Ford Repair: 1986 Aerostar drive engage not, ford aerostar van, dextron iii

Question
Hi,

I have a 1986 Ford Aerostar van with a 6 cylinder and auto transmission which has been rebuilt but that was almost 9 years ago.

Anyway, I've had a slow but sure transmission leak on it and I found it a week or 10 days ago and it stopped leaking.  I filled it back up again but the Trans Fluid was - I think - Dextron III, which, I've since found out not for a Ford.  

So, I was driving down the highway last night and I had to stop by the library.  When I did I put the car in park and mind you there was no problem with the transmission except a little hesitation as it shifted into either reverse or drive.  As I got back into the car I put the transmission back into drive and it just sat there and would not shift into drive.  I did try reverse and it did shift into reverse so I backed it up and put it into a parking space and there it sits to this minute.

Do you think that it's all due to the transmission fluid?  I'm going to drain it anyway but it's hard to believe that it just quit like that usually something that's going bad gives you a little bit of warning beforehand.  

I think that's it. I'll look for your answer here and there.  This is the first time that I've used this service so I don't know how fast or slow you guys are. I expect it is dependent on how busy you are.

Thanks,

Joe

Answer
Hello and thanks for the question...I'll try to help.
The Mercon III that you used is fine for the A4LD transmission in your vehicle. Mercon V is the incorrect fluid and that has just come out in the last 4-5 years. I would check the fluid level and see if there is any debris in the pan at the time of your service.
Erik