We investigated this when our van was new and finally learned that 2001 diesels could be changed out with a gear switch but it was impossible to fix 2001 gas vans....the Service Manager at the Ford dealer who sells vans to SMB West contacted Ford engineers, hoping to be able to reset the computer but it couldn't be done, at least at that time. I don't know if the gear swap is what SMB is doing now or not. And, yes, the odometer is also off. Our warranty will time out before it becomes null because of mileage so I don't worry about that.
I remember the first time we were driving off-road in 4WD right after we got our van and shifted into Low range. We were following a trail description in one of the guide books in Canyonlands NP and soon the waypoints seemed way off. I finally looked down at the speedometer and realized that the speedometer showed that I was driving at around 15-20 mph while I was actually just crawling along. Obviously, the odometer and speedometer were on the engine side of the transmission and not the output. There are probably electronically controlled by the RPM and gear setting....I'm old enough to only know about cable-controlled speedometers. <g>
'01 Ford EB50p Quigley 4WD