Installing Torque-To-Yield Suspension Components – UnderhoodService

Installing Torque-To-Yield Suspension Components

What do some ball joints, tie rods and suspension components have in common with engines? The answer is Torque-to-Yield (TTY) fasteners. TTY fasteners are mounting fasteners which are torqued beyond the state of elasticity and therefore undergo plastic transformation, causing them to become permanently elongated.

What do some ball joints, tie rods and suspension components have in common with engines? The answer is Torque-to-Yield (TTY) fasteners. These bolts and studs that stretch are becoming more common on vehicles not just under the hood, but under the car. TTY fasteners are mounting fasteners which are torqued beyond the state of elasticity and therefore undergo plastic transformation, causing them to become permanently elongated.

Some ball joints and almost all tie-rod ends use a tapered stud and hole with a nut on top to secure the stud to the knuckle. The 7-10º angled taper, along with a threaded stud and nut, lock the components together by tensioning the nut and stud. TTY ball joint and tie-rod studs have two advantages. First, they can weigh less and still apply the same clamping loads. Second, the clamping loads are more consistent and controllable.

TTY fasteners were first used for engine head bolts because they required less torque and the torque applied was more evenly distributed. This resulted in even clamping forces on the head gasket and less distortion in the block and head.

Some of the first TTY head bolts were used on bi-metal engines with aluminum heads and cast iron blocks. The same is true for suspensions; the first vehicles to use TTY studs used aluminum knuckles like on the Corvette. But, now these types of ball joints and tie-rod ends can be found on Buicks, Jeeps and Fords. Also, more bolts for shock mounts, bushings and control arms are now using TTY fasteners. They are also used in vehicles with cast-iron knuckles.

Identifying TTY Ball Joints and Tie Rods
The metallurgy and heat treatment of TTY bolts and regular bolts is different, and you can sometimes tell one from the other by their appearance. TTY ball joints and studs have an inset hex head at the end of the stud. This can be used when tightening to the specified torque and setting the torque angle.

Always make sure to check the service information to get the right torque for a suspension component no matter what type of fastener. If you see an initial torque spec along with an angle in degrees, it is a TTY fastener.

Installation
If a ball joint or tie rod is not installed properly, it could cause damage to the vehicle and the reputation of your shop. Even worse, it could cause a crash. TTY fasteners just add an extra step to the torqueing process.

TTY ball joints and tie rods are usually installed dry. Do not apply any oil, grease, assembly lube or sealer on the stud or tapered bore. The reason why is because lubricants reduce friction when a bolt is tightened. This actually increases the torque load on the bolt or stud, which may overload and stretch a TTY bolt too far, causing it to break.

Do not use an impact. Most impacts can generate twice the torque needed for the initial torque setting. If a TTY fastener is over tightened, it can stretch beyond its limits and break.  The increased torque can also cause the female part of the taper to crack as to much clamping force is applied.

Aluminum knuckles, upper control arms and ball joints can be damaged if not tightened using the correct procedure. Knuckles and upper control arms are aluminum and can be damaged if a torque wrench and torque angle gauge are not used. No matter if you go too tight or too loose, if you fail to use correct tools and procedures, you could be buying the customer a knuckle and working for free to install it.

Many ball joints may have an initial torque spec as low as 15-30 ft/lbs and torque angles are between 140º and 225º. Never guess or try to use your calibrated elbow; always look up the spec and use a torque wrench. The same procedure is also required for tie-rod ends. Also, make sure the washers on the studs are in good condition and installed in the right direction. If a washer splits or fails, it could cause a catastrophic failure.

Reusing TTY Items

Make sure you check the service information to see if a TTY ball joint or tie-rod end is reusable after it has been removed. Some manufacturers recommend a joint should be replaced, while others do not indicate if it should.

For the technician trying to avoid dealing with this conundrum, it may be better to remove the control arm with the knuckle or separating tie rods between the inner and outer shaft. It is easier and less expensive to sell an alignment than face the possibility of a ball joint replacement in some cases. 

You May Also Like

HVAC Sensors: More Than Just Temperature

When a driver sets a temperature in the control head of an HVAC system, what does it mean to the vehicle? Seventy-two degrees could mean many different settings depending on the outside temperature, humidity and even the position of the sun.

When a driver sets a temperature in the control head of an HVAC system, what does it mean to the vehicle? Seventy-two degrees could mean many different settings depending on the outside temperature, humidity and even the position of the sun.

When a passenger decides that 70 degrees is a better temperature for their zone, things get even more complicated. Automatic Temperature Control (ATC) systems require a complex array of internal and external sensors that include ambient air temperature sensors, interior temperature sensors, outlet duct and evaporator temperature sensors, pressure sensors, humidity sensors, blend door position sensors and sunload sensors.

Nearly 5,000 To Participate In Auto Value, Bumper To Bumper ‘Festive Walk’ To AAPEX 2018

On Thursday, Nov. 1, nearly 5,000 Auto Value and Bumper to Bumper automotive professionals wearing matching yellow shirts will begin their “festive walk” from the Mirage hotel to AAPEX 2018 at the Sands Expo, temporarily shutting down the busy Las Vegas Boulevard along the way.

Drive Belt Checklist: What Are You Missing?

You might have only one chance to sell a customer a new serpentine belt. With belts lasting roughly 90,000 miles, proper inspection at the time of failure is critical not only for selling the belt, but also for ensuring add-on sales and better customer satisfaction.

VIDEO: Using Airflow To Sell Cabin Air Filters

Andrew Markel introduces an inexpensive tool that can assist in selling cabin air filter replacements. Sponsored by Auto Value and Bumper to Bumper.

airflow-selling-cabin-air-filter-video-featured
Air Conditioning Odor Causes

Air conditioning odors typically result from the uncontrolled growth of bacteria and other microorganisms in the evaporator. Research by independent laboratories has found fungi such as Aspergillus, Cladesporium, Penicillium and others growing on cooling coils and other A/C system areas.

ac air conditioning smells featured

Other Posts

Climate Control Modules

HVAC control modules may fail when the contacts and switches become inoperable. Sponsored by The Group Training Academy.

Paired Ride Control (VIDEO)

It’s always best to replace ride control parts in pairs. Sponsored by GSP North America.

Dorman Launches 300+ New Products In November

Among the new products is an OE FIX climate control module designed to fit 1.7M Chevrolet Express & GMC Savana vehicles.

Curing Springtime Air Conditioning Smells

Air conditioning scents can come from a host of things.