4l60e will not shift into 4th gear

[rjenkins]

We have a 04 5.3 with 4l60e 2wd that will not shift into 4th gear, we have updated the data for the vss and the differential gear ratio. The speedo reads vehicle speed within one mph of gps speed but the computer never commands 4th gear. OS is 12587603. Any help is appreciated.

[B52Bombardier1]

Any codes for DTC P1860? How many miles on the trans? Ever been rebuilt? Can you manually shift it into 4th gear? I'd be interested to see what a good scanner would show for the commanded gear.

Rick