Final drive fluid test?

[Doyt W. Echelberger]

Is there a way to test the final drive luid in an automatic transmission, 
to know if the seal between the diff and tranny fluids is leaking?

I have a chance to buy a 1991 200 FWD (150k miles) that has been 
fanatically maintained, with complete records. The only problem is a tiny 
leak of tranny fluid onto the floor under the transmission....a few drops 
overnight. This is clear reddish fluid. The leak did not exist a year 
ago....it is a new thing. This worries me greatly.

THIS CAR'S HISTORY: Two years ago the car had a complete change of final 
drive fluid and tranny fluid, as well as tranny fluid filter. The tranny 
fluid that came out was very dirty.  The new final drive fluid was synthetic.

PERFORMANCE: The tranny sounds good and shifts well in every direction at 
every speed and temperature.

ARCHIVE SEARCH RESULTS: The 200 automatic transmission has a long history 
of being a weak link in the power train. I have a dozen archive files 
relating horror stories about cars eating 3 automatic trannies; repairs 
taking a year to accomplish; only available trannies being new transaxles 
complete; rebuilds if anyone will risk it costing $3,000; No one wanting to 
even offer rebuilds; etc.

QUESTION: Anybody have any way to test to see if the tranny fluid is 
already leaking into the final drive? Seems like you would have to remove 
some final drive fluid and test it somehow,

Doyt Echelberger
happy owner of a 5ktq with manual transmission