Hey, i put 20 inch rims on my 94 ranger that originally had 15s, my speedometer is reading five miles slower than what I'm actually going, what type of speedometer gear do i need??? I have the yellow one as of this moment if it helps!!

 

Rims size doesn't matter and won't help you figure out what new gear to use.

So can't help you

Also Manual or Automatic trans matters as well
Since you have a Yellow gear and 2WD then you should have a manual trans

BUT(big but).............

You can help yourself
You need the tires Diameter to calculate gear change, 20" rim could have low profile tires so..............??
That's why rim size doesn't help, you need full diameter of the tire to see how far it rolls in one revolution, so you can see how many revolutions are in 1 mile, with that you can calculate MPH by drive line/axle rotation.

Read here: Ford Ranger/BroncoII speedometer gear change/calibration

You can use "how far off is the speedometer now" to figure out which gear to use