Question: what is the difference between d4 and d3?
Answer: D4 is where u should be driving normally "in town ,freeway, ect" now D3 is very similar however D3 should only be used when driving down hill. It will downshift 1,2, or 3 gears depending on speed, to slow vehicle down "downshifting " this will save ur breaks from alot of wear & tear!