I recently bought a 97 superduty e-350 15 pass van with a 7.3. Well come to find out it started life as a 5.4. I was not aware of this. It has the engine/trans/computer/ instrument panel from a 2002 with 206K. It has the electric lift pump zip tied underneath. It ran good but some elect didn't work like power locks, int lights, mirrors, brake lights.
It looks like they changed the dash harness and it must of not been power because the wiring don't match at the kick panel plugs. This is a real Junk Yard Dog. AC and cruise worked.
The more I look everything is loose, even the nuts for the motor mounts were on 1/2 way finger loose ( I swear) They set the brake/tail lights with the double sockets/seperate blinkers like the 1994 style and cut a spot in the tail lights for the bulb. Weird so now my trailer lights are screwed up.
The rear is a 3.55 and my speedo is about 15mph slow at 75. The donor prob had 4.10's so how can I fix this. How can I tell if its a van motor or a truck. Or what turbo it has?
What kind of MPG are you getting with your swap before and after the chip?
I got a DiabloSport Predator Tuner but haven't even drove it yet either way to see MPG. Will this tuner give me more MPG?
My power locks are the only thing that don't work following the conversion. The donor van did not have power locks, so I know that its an issue with the harness. Probably not a hard fix, but I just haven't had the motivation to figure it out because I can live without power locks. That being said, all of the wiring connectors matched up between my van and the donor with the exception of one plug that connected behind the drivers seat under a plastic trim panel. Probably something to do with the rear speakers or door lights.
I also have 3.55's in mine and my speedometer is also about 15mph off (65 is really 80ish). I have a friend who works on diesels at a local Ford dealer and I've been meaning to have him fix it for me. Apparently its just as simple as plugging in the Ford scantool given to dealers and changing a code.
You can figure out whether its a van motor by looking at the International sticker on the valve cover (can't remember whether the sticker is on the left or right cover). It will have the year and horsepower listed on it, so just compare that HP number to the van and truck specs for that particular year.
I didn't pay much attention to MPG before adding the chip, as I chipped it like 5 days after doing the swap. Right now I'm getting 15mpg average, but that's always a mixture of interstate, in town, and trailer towing. If I burn an entire tank during an unloaded interstate run, I get around 17mpg running between 70-80mph. Towing a 4k lb 7x14 enclosed trailer at 75mph drops it down to 13ish.
As far as improving MPG with a chip, I don't know what kind of gains you'll see in terms of MPG but the gains in power will be surprising. I put a Superchips flashpaq on mine with a 4" straight through exhaust and it was a night and day difference in terms of power. That being said, I run it on the light towing tune because I'm worried about the EGT's without having an intercooler. I ran it once on the performance setting and the mixture of soot and tire smoke was impressive. Way too much fun, but not something I want to do without an intercooler. Hope this helps, and post up any other questions you may have.