I have a 2004 Subaru Impreza WRX with 212,000 miles. I have some paperwork on the past history of the car, but I don't see anything that refers to the transmission oil being changed (The transmission is automatic). I have had the head gasket replaced recently and the engine is in great shape. I am a little concerned, however, about the transmission. Is it okay to change the fluid after so many miles? I still need to check the color of the fluid, but baring a burnt mess, will the transmission handle a fluid change? My hope is to keep driving this car for a while, so I want to make the long-term decision here.
If this were my vehicle, I would change the transmission fluid and filter. There is a baseless school of thought, more like an "old wives tale" that you will just cause damage by changing the fluid in an automatic transmission. But that is just a myth!
ATF is oil and oils break down over time, particles get into it from the mechanisms in the unit and will clog up the filter. After 212K miles that oil has done it job, now retire it and get some fresh fluid and a clean filter in there.
This has the risk (albeit a small one) of making your transmission quit on you. Changing the fluids won't damage anything per se, but since the trans has 200k+ miles on it with no documentation on it ever having been serviced, the internals may be worn out and the only thing keeping it running may be the filth.
Kind of like when you buy an old car where the coolant in the radiator was never flushed and replaced. There may be pinholes all over it due to corrosion, but the sludge inside it is preventing leaks. When you flush it out, all of a sudden it starts leaking.