Not 100% sure. Hollander lists that as a break year. It could simply be different sensor types when they did the upgrade in 98. I know they beefed up the M5OD-R1 to an M5OD-R1HD around 2000 because of multiple failures behind the 4.0.
OK - did a bunch of digging. Ford says the difference is where the speed sensor is. That on 97s the OSS is on the rear differential, 98 and later it's on the transfer case or extension housing. The sensors show different signal types as well so it isn't a matter of just changing the wiring as the TCM won't understand the different sensor.
Wednesday, June 7th, 2017 AT 9:55 PM