Last week we examined the idea of performing an engine flush and found that in most cases, it is not a recommended procedure. When it comes to transmission flushing, the opposite opinion is true. Most technicians will tell you that a properly performed transmission flush will prolong the life of a transmission, and in some cases, even cure some early signs of a transmission problem such as minor slipping on pullout or sluggish upshifting.
The first type of transmission maintenance is the basic fluid level check on cars with a dipstick. Most cars need to be checked with the engine warm and running with the transmission in park. The reason for the engine and trans being warm is because transmission fluid expands as the temperature increases. Check either on your dipstick or in the owners’ manual as to the instructions for your vehicle as some cars need to be checked in neutral, and Hondas need to be checked with the engine shut off. There are two important things to observe when you check your fluid. The first, of course is the proper fluid level, which should be at or very close to the full mark. If near or below the add mark, you need to add the appropriate type fluid for your vehicle. Also observe the color and condition of the transmission fluid. It should be a reddish color and it may have some small bits of black particles in it as the clutches wear. If the fluid is brown, smells burned, or has metallic particles in it, these are signs of problems.
One of the things to know on late model vehicles is that in many cases the manufacturer no longer installs a transmission dipstick, leaving some people to believe that the transmission no longer requires regular maintenance. This is actually quite false. While some vehicles have a sensor, which will indicator trans fluid condition and level on the info display similar to an engine oil indicator, others give no indication. It is true that synthetic trans fluid lasts longer than the older traditional fluids, it still will break down and become contaminated over time and should be changed. Therefore, trans fluid checking and servicing has now basically become a dealer controlled maintenance item unless you are able to locate the fill level plug to check it.
Ultimately, your owners manual will tell you what transmission servicing is recommended for your vehicle. It will give you a schedule of recommended fluid changes, often between every 24,000 to 36,000 miles. If a transmission flush is recommended, it will probably range between 60,000 and 100,000 miles, while some manufacturers will not recommend flushing at all.
Opinions vary greatly as to whether or not this process is necessary for proper vehicle maintenance. Yes, flushing a transmission assists in removing dirt from the torque converter, valve body, trans cooler and cooler lines, but is it really beneficial to an engine? An article on Wisegeek.com reflects that some automotive professionals report that regular flushing assist with better working and longer last transmissions. However, the same article notes that many feel that flushes are unnecessary and can damage a vehicle’s valves and seals.
On most vehicles, it is still possible for a
mechanically inclined person to do a fluid and filter change, and this is
definitely better than no servicing at all. The first thing you should do is to
either pull your vehicle up on servicing ramps or jack the vehicle up and place
it securely on jack stands. If there is a drain plug, remove the plug and drain
into an appropriate drain pan. If no plug is present, or after draining,
carefully unbolt and remove the transmission pan, allowing it to drain into
your drain pan. Look in the bottom of the pan to see if there is any dirt,
sludge or metallic particles. A presence of large amounts of deposits is a sign
of developing problems. Clean the inside of the pan, remove the old gasket and
set aside. Now remove the filter, more fluid should now drain out of the valve
body, and dispose of the old filter. Install a new filter, a new gasket and
reinstall the pan. Estimate how many quarts of fluid that you have drained and
add slightly less than that amount. Lower the car to the ground, start the
engine and run until warm. Move the shift selector through all positions and
place back in park. Check your fluid and add as necessary to bring up to the
proper level. Drive the car about fifteen minutes and then recheck and add
fluid if needed. While this process does not remove all the fluid from the
transmission, it does serve as a great benefit.
When using a
transmission flushing machine, more of the old fluid is removed, and the overall
transmission system is cleaned. This means that there is less dirt and old
fluid to contaminate and weaken the new fluid. In some cases, a special transmission
flushing chemical is added to help clean the system before the new transmission
fluid is added. The fresh transmission fluid means that the transmission should
run cooler and more efficiently, thereby prolonging the life of the
transmission.
The only way a
transmission flushing machine will damage your transmission is if a high
pressure back-flush type machine is used to force fluid backward through the
transmission. This type of flushing system is hardly used anymore. In most
cases, a transmission flush does not rely on pressure to flush out the residue
of the old fluid. Instead, the transmission's pump or a machine is used to
gently circulate the new fluid through the system either by connecting directly
to the transmission pump or into the transmission cooler lines and follows its
normal path of circulation. This means that rather than applying pressure that
could damage the transmission, simple replacement is used to rid the system of most
of the old fluid.
There are two
slight drawbacks to the systems that connect to the transmission cooler lines.
First, is that unlike the normal transmission circulation path, this pushes all
the fluid through the lower pressure regulator which controls the internal
system of the transmission, it will not direct fluid through the higher
pressure regulator to the torque convertor. This means that there will still be
some old fluid left in the system which will somewhat dilute the new fluid. The
other issue is that by not removing the pan, the filter will not get changed
unless you request it, and the technician will not have the opportunity to
examine the inside of the pan.
In general,
periodic transmission flushes are a good idea, no matter which of the two
current types of machines is used. But, there is one time that you definitely
should not do a transmission flush. If the fluid has a severely burned smell or
there is a collection of metallic particles on the dipstick, your transmission
has internal part damage and is probably very close to failing. Your
transmission just has not figured out that it should die yet, but if you flush
it, it will most likely fail almost immediately. Save your money for a
replacement transmission, because at some time, probably in the near future,
you will need one. This is one of the major reasons why you would want a
transmission flush to be performed by a qualified professional.
Portions of
this article were sourced from the Transmission Flushing article featured on www.wisegeek.com.
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