welding clamps being used on a mustang frame rail
The pre-drilled shock tower is secured and all dimensions have been checked. Good to have tools on hand like these large-mouth locking clamps to secure your work. (Image/Jim Smart)
welding a shock tower into a vintage ford mustang
The pre-drilled holes are being rosette welded. (Image/Jim Smart)
shock tower getting welded into a vintage ford mustang
The shock tower has been welded completely around its perimeter. The rosette welded holes will be ground smooth to where they disappear. (Image/Jim Smart)
welding a shock tower replacement into a ford mustang
Underneath, these pre-drilled holes are rosette welded to the inner fender aprons and ground smooth. (Image/Jim Smart)
bracket being held in place by clamps in a ford mustang
(Image/Jim Smart)
drilling holes into a ford mustang shock tower replacement
The separate shock tower bracket, which will be welded to the shock tower, supports the lower control arm and engine mount. Weld holes are drilled into the bracket as shown. (Image/Jim Smart)
installing bolts into a replacement mustang shock tower
The lower shock tower bracket is affixed to the shock tower and secured with bolts used at the upper control arm mounting holes for alignment purposes. (Image/Jim Smart)
tightening bolts in a ford mustang shock tower replacement
You will want to use exact size bolts at these holes. (Image/Jim Smart)
frame mount for a replacement mustang shock tower
Long reach locking pliers, in addition to the bolts, are used to secure the bracket assembly. (Image/Jim Smart)
bottom of a mustang shock tower prior to welding
(Image/Jim Smart)
welding in a replacement ford mustang shock tower
Rosette welding is the chosen method to secure the shock tower lower bracket assembly. (Image/Jim Smart)
close up of welds on a new ford mustang shock tower
The view from underneath demonstrates the plug and fill (Rosette) welds at the shock tower and inner fender aprons. (Image/Jim Smart)

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Author: Jim Smart

Jim Smart is a veteran automotive journalist, technical editor, and historian with hundreds of how-to and feature articles to his credit. Jim's also an enthusiast, and has owned and restored many classic vehicles, including an impressive mix of vintage Ford Mustangs.