The one thing you don't want to do when climbing a grade is to let the engine lug. Downshift and maintain the RPMs at an acceptable level and you will be able to climb grades all day.
That being said you need to make sure your temp guage is accurate. The guage on my truck showed a temperature that was 20 degrees higher than the actual temperature measured by a certified accurate aftermarket guage. So when I thought I was hitting 220 I was only at 200.
Also if equipped with a fan clutch make sure the fan clutch is engaging.
