I bought my 2006 Ram 2500 MegaCab Oct 2011. It had 315 tires that had <4k miles on them. Now buying new tires. Deciding between 285 or 315. I keep hearing about regearing. How do I know how my truck is currently geared? I would LIKE to assume it was geared appropriately for the 315s. However, I had to have transmission redone January 2012. So, I would really like to know what my gearing is. Can you help please???