2007 nissan frontier 4 wheel drive--there is a vibration that happens at 1250 rpms. What would cause this? With rpms higher or lower minimal vibration.

What is your question?

happens at slight upgrade on road and at 40 mph

What makes this problem better or worse?

Slight upgrade in the road around 40 mph

How long has your 2007 Nissan Frontier had this problem?

month