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Upper Control Arms & Improving Your 1994-2004 Mustang’s Suspension

Written By: Stanley Sadowski

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Before you go upping the power on an already fast Mustang, make sure you replace your weak factory control arms with an aftermarket set that was intended to handle the power your Mustang is putting down.

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Find out how much 1999-2004 Mustangs benefit from a set of upper and lower rear control arms. The SN95 Mustang is a great chassis that can handle some serious power, but one area that is in severe need of an upgrade are the upper and lower rear control arms.

American Muscle

What are Mustang Upper Control Arms?

The upper control arms are an essential part to the 4-link rear suspension of your 1994-2004 SN95 Mustang. They bolt up to the upper part of the differential housing and connect to the body. Their main purpose is to support the up and down movement of the rear axle. Under normal driving conditions the factory control are okay, but if you enjoy taking turns, occasionally hitting the track, or just want that extra piece of mind on the road then upgrading the Mustang’s upper control arms is highly recommended. 

Close Up of a BMR Suspension Control Arm End
Control Arm Bushing End with Grease-able Fitting

What Issues do Aftermarket Upper Control Arms Fix?

  • Fixs arc of travel
  • Prevents binding
  • Allows more control
  • Increases launch-ability

When you take a hard turn the stock upper control arms are notorious for binding which makes handling unpredictable. Binding is when the rear axle winds up or twists unaccordingly to the body of the car. This also prevents your tires from achieving complete traction. This is also a leading cause of snap over-steering. Snap over-steering occurs when the vehicle transfers weight during a turn and unexpectedly snaps in the opposite direction due to binding. It's extremely hard for a driver to correct, not to mention highly dangerous. Upgrading to a good set of upper control arms will give you faster launches, lower 60 foot times, improve handling, and tighten up the rear suspension by preventing snap oversteer.

2000 GT Mustang at the Track

What Aftermarket Upper Control Arms Are Out There? 

When in the market for a new set of upper control arms there are a decent amount of options out there. Adjustable upper control arms can be very helpful. They allow you to adjust your pinion angle in a matter of minutes which is important to a racing enthusiast. There are also a couple different styles of bushing and ends.

BMR Suspension Adjustable Mustang Control Arm
Adjustable Control Arm

Rubber vs Poly-Urethane Bushings

While the metal construction itself is stronger in aftermarket upper control arms, the bushings used are not too much of an improvement. Rubber and poly-urethane bushings still allow the rear end to bind under harsh conditions, but they will add some comfort and predictability to your Mustang.

Protane Mustang Bushing Set
Polyurethane Bushing Set for 1999-2004 Cobras

What are Spherical Ends?

Instead of using a big bushing, spherical ends (also referred to as Heim joints) use a small metal ball that pivots inside the joint. This allows the control arm to move multiple directions simultaneously. This style end also eliminates some of the rear axle binding. Spherical ends are recommended to someone looking to get the most out of their Mustang at the track. All of these designs are adjustable as well.

SR Performance Mustang Spherical Control Arm Ends
Spherical Ends

Alternatives to Aftermarket Upper Control Arms? 

To truly get the most out of your Mustang’s suspension, I would recommend going a step above a new set of upper control arms. A panhard bar or a watts link are two designs that answer many of the problems associated with a 4-link rear suspension by providing added stiffness and support. Panhard bars didn’t come standard on Mustangs until the year 2005, but were introduced to prevent many of the issues Mustang owners had complained about in previous model years.

Both of these designs center the rear axle with the middle of the car to help prevent axle binding or unwanted lateral movement. Considering the poor design of the factory lower control arms, a panhard bar or a watts link will reduce body roll and give you added traction when cornering.

BMR Suspension Adjustable Mustang Panhard Bar
Adjustable Panhard Bar

Benefits Of Adjustable vs Non-Adjustable Suspension

There are benefits and drawbacks to using adjustable control arms rather than non adjustable. While both perform exceptionally well, non-adjustables have 0 room for manipulation. Non adjustables work fantastic on a car at the stock ride height simply looking for a little more traction. However, if a Mustang is lowered, having adjustable upper control arms becomes much more important.

They allow for the correct adjustment of the pinion angle on the drive shaft. The pinion angle needs to be adjusted when lowered, something a non adjustable can not complete. This not only will provide more traction with the correct angle, but also increase longevity by maintaining proper wear and tear on seals and the drivetrain as a whole.