I have been noticing my automatic transmission is not shifting smoothly when acclerating and sometimes occasionally letting off the gas i checked my transmission fluid level and it was low about a week ago i topped it up with new transmission fluid and thought that might solve the problem. I checked the fluid again today and conpared the fluid in a paper towel New fluid vs what came off the dipstick and the fluid off the dipstick is brown and kind of cloudy should i do a transmission drain and fill? I have heard that getting a compleate flush at 170,000km might not be a good idea nd could possibly ruin the transmission. I dont have any service history on the car and the oil didnt looks so great when i changed it so i have a feeling the tranny fluid might not of been changed in a long time.

should i flush the transmission fully or do you think a sinple drain and fill would help? 

Drain and fill, could take 3 times to get all the old fluid out.    Safer than power flushing. Filter on the outside of trans is supposed to be lifetime BUT... if you change it only use an original one.

Drain > Fill

Pull the radiator trans coolant line, I use plastic tubing to run both ends into a gallon jug.

Start the Subaru, it will pump out the old nasty trans fluid.  When you have about 3/4 of a gallon turn off the engine, empty the jug, fill the trans with another gallon of fluid > Repeat until the fluid going into the jug is clean.  It usually takes about 3 gallons.

I'm sure it will be much better, then if you really want to improve your trans switch to Amsoil trans fluid.  It made a world of difference on my 2002 Impreza with 230K on it.

Throttle Position Sensors can have 'dead spots' in their range of travel - that can cause shifting problems.

 

can you manually shift the trans smoothly?