I have an 03 2500hd with a 6.0/4l80e. The trans has a deep pml pan, trans-go hd2 kit and has been serviced regularly. I have a strange issue when cold, seems to only be when the temps outside get to 40 degrees and colder. When i go down my street it shifts to 2nd fine. When i pull out it seems to shift into a higher gear like 3rd. if i stand on the gas it down shifts and is totally fine. Also when it gets some heat in it the shiftings totally fine. I have no issues of slipping or sloppy shifts, it shifts pretty nice. First is firm and the rest are a little softer but still clean shifts. This issue has been there for about 5 years, its nothing new but i would like to fix it.

 

Hard to tell but I'm guessing you're asking why the 1-2 shift is more firm but still clean? Do you happen to have a corvette servo in? Or maybe your tune has shift pressure higher for the 1-2 shift?

 

He has a 4l80e not a 4l60e.