Mine has always been quite accurate. I routinely make a 600 mile trip, I calulate by hand, and it usually is within a few 10ths.

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Gordon

 

Mine is always 1 to 1.5 MPG higher than hand calculated.

 

I have had an issue with my 2011 f250 tranny slip from day one the CEL came on at 8k
had the new update done 2wks ago the CEL kept comming on they replaced the nox sensor no moore light. but after the relearning process the trany flares are still there now that it has on the right the gear you are in I can see that it skips 4th gear and goes to 5th from 3rd and that is when it slips dealer and ford can not tell me why

 

It actually is designed to skip gears depending on the load request, rpms, and other readings. Thats where the "learning" process comes in. You might not be completely through with the relearn.

 

I don't have any slip so to speak but mine always jumps from 5 to 3 or 6 to 3 or 2 when slowing down quickly in traffic. It's a smooth shift IMO.

 

It is on up shift and med exceleration it slips to were it hits 4000 rpms and the trany makes a loud squeek when it engages 2100 miles since upgrade