I had sporadic OD problems in my '85, so first thing when it was in the shop for a general inspection they found it to be low about a quart of fluid- they topped it up and then it was fine for a while. Not too long later it started having misc problems (mainly not going into OD even though the light came on) so I drained the fluid (while looked worse than old motor oil- who knows, maybe it was) and filled it with Valvoline type F ATF, and just in case it could help (what harm could it do?) I threw in one of the Valvolines high mileage ATFs with "leak-stop" and all those other great things they said it does (recondition old dry seals and o-rings, etc). Since I did that it's been shifting flawlessly (that was only about 4k miles or less ago)- well worth the few bucks the fluids cost- it was very easy to do too. To put the new fluid in I used a section of 1/2" black plastic water type pipe with an elbow on the end into the tranny and a funnel on the other end (coming up in the engine compartment)- I also drove the front left of the car up onto a car ramp so it was high up (read to do that on this board, so as to get the tranny overfull- again, seems to work great). Before going through rebuilding the OD I'd try something like this.