Speedo gears and bigger tires

I am going to be messing w/ the speedo soon (adding a R. angle adap) and a new cable and figured while I am at it I could change the gearing to match (closely) the 33s. I have 4.88 gears in a factory stock V6 drivetrain. The chart in tech says it has a 22T 448495 drive gear w/ a 447331 driven gear. My effective ratio is not as high as a 3.73 (16T w/ a different driven gear) but it's probably higher than a 4.27. I'm having trouble wrapping my mind around it and hope you all can help me out. Would switching out the drive gear alone (to say the 18T 448493) do what I need? or Would I need to swap out both to a different gear set?

Driven Gear Used With Driven Gear
Teeth JEEP P/N SW number T/Case JEEP P/N SW number
18 910087 448493 D18 910086 447331
20 910088 448494 D18 910086 447331
22 910089 448495 D18 910086 447331

 

you need to switch both as the teeth are spaced different.

JP had a good article couple months ago about correcting speedometers.

 

From 18 to 22 teeth drive gears all use the same driven gear if I read it correctly (447331).