Undercar Inspection Checklist, Larry Carley, Tire Reveiw, August 1999
Unusual tire wear is a dead giveaway that a vehicle has either an alignment problem or worn or damaged steering or suspension parts. So anytime we check tires and discover abnormal wear,we recommend an alignment check and undercar inspection to identify the culprit. Replacing worn tires without finding out what's eating the rubber will not solve the problem because the replacement tires will suffer the same fate regardless of their treadwear rating or tread life guarantee.

Tire wear is usually one of the first symptoms that appears when steering or suspension parts are worn. What to look for:

Toe wear - A feathered wear pattern across both front tires, and sometimes shoulder wear on the inner or outer edge of both tires. Toe wear is usually caused by worn tie rod ends, but may also result from worn or loose inner tie rod sockets on rack & pinion steering gears. Other causes include bent steering arms or misalignment in the rear wheels.

Camber wear - Uneven wear on one side of a tire may show up when control arm bushings have collapsed, ball joints are loose, a spindle or strut is bent, or a strut tower is out of its normal position.

Cupped wear - This may be the result of badly worn shocks or struts, or wheel and tire imbalance.
Steering can be inspected one of several ways. A test drive will often reveal problems that may escape detection in the service bay. Things like steering effort, return, stability, feel and noise are impossible to check without actually driving a vehicle. So take a short test drive and take note of how the steering feels and responds.

Another way to check the steering is to do a "dry park" check. With the full weight of the vehicle on the wheels, have a helper rock the steering wheel while you look for play or looseness in the steering linkage and steering column.

Steering effort on both manual and power systems should be checked during the test drive or in the service bay with the weight of the vehicle on the wheels. Unusually high effort combined with poor steering return may indicate a weak pump or a worn spool valve in the steering rack.

Check the fluid level in the power steering pump reservoir. A low level may indicate leakage. A visual check of the pump, hoses and steering gear should reveal the source.

Check wheel bearings for play before proceeding on to the ball joints because play here can mimic loose suspension parts and contribute to steering wander and instability.

If the ball joints have built-in wear indicators, joint play should be checked with the weight of the vehicle on the wheels. Ball joints without built-in wear indicators are generally checked by raising the suspension to take the weight off of the joints.

Front control arms as well as rear trailing arms and lateral links should all be visually inspected for damage or cracks. Also, make sure the ball joint is securely attached to the arm.

Check bushings for excessive movement, deterioration, cracking or crush. This can be done by gently prying against the control arm to see if the bushings allow much movement. A little "give" with rubber and elastomer bushings is normal, but if you see more than about 1/8 inch it may mean the bushing has collapsed.

On sway bars, check the sway bar bushings and mountings. The mountings should be securely attached to the chassis, and the bushings should be in good condition (no cracks, splits, crushing, etc.).

A "bounce test" will usually reveal shocks that are badly worn, but a test drive will give you a more accurate picture of their condition. If the vehicle sways excessively, rocks, feels bouncy or otherwise lacks proper ride control, you should recommend new dampers.

Finally undercar inspection checking the following, too:

	Exhaust system for leaks or damage. Also, check for broken or missing hangers and heat shields.
	Boots on front-wheel drive and all-wheel drive axle shafts. A torn, loose or leaking boot will lead to failure of the CV joint.
Brake lines & hoses.
	Parking brake cable & linkage.
	Oil leaks (engine oil pan, transaxle or transmission and differential).
	Coolant leaks (bottom of radiator, lower hose & freeze plugs in the engine, if visible).
	Fuel leaks (fuel lines & tank).
	otor/transaxle mounts.