I just bought a 08 jk and have been looking it over. I lifted rear tires to do the tire spin test to see what gears it has and if LSD. I have read that the tires spin in opposite directions if open diff. When i spun the tire the other tire didnt move for abit, then it started to move opposite. Spun opposite tire and the other spun backward. Then at some point of spinning I noticed the opposite spun the same way. This confused me abit.
Next test was to determine gear ratio. I spun one tire 10 revs and counted 10.5 spins of the driveshaft which would end up being a 2.10 ratio. I dont think jeep made this ratio. I test drove it for a couple miles and did not notice any issues. Is this normal?

 

Sounds like an open diff to me. Cannot determine the ratio like yyou are doing. Take the cover off, change the oil anyway and read the number of tooth count on the ring gear. Most likely 3.21 or 3.73.

 

Rotate the the tire one revolution, use a mark on the tire and drive shaft - chalk, paint pen, etc… count the turns of the drive shaft if you’re not opening it up.

 

I am planning to change the diff oil soon. I will pull the cover and check the gears for sure. Was just wondering if those movements were normal of the open diff.

 

If you block the driveshaft P or in gear then raise both wheels if an open diff they will turn opposite. What you describe is normal for open diff. Even lockers do the same when unlocked.

 

Thanks sixty! I appreciate the response and good news.