1994 Lincoln Town Car auto transmission - some thoughts please? Thanks?

[thewrangler_sw]

As mentioned, this is a 1994 Lincoln Town Car, Executive model (automatic transmission, 8 cyl engine)...the car is dropping out of gear, into neutral. This happens whether the overdrive is on or off, but is not 'constant'....one trip, it will drop in and out of gear frequently, and another trip, it will do it only a time or two. Seems to do it worse when traveling between 45 to 70 mph, but I have noticed it in speeds as slow as 35.
Engine runs great, no stalling, no apparent loss of power, and no warning lights on the dash when this is happening.

I would think if it were mechanical problem it would be consistent, but I'm open to ideas. When it is 'acting up' it can be very very rough, or it can be almost nonexistent, traveling over the same road, same speed, etc.

Any help would be appreciated, and if possible, a link to a parts list.

Thanks All