Chassis and Suspension

Chassis Lubrication

Lubricate all steering and suspension joints with chassis grease. If the chassis parts are not equipped with grease fittings, you may be able to install them in some components by removing the screw-in plug. If a part doesn't seem to be taking any grease, wiggle it a bit. If this does not work you would need to replace the grease nipple. Continue pumping in grease until the dust cover of the suspension joints swells. Check the level of differential oil and manual transmission oil.

Differential oil and transmission oil levels usually are checked by removing a plug from the side of the unit. Most cars use hypoid type oil in the rear end. For most rear-drive cars, the tube that is used in the rear end is also used in the manual transmission.

Check your shop manual or owner's manual. Some of the new generation vehicles do not require to have the under chassis lubricated at all. Vehicles like the Maruti do not require under chassis lubrication. Only check for torn or damaged rubber bushings. While replacing the same you should use French chalk powder and not grease.

Under Chassis Inspection

Every time you have your car is up on jackstands for an oil change, you should perform at least a basic under chassis inspection. Check all exhaust system components for possible leaks or deterioration. Make sure all the hangers are intact and in good condition. Look for areas where the undercoating has fallen off or has been damaged. Remove any dirt, sand off any rust and recoat (paint) the area. Check all rubber bushings and dust boots for obvious deterioration. Pay particular attention to those bushings found at each end of front or rear sway bars, as well as those that hold the centre of the sway bar to the frame.

The bushings used on front and rear control arms are also potential problem areas. If bushings have shrunk or shredded, handling will suffer and in many cases the component will produce a lot of noise. Check engine and transmission mounts for looseness or cracking of rubber parts. A broken engine mount that allows the engine to rise up from its proper location can be more than an annoyance. In some cases it can make the throttle stick open.

Inspecting Ball Joints

Every 20,000 Km your under car inspection should include a check of steering and suspension components. Begin by checking ball joint condition. Cars with upper and lower control arms have both loaded and unloaded ball joints. Most mechanics check the condition of the loaded joints only. If these are okay, the unloaded joints should be okay as well. Of course, if the loaded joints have been replaced, they could be in better shape than their weak sisters.

The loaded ball joint is the one that carries the spring. If the spring is mounted on the upper control arm, then the upper joint is the loaded joint. If the spring is on the lower control arm, the lower joint is the loaded joint. To check a loaded ball joint for looseness, the load must be relieved.
On cars where the coil spring is mounted on the lower control arm, relieve the load by placing a jack under the control arm as close to the joint as possible
Check axial (up and down) movement of either type of joint by inserting a screwdriver between the bottom of the tyre and the floor, then lifting the wheel. The joint should allow the wheel no more than 0.05-in. free movement. You can measure axial movement precisely by mounting a dial indicator so its stem rests against the bottom surface of the wheel's knuckle. The stem must be parallel to the imaginary line that runs through the centre of both joints. However, most mechanics forego the dial indicator. If there's a noticeable amount of axial movement, it's probably well in excess of 0.05-inch.
If you're not sure about how much axial movement the joint allows, check radial movement by pushing the bottom or top of the tyre in and out. More than 1/4-in. of movement at the far edge of the tyre is excessive.

Front Wheel Drive

On front-wheel-drive cars, check all CV joint dust boots for visible damage. Generally, unless a torn boot is discovered immediately, the joint will have to be replaced along the boot, since CV joints that are not protected from dirt deteriorate rapidly. A sure way to diagonise a faulty CV joint would be to take a U turn at a reasonable speed ( about 20kmph) if there is a clicking or crackling noise heard from the suspension in most cases the joint would require replacement. Also there would be a metallic noise on sudden accleration and deaccleration, if the joint is faulty. Though there are repair options available these are not recommended by the manufacturer. In such cases it would be prudent to replace the entire assembly.

Shock Absorbers and Springs

Because they can cause a vehicle to handle erratically, worn springs and shocks can be as dangerous as they are uncomfortable. To check spring condition, you have to determine it the car's body and frame are as high above the rear axle and front spindles as they're supposed to be. To do this, you must measure ride height. Measurements are taken at each end of the car. The exact method varies, but usually you have to measure from a spot on the rear axle to a snubber or other component on the frame and from a point on the front spindle to a specific location on the frame or under-body. These measurements are compared to rnanufacturers specs to see if they fall in the acceptable range.

If not, coil springs must be replaced and leaf springs must be replaced or recambered. Once ride height has been corrected, wheel alignment must be checked. Shock absorber condition is best determined by the way your car behaves on the road. If it bounces every time. you bit a burnp or dips and sways as you corner, it needs new shocks.

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