Is there a way to firm up shifting on automatica as well has hold the gears longer? I am thinking of changing to larger tires. I run 4.10 rearend with a 360. I waould like to run 36's but want to be sure it doesn't shift too early and bog down. Also would like have a firmer shift to extend tranny life. I have read posts that say when you change your speedo gear, it recalibrates the tranny shift points. Is this true also. Earlier posts about changing pressure in vacuum lines?