Ford U7153 incorrect speedo reading

[Casper]

2002 Ford F150 5.4L VIN. L

Diablo Sport Predator U7153 revision 8R02

Just recently installed bigger tires and new gears. Tires are a 285/70/17. Set the tire revs at 616.

Set new gear ratio to 4.09. Speedometer reading is off. When vehicle speedometer is reading 60 mph, my GPS is reading 53 mph.

I am the neighborhood of 7 to 8 mph off depending on the level of speed of travel. The faster, the more this amount is off.

The program I have in it right now is the Diablo Sport Performance Tune. I have not tried the factory HP Tune to try and fix the problem.

I have read through this forum and found others have had this same issue with the 7153 programmer, what is the fix for this problem? I realize my revision in my programmer is the older update. If I would update to the newest revision (9R04), will this fix the speedometer problem? Does this latest revision keep the same benefits of adjustability as the revision 8R02? For example, adjusting for injector size, global spark timing, etc.

[mikel]

I would say updating is the best thing to do here.
If it does not fix it, at least it will make it easier to fix in a custom tune

[Casper]

Does this latest revision( 9r04) keep the same benefits of parameter adjustability as the revision 8R02? For example, adjusting for injector size, global spark timing, rev limiter, transmission shift points, OBD2 parameters, etc. Or will I lose some of the adjustments, or gain new ones and what ones?


Thanks

[mikel]

you will lose OBDII params.

[Casper]

Thanks Mike For the quick response. As soon as I get the cable and power adapter. I will down load the new revision and see what happens.


Thanks

[Casper]

Hey Mike:

Updated the programmer. The update did help the speed come in closer. Now when I am going 60 mph on the speedometer, the GPS is reading 57 mph. So could I tweak the tire revs to get the speedo closer to the GPS speed? Right now the tire revs are set at 617 (tire size 285/70/17). I think I need to subtract from the 617 number to bring the speedo closer. What is your opinion?

Thanks!

[mikel]

Yes, a little fine tuning is all you need now

[Casper]

Hi mike, Thanks again for the infro. Should I subtract from the tire revs, or add to? By how much? With the speedo reading 3 mph faster than the gps. I think you subtract from the tire revs. Also, How may tire revs equals 1 mph?