so what i thought was a little problem (not down shifting) has gotten worse, 2nd gear is slipping bad and 3rd is not much better. so I'm going to have it rebuilt and i was wondering what mods i can have the rebuilder put in to make it stronger and last longer. I plow with the truck,and its a utility body loaded with tools, I don't do much towing. Its a 99 250 with 320+k miles on it