Yes you should just because your speedo will be off a lot more than you think! Plus the fact that you will have a hard time figuring out how many miles you are puttin on.
in my 2011 i had 3.73 and 35's for a long time (its equivilent to what you have with the 3.21's) and by long time it was 3 months. that was the longest 3 months i have ever driven in my jeep. it was soooo slow it was crazy. that being said if i had to suffer like that again in the future i would because at the end of the day i got my gears upgraded and it is now amazing!
