These diesel tractors don't make much power until they are in their proper operating powerband, usually between 1800 and 2400 rpm. If you're in the high range gears you won't be able to pull hills in anything but 1st or 2nd gear and then only if you start out at full rpm. For actually pulling o hills, like plowing, mowing, etc, you'll need to be in low range, and then you pick the gear that gives you the forward speed you want when the engine is in the powerband.
Your terminology/description is a bit confusing to me,. though. Are you saying that when the engine is cold that it will pull hills in high range gears 2, 3, or 4? Or are you saying that it won't start from a dead stop on a hill when it is in high range? Or something else?
I have no idea what you are referring to when you say "double low". These tractors have a four speed gearbox with two ranges high and low. So you have 1st low, 2nd low, 35d low, 4th low and then 1st high, 2nd high, 3rd high and finally 4th high. That is, unless you have creeper gear - I dont have that on my tractor and don't know exactly how it functions except that it is a really low gear setup of some sort.
Generally speaking, your engine should have more or less the same power available whether it is cold or up to operating temp. It will be slightly better at temp than it is cold, but there shouldn't be a huge difference. It is better for the engine to operate at full temperature so most users let the things warm up for ten or fifteen minutes before putting a load on them.
Can you be more specific about the problem you're experiencing, using the gear terms I've outlined above? That will make it easier to help diagnose your issue.
