Originally Posted by tev9999
1. Set cruise at 74 mph on a flat highway. Verify about 2000 RPM.
2. Press Cancel to disengage cruise.
3. Coast until you reach 65 mph or so - as if you just came up on a slow moving truck passing another. Don't touch the gas.
4. Press Resume. The truck will downshift to pick up speed faster and settle back in at 74, but won't upshift to 8th again when it gets there. RPM about 2600.
5. Press Gear+ to drop to upshift and drop to 2000 RPM.
Note it did lock in 7th at least once when I was not using cruise but had slowed down, then sped up again.
This only seemed to happen in the 70-75 mph zone. When I was on highways with 55 or 60 mph limits it would cruise along around 1600 RPM, I'm assuming in 8th.
Just tried this on a 2014 truck (5.7L, 8HP70, 3.92 axle) and could not duplicate your problem (it would shift back to 8th when it reached about 72 mph). Not sure if there are calibration differences between 2013 and 2014. I am trying to get my hands on a 2013 truck to repeat the same test. I'll let you know if I find one...