Why could a complete flush cause problems in these transmissions? There are
many documented cases of high-mileage transmissions failing shortly after
having a complete fluid exchange. Why? If the unit has overheated (evident by
burnt fluid), the glue on the back of internal clutches has crystallized. When it is
soaked in a bath of fresh high-detergency transmission fluid, the glue on the
clutches dissolves, rendering the clutches, and thus the transmission, useless.
Therefore, on units with high mileage, it might be wise to change only the filter
and the fluid in the pan.
CVT Transmissions
Maintenance varies with the type of CVT. The best advice is to follow the
maintenance schedule dictated by the carmaker.
Standard Transmissions
Standard transmissions are not quite as touchy as the automatics; however, it’s a
good idea to have them checked every oil change. Standard transmissions use
one of three lubricants: automatic transmission fluid, 30W motor oil, or gear oil.
When checking the fluid be sure to check the level, the presence of moisture
(which renders the fluid a milky color), or the presence of wear particles. A
small amount of wear material is acceptable, but excessive wear material can
indicate a problem. The maintenance change interval for transmissions that use
automatic transmission fluid and 30W motor oil is every 50,000 miles. For gear
oil the recommended interval is 80,000 miles. Follow the carmaker’s
maintenance schedule because some can and do vary.