This is from an 89 grand marquis. I'm pretty sure its a 3-speed trans. It shifts in to one and two fine, then it shifts out of 2 but wont go into 3. after coasting to 40 mph it will go back into 2. It did it all the sudden one day. Any clue what I am looking at here?

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1 5/8 Hooker Competetion Headers, custom y-pipe,no cat, modified Flowmaster,Edelbrock open filliment filter with K&N filter in it
160 stat, BF G-Force w-rated tires, Hurst dual gate shifter

 

That would be a four speed transmission, the AOD or Automatic Overdrive. I can't say that I have heard of that complaint but as for not going to third the Direct clutches (on in 3rd and 4th) are the weak point in this tranny so I wouldn't be surprised at all if they were burned out. Just for grins though check the TV Linkage (goes from the throttle body to the tranny) loking for worn out sloppy bushings. Maybe you will get lucky. OH, by the way the setting is critical on these. They can feel OK and burn up the tranny if off.