YJ/TJ/XJ/ZJ are all 5 on 4.5
CJ are 5 on 5.5
So how can you tell, here is a copy paste that I found:
Use a tape measure.
4 bolt: measure from outer edge of one bolt hole (or stud) to outer edge of opposite bolt hole (or stud). Same with 6, 8, or 10 bolt pattern.
5 or 7 (or 9) bolt pattern is trickier, so pay attention: Measure from outer edge of one bolt hole (or stud) to HALFWAY through the opposite bolt hole (or stud).