Have a 544G on site, when cold it wont shift past 2nd into 3/4 until warm, is this an issue, or a setting that can be changed.
When cold, does the speedometer work when the transmission is in 1st or 2nd and the no 3-4 gear issue is occurring ? If the speedometer is not working this indicates an issue with the transmission output shaft speed sensor and or wiring.
Losses in axles, differential ans transmission might be too high when cold to reach upshift rpm. Thinner oil might improve or park in garage.