'00-'04 Warner 1354 w/o "shift on the fly"

[slvr00gt]

I am looking for the new transfer case for my 98 ranger 4.0l. The transfer case article below says that only difference between '98-'00 and '00-'04 is "shift on the fly". What does it mean in application to the t-case? Is it interchangeable with my ranger? I thought "shift on the fly" only applies to the vacuum hubs on my ranger

Also, parts interchanges list two models of t-case on 98 ranger: F57A-AA or F87A-AA. Based on the description I am pretty certain I have the later. Can I figure this out for sure based on the build date?

http://www.therangerstation.com/tech_library/TransferCases.html

1998-2000 (Electric Shift) rear circular flange, front cup yoke w/o speedo hole, w/o sensor hole,
2000-2004 (Electric Shift) rear circular flange, front cup yoke w/o speedo hole, w/o sensor hole, w/o shift on the fly

EDIT: I called ford dealer parts, gave them my VIN and they told me transfer case number. It is F87.

 

[hondaxr650]

The older case with "shift on the fly" has a magnetic clutch that spins the front driveshaft up to the same speed as the rear before it shifts to prevent gear grinding. The reason the later cases don't have it is because starting in mid 2000 they went to a live axle setup on the front so the front driveshaft is always being spun by the front axle and doesn't need the clutch to get it up to speed. If you have vacuum hubs, You'll need the shift on the fly case if you want to be able to put in 4wd while driving without damaging the gears. The shift on the fly case will have a single brown wire coming out the back of it, near the rear drive flange. It's the power wire for the electromagnet that engages the clutch.