2007 International 4400 speedometer accuracy

I haven't came across this issue yet. Trucks got a 466 and an Allison transmission.

Got a speedometer that is reading off a bit. Speedometer reads 15mph-gps 20mph. Then gradually the difference grows. Speedo 30-gps 45. Speedo 45-gps 65ish. Does not having any shifting issues.

Changing the tire revs, trans tail shaft teeth, or gear ratios in ecm parameters does not change the speedometer reading. Also swapped tail shaft speed sensor and speedometer cluster with it's sister truck and it had no affect on the issue. Voltage readings at the pigtail match the other truck. Roughly 4v on one pin and 1v on the other. I did not see any changeable parameter setting in the tcm for speedometer calibrations.

Wondering if anyone has come across this before or has some input. leaning towards swapping out the ecm just to try it out

 

ECM reads the same as the cluster. The speed parameters also match up to the other truck's settings.
But, yeah I've never came across one that doesn't like this.

 

No, it has a the electronic instrument cluster style.

 

I did end up try that out. i maxed out tire revs, changed tail shaft teeth, and gear ratio. Performed BCM and ECM updates. But had no changes.

It got dropped off at the dealer with the sister truck that had to have the ecm password protection removed. I"ll update if they figured it out.