tq! and may i know rather than the ring and pinion ratio have to be the same for both Front and Rear Axle....then how about the Axle model, does it matter,like Dana 35 etc! also May i know is ZJ using Dana axle or other Model/brands? Tq again!  CN  

It dosnt matter what axle you use as long as the R&P are the same. If it was just used in the mud it wouldnt matter so much. But on the asphalt it would tear things up pretty fast with the front and rear wheels wanting to go different speeds.  

may i know rather than driving on the asphalt it would tear things up pretty fast, will it Damage the Gear Box or any Gear if i change both the Front and rear the same ratio to 3.73 ratio? but i just afraid that whether the new set R&P doesn't feed in to my front axle, will it happen so..? CN  

Hello I have a 1998 jeep Wrangler w 4" I had the same problem, I found my shifter fork in my 231 transfer case was bent I replaced it and it works great,I beleave it bent beacause I didnt have the braket to relocate my shifter linkage so when I was in 4wd it was never all the way in gaged.

Good luck  

According to the NV231 Service Manual if the transfer case is noisy while in, or jumps out of 4L mode it could be because of the following.

Transfer case is not completely engaged in 4L position.

Transfer case shift linkage out of adjustment.

Transfer case shift linkage loose or binding.

Range fork damaged, inserts worn, or fork is binding on the shift rail.

Low range gear worn or damaged.  

cnchua, on most jeep axles I have seen, there should be a couple tags that are held on by the diff. cover bolts that have info. on them like oil info and gear ratio.  If they are still there, that is the easiest way to tell.  If not, then jack up the rear, put your rig in neutral, and turn the pinion.  Make a reference mark on the tire and count how many times it takes to make the tire go 1 revolution.  I would think you have a Dana 30 in front and 35 in rear.  They make 3.73's for both, and change both at the same time.  The only thing is that you'll be running a slightly higher RPM and your speedo will read higher than your actual speed.