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.
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.
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.
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.
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.
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.
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. 
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. 
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. 
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. 
