You PM'd me for more info so I'll share some more before headed out to the garage...
First off, the 4R44E/5R44E/4R55E/5R55E will share the same parts. There are differences, for instance the first digit represents the number of ratios, so your 4R55E has four forward gear ratios and the third and forth digit represent the "torque capacity" so the 4R44E will support roughly 440lb/ft to the input shaft and the 4R55E should support 550ft/lbs (not engine rated torque because we have a torque converter that multiplies torque also). Mechanically some hard parts will change such as the thrust bearings and planetary set on the 4.0L units are much stronger, but for any aftermarket parts I am going to suggest, the 4R/5R series transmissions all share the same parts. So a shift kit that says 4R44E/5R55E will still support your 4R55E.
The bare minimum I suggest is...
Go to Ford and ask about any TSBs for that year. Purchase the parts they recommend for correction. While there pick up your gaskets (the separator plate should have a bonded gasket to prevent blowout) and pick up a transmission filter. Then pick up an in-line transmission filter and about 15 quarts of quality synthetic fluid (I use AMSOIL) to flush the system when you're done.
Above and beyond...
An EPC solenoid is a worthwhile investment. I used a borg warner solenoid (improved flow and filtering over the Bosch design) but 96-97 solenoids did NOT have an inductive signature to provide feedback so you may want to find out from BW if their EPC will function as a "green filter solenoid" replacement. Otherwise purchase a new Bosch stock unit as the EPC is a high wear part that usually needs replacing around 90-120K miles. A Transgo shift improver kit (has directions, pretty straight foward) and pick up a sonnax increased ratio boost valve/sleeve. Most of these mods are replacing pucks, springs, a few spools and pistons mostly working on the "forward mod valve/boost valve" side of the VB. Then locate a large efficient transmission cooler. Since our transmissions have a thermostat, I like to run the largest cooler I can so that it maintains 150f degrees (when the stat opens) for reliability. Also, there is a double lipped seal to replace the seal in the low/reverse servo. I suggest that for cheap insurance also.
I would also like to add, the 4R/5R transmissions DON'T need a complete rebuild 75% of the time. When they slip, you take it into a mechanic and an idiot will just diagnose it as "complete rebuild". In fact, most of the transmissions probaly just needed a new separator plate gasket (the stock non-bonded gaskets will blow out between the circuits and cause loss of pressure) or the EPC solenoid sticks (which controls pressure). Its quite unfortunate that shops will charge $2000+ for a rebuild when $200 in parts could restore or improve previous performance.
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