I just bought a 91 Mercury Cougar with the 3.8L and the AOD. I have a few questions here as I am a nooob and all. My trans will shift into every gear with no slipping/hesitation except OD. When it goes to engage OD it will have a slip to it, but no other gear. The fluid looks like motor oil and I took it to a tranny shop to have it looked at. He said it wasn't burnt, it was just dirty. So what I am wondering is, would draining the transmission and refilling it and putting in a new filter fix the problem, or am I looking at getting a transmission? If that's the case, then what I would like to know is what vehicles with the AOD can I get the trans from? From what I hear, the 5.0 and the 3.8 share the same bolt pattern, so can I pull a trans from a 5.0 and install it in my car? One last thing I was wondering is what years can I pull the AOD from or does it matter? I have a 87 Lincoln Town Car that has the 5.0 and I know I can't use that one because of the tail being a different size, but I have a feeling that I am going to need a new trans if this doesn't work. Please let me know what will work. I have heard that the 5.0 transmission is a stronger one so I would think I could just drop one of those in vs the 3.8 trans. Any advice would be greatly useful.