What size is the rear axle?

Tell him to crawl under the vehicle and get the tag numbers off the rear differential cover. On the very rear of the differential cover there are two small metal tags under the bolts that hold the cover on that will give him all the information needed to identify his particular axle.

If he doesn't have the right tools there to do it, ie magnetic base dial indicator, torque wrench and so on, I do NOT recomend him trying to change the differential. If the gears are not set up correctly then you will be doing this all over again much sooner than you want. Possibly even within a thousand miles or less. I would definately find an axle from a junk-yard or a jeeper that has upgraded his axle. What you need to look for when trying to find an axle is to make sure it has the correct gear ratio. If he doesn't know this it is easy to figure out. Roll the Jeep forward one rotation of the tire. Count how many times the driveshaft rotates in that one rotation. Factory gear ratios are 3.07, 3.73, 4.10, and 4.56, so if the driveshaft rotated a little over 3 times then he has 3.07 gears. If it rotated a little under 4 then they are 3.73 gears, and so on. Also the 3.07 gears were only available in a 6 cylinder with a manual transmisson, and the 4.56 were only available with the 4 cylinder. Any rear axle out of a TJ from 97 to current will work, and even the wrong gear ratio will work temporarily. But if the ratio's don't match then you must remove the front driveshaft. Failure to do so will result in serious damage to the transfer case. Please contact me if you need further assistance.

if it is a Rubicon its a dana 44

if its a wrangler its a dana 35

if your buying new gears for a d35 you will need a new carrier for gears bigger than 4.10, the ring gear is too big.

Get a Detroit locker for the rear and ARB locker for the front.

*** never mind i read your additional comments. if it is a Jeep Wrangler it has a Dana 35 unless it is a rubicon eddition it will be a Dana 44 ***

if you are buying parts for the truck you are going to have to pay someone to install the parts. Gears are a very difficult item to remove and replace without the proper tools "and experience". This will run about $450-$600

the other option is find a totaled jeep and just buy the complete axel. This might be cheeper and easier in the long run!!!

Check for a tag on the axle cover bolts, this should display the information you need on what type of axle. Not for sure, but if you call a dodge dealer with the VIN they can tell you that information also. Good luck.

It's a Dana 35.

Every one that I have seen has the 7 1/4.

Your in luck I am a owner of a 98 jeep wrangler.

- stock gears are 410

-I changed my to 373 to get better gas milage

If for some crazy reason he can't get to the tags, this web page has pictures and measurements of differentials. If you can get the page to him, he can take a peek and see what he's got.

http://www.quadratec.com/jeep_knowledgebase/articl...

By Size, do u mean, Axle Ratio, or Final-Drive ratio, to be more precise?? If so, you can get it in the user's manual, if u got one. OR try searching for it in any automobile sites... You should get it with least hassles.