Shock shifting into 3rd and slightly less into 5th when cold. Seems to shift perfectly when really warmed up. I'm second owner and fluid looks really dirty. Does the 6-181 5 speed AT in this car have a drain plug or not.

 

Dirty Oil OH NO! Sounds like original owner never flushed, drained or changed fluid ever! Automatic transmission fluid should be changed every 30,000 miles. ( Flush it or Forget it |*MotorWeek ).

I know Mazda has no schedule (I believe) to change tranny fluid on Mazda 6. That may be OK for highway driving only and less than 100,000 miles.

Also do yourself a favor and install an external tranny cooler:

"According to the Automatic Transmission Rebuilders Association, 90% of ALL transmission failures are caused by overheating".

"As a rule of thumb, every 20 degree increase in operating temperature above 175 degrees F. cuts the life of the fluid in half!
At 195 degrees F., for instance, fluid life is reduced to 50,000 miles. At 220 degrees, which is commonly encountered in many transmissions, the fluid is only good for about 25,000 miles."

My input: Guess what your rad temp water is: The OE coolant thermostat is 188 degrees and it usually runs hotter. This is why you need an external tranny cooler! My coolant temp gauge is 180 degrees.

"Example: ATF that enters the stock radiator cooler at 300 degrees F. leaves at 240 to 270 degrees F., which is only a 10 to 20% drop in temperature, and is nowhere good enough for extended fluid life. An auxiliary transmission fluid cooler is easy to install and can substantially lower fluid operating temperatures. The plate/fin type cooler is somewhat more efficient than the tube and fin design, but either can lower fluid temperatures anywhere from 80 to 140 degrees when installed in series with the stock unit. Typical cooling efficiencies run in the 35 to 50% range."

QUOTES FROM: How often should the automatic transmission fluid... — Yahoo! Autos

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