Porsche Repair: 944 transmission, atf cooler, automatic tranny

Question
Charles: my '83 944 runs like a dream (only 24K miles) but I want to flush and replace all the automatic tranny fluid. Can I do that by disconnecting the return hose from the radiator, starting the car with the tranny in park and adding fluid through the transmission in the rear of the car?? Thanks!! Norm

Answer
In my experience there are two things that will kill an automatic transmission, contamination and contamination.  Whether it is from old gummed or burnt ATF or metal particles from the trans itself.  
Although you want to get rid of both, in an attempt at doing that you can move the contamination from its sleeping place to a valve or to a narrow port or passage and block up the circuit.

So, I would stick with the factory manual on service:
With the trans "warm" and vehicle on level surface: at the trans oil sump, unscrew the filler tube and drain fill tank and sump. Remove sump and filter screen, clean and replace with new gaskets. Signs of metallic or plate particles in the ATF could mean spending a weekend to drop the torque converter for a drain and flush... hmmmmm.  

There is also a procedure to flush the ATF cooler and lines; by attaching a hose with adapter to return line and flush the cooler with ATF.

Reference: Shop Manual Section 38, pgs 38-2,a,b,c

Hope that helps you.