Hey, I hope this isn't breaking the rules here, but I'm part of a Crown Vic/Grand Marquis owner's club, specializing in the "box" body cars (79-91). If you go to Grandmarq.net, there are guys who spend most of their time working on cars like yours. They'll be able to help you out.
You do not have the problematic type of TV cable arrangement, those were 87 and up. However, the TV cable you have is still VERY sensitive to adjustment. Also, if you have a general lack of power, this will throw things out of whack because you are giving it more throttle than it should need, resulting in harsh shifts. On a carb'd car, improper idle adjustment (or adjustment without also adjusting the TV cable) will mess with shifting as well.