David Stribling/DVS Restorations
August 1, 2002
Contributers: David Stribling/DVS Restorations

Step By Step

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Subframe connectors are a quick and easy way to add strength and reduce body flex in your ’65-’70 Mustang. We prefer weld-in style to the bolt-in style, as they add more rigidity.
Along with your welder, you’ll need the following tools: a grinder, a method of cutting 1/8-inch plate steel (Sawzall, cut-off wheel, plasma cutter, etc.), a wire wheel mounted to your drill or die-grinder to remove paint and debris from the car, two or three 6-inch clamps, and a square and marker. Don’t forget all of your safety equipment.
Since most of you don’t own a lift, you’ll need to come up with a way to get the car in the air so you can weld. We recommend using four car ramps, positioned so the car cannot roll off the ramps. Use a jack to get the car up, and put the ramps under each wheel. We recommend that you have the weight of the car sitting on the tires rather than jackstands on the framerails of the car.
Make sure the car is solid enough for this project. If the car is rusted in either the front or rear, repair those areas first. This is the front rail and, as you can see, we have plenty of room to attach extra bracing.
The same cannot be said for the rear attaching point, just ahead of the front-spring mounting point. There is only about four inches of room here.
Here’s a prime example of what can happen over a 30-year time span. Jacking has bent this area in, and it needs to be straightened before welding in the connectors.
It’s time to separate the men/women from the boys/girls. Many times, the floorpans sag down low and create a situation where a straight piece of metal doesn’t fit cleanly. You need to decide if you want your rails to ride low to clear the pans, or you want to trim the pans so the rail hugs the body better. The design of these rails allows for both options.
We decided to trim the pans so our rails hug close to the car.
The basic body of the framerails is two pieces of 2-inch square tubing purchased from the local metal dealer. Most places will cut these to the correct length for free or a minor fee.
We’re using 1/8-inch wall tubing. We’ve heard all the arguments for and against big, weighty rails being welded to 14-gauge sheetmetal, but we have several reasons for going with the big walls. First, NHRA says so for some types of chassis construction. Second, you aren’t going to flex these in the middle point. Third, it’s more readily available than other sizes, and most metal suppliers carry it in stock.
A piece of 1/8-inch plate steel, 1 foot square, takes care of the front bracing. You’ll need a way to cut this into little pieces.
Using the drawing, lay out the plate using your square and marker. The thickness of your cuts will depend on what you use to cut this plate, and will affect the fit when mounted to the chassis.
OK, we cheated. We used the plasma cutter with some homemade guides to make our cuts. If you don’t own one, get your spouse to buy you one; they’re great.
The small 2-inch-square pieces are used to seal the ends of the tubes and keep mice and road debris out of your connectors. Round off the edges of the ends with your grinder so they match the radius of the tube.
The end welded in place and ground for a smooth finish.
The rear brackets are made out of either 1-1/2-inch or 2-inch angle iron. We’re using 1-1/2-inch and using our cutoff wheel to make four pieces 4 inches long.
Using angle iron allows us to have some leeway when trying to get around floors and non-square rails.
For those super paranoids who think they’re going to bend a piece of 1/8-inch angle iron, you can add a couple of gussets in from each end to add strength to the bracket. Don’t weld them to the ends, just in case you need to trim the brackets shorter to avoid springs or other obstacles.
Mount the framerail using a 6-inch C-clamp. Your final mounting position will be determined by the straightness of the rails and floors. We like to run the rails up pretty far along the inner frame extension, rather than tacking them on the ends. Think of it like holding a baseball bat at the end rather than choking up with two hands.
The rear of the connector can be held in place by removing the floorpan drain plug and running a clamp through the hole.
Once you have the rail aligned front to back and it clears the spring with no problem, fit the front bracket by clamping the sides in place and checking the fit of the base. Remember, the thickness of your cutting device and the condition of your rails will determine the fit of these pieces. Once they’re flush against the inner rail and tight, tack-weld the two sides to the bottom plate and remove the brace.
Fillet-weld the brace and grind it smooth if you want.
Using your wire brush, strip the paint and coatings from the areas to be welded around the rails. If you have excessive undercoating, oil, transmission fluids, or road grime, you’ll want to really work to remove this, as it does tend to ignite.
Slide the front bracket back over the two rails and clamp in place. Make sure the bracket is flush with the inner rail, as there is a good chance the outer subframe connector is not at a perfect alignment with the body. Tack-weld the bracket to the subframe connector only, and remove the connector body.
We HATE welding on our backs, so anytime we can do it on the bench we do. Fillet-weld the bracket to the subframe connector. Note the rail position—yours may vary!
Here’s where we say these rails will adjust to your car—the angle iron not only allows us to weld to two separate planes, but they allow us to move the rail up and down or right and left to conform to the chassis layout. This layout shows the rail hanging down to clear the strengthening runners in the floorpan. If you want, you can go to 2-inch angle iron to add more area on the chassis side to compensate for the drop.
Here’s where the alignment ended up on our car. Notice it ain’t perfect!
One full-length subframe connector, ready to weld on the car. The fun is about to begin.
Reclamp the rail in place and fillet-weld along the seams. Repeat the process for the other side. These rails are ready to go, fit the car well, and are supported on two planes both front and back. A great weekend project that will make your car handle.

Ah, your loving spouse purchased a new welder for you, and you’ve succeeded in welding together every piece of scrap metal lying around the garage. Now, you’re looking for a useful project to put your newfound talents to work (besides the new lawn ornaments). How about a set of subframe connectors for your vintage Mustang? This article details a simple-to-build set of subframe connectors that adapts to your car easily.

As you know, the Mustang chassis is built on a unibody construction, which means it gets its basic structural rigidity from the sheetmetal parts being welded together to form the basic structure. The front framerail extension and the rear framerails don’t actually connect, but are tied together through the sheetmetal of the chassis.

Because of this, the Mustang has been given, by its detractors, the unwanted nickname of "The Hinge." Unfortunately, in performance conditions, this is true. For years, racers have been tying the front and rear framerails together and stiffening the flex in the chassis, thereby making the car handle better under performance conditions.

Before taking on this project, please read through the following guidelines and recommendations.

1. All measurements in this article are approximate. After 35 years of wrecks, rust, rebuilds, jacking mayhem, twisting, and other perils, there are very few perfectly straight Mustangs left in the world. If you bought a pair of the better aftermarket connectors and they didn’t fit, there’s a good chance it was probably the car and not the connectors.

2. Make sure the car to be modified is up to the task. Welding new connectors to rusty metal doesn’t help much.

3. Make sure YOU are up to this task. Don’t sacrifice your pride and joy if you can’t wield the welder. Take it to your buddy who can.

4. Remove the carpeting and anything else from the interior that will be close to the heat of the welding process. Interior fires are not pretty.

5. Make sure the fuel lines and fuel tank are temporarily located somewhere else, away from the welding area. They run right along the framerails, and they’ll have to be moved.

6. As a guideline, we like to weld in these connectors while the car is weighted down with the drivetrain and sitting on the wheels. If you lift the car in a place other than where it sits weight-wise, you may actually weld a nice bow right into your car (remember the reason we’re doing this is because the body flexes). Big-block owners, take extra note of this. If you don’t have a buddy with a drive-on-style lift, find another way to get the car in the air.

7. ALWAYS use all the appropriate safety equipment as recommended by the manufacturer of the tools you’re using.

8. Remember, you’re changing the characteristics of the chassis, and doing so may affect the way the car performs in a collision. By installing these, you’re assuming all the risk! Once installed, your Mustang should handle like a whole new car. Perhaps you can slalom around all those lawn ornaments you made last winter.