Speedometer Re-cal. Question.

[97e350]

I have a 97 e-350 SD van which was gas and now has a 2002 7.3 transplant. My speedo is 15 mph slow. Showing 60 at 75 mph actual. I have been searching and and still not quite clear.

I took it to the ford dealer and they said it was within 4mph and when I drove it there was no difference, Lol

So my question is can it be done thru the abs module with the auto enginuity alone? Or do you have to go into the PCM also. My tire is a 265/75/16 and stock is 245/75/16 so how can I be so far off. I have 3.55 rear and maby the donor had 4.10 is what I'm thinking ?? Is this affecting all my shift points? If you just let off the petal at 50mph the trany disengauges untill it hits 35mph on the speedo then engauges again like engine braking but I'm really going about 45mph....

[Buffalo444]

Im thinkin anyone who does custom tunes can help with this as long as they can get the pcm code or whatever it is off the donor... or maybe its the VIN? Wish I could be more help, but I'd try contacting them.

[SuperCrutyPS]

It isn't all tires - Something else going on too.

Tire size calculator - According to that link your speedo should only be about 4% off. 60mph should actually be 62.3.

If you're only seeing 60 at 75, it isn't all tires.

[97e350]

That's what I was thinking unless the donor was programed for very big tires and now these are small.

I was reading on another forum that on a 2000 E-350 the sensor in the rear end is for the abs and the speedo sensor is on the trans for the speedo. And there is a gear on there that can be changed. The previous owners age gone and I don't even think they know about. They were lying thru their Teeth.....

The van itself is a 1997 but it looks like the engine, trans, computer, wiring harness is from a 2002 and the gauge cluster says Diesel Fuel Only so that should be from it as well....

[97e350]

I've been searching and can't find a straight answer. Anyone???