TRANSMISSION LUBRICATION
Automatic Transmissions
Just like the oil in your car’s engine, the transmission oil (or fluid as it is known)
is subject to degradation from heat, friction, and dirt. Over time, degraded
transmission fluid can cause the transmission to fail. According to the Automatic
Transmission Rebuilder’s Association (ATRA), close to nine out of ten
transmission failures are caused by overheating and fluid contamination.
Automatic transmissions require regular maintenance according to the
Transmission Rebuilder’s Network International. The rule of thumb is to replace
the fluid and filter every 30,000 miles or once annually, whichever comes first. A
complete transmission transfusion is usually recommended.
This procedure exchanges all of the old fluid for new. There is one caveat here.
On vehicles with a poor transmission service history, seek the advice of a
professional before doing a complete fluid exchange. There are many
documented cases where a complete transfusion on transmissions with a poor
service history caused the transmissions to fail.
A poor transmission history means that the fluid is burnt (evident of
overheating) or that the fluid has been in the unit over 80,000 miles. Why do
they fail? If the unit has overheated, the glue on the back of internal clutches is
probably crystallized. When the unit is soaked in a bath of fresh high-detergency
transmission fluid, the crystallized glue is scrubbed clean, rendering the clutches
(and thus the transmission) useless. On units with high mileage, it’s probably
best to change just the filter and the fluid in the pan.