Try Power Services Supplement. It is a good additive if you are looking for lubrication. You can find it at Wal Mart's, Auto Zone and Tractor Supply. Wal Mart and Auto Zone sell for $9.99 for 96 ounces. I believe tractor Supply is actually cheaper, but i have not bought any from them as of yet.
Also, this should not cause any problems since you have high mileage on your car. I would definitely recommend using PSS in place of tranny fluid. Johnny
1986 300SDL 173K
1985 300D [sold]
1996 Explorer 62K