What backspacing do I need for 31X10.5R15 wheels?

[JMT]

Also, how do I find out what kind of axle I have for the rear? I have a 1998 TJ 4.0 Sport with a 3.73 ratio. I am unsure of what I have. Do I have a limited-slip differential? I bought this jeep as it is and I don't know anything about it. What I do know is that the previous owner beat this Jeep and I had to get a full rear differential rebuild from my mechanic.

From what I was told, my teeth in the differential were broken, I think. I know he said that there were metal shavings in the differential. I think my mechanic said the control arms were ripped off, so he had to rebuild that as well. As well as the shocks not being bolted tight at all. According to my mechanic, he had to retighten every bolt.

The person who I bought my Jeep from said that my Jeep originally came from Vermont, that's all I know about the previous history about my Jeep.

Oh, and my mechanic said that the previous owner or someone put a different differential plate on my rear axle so to find the ratio of my axle he had to tape a tire and the driveshaft and spin it and count the rotations I guess.

Post a pic of the axle

 

[JEEPCJTJ]

Your wheel studs should be long enough.

Yes they should be, but you never know what somebody may have done.

Your Jeep is not a fragile toy. Regardless of its past, unless it’s a rust bucket, it should be fine to off-road.

This is definitely true!

 

[Goatman]

Look for that "3peak" rating system for a good tire to deal with the snow if you are talking about snow on the road. It is a government rating given only to tires that do well in on road winter conditions.
Mud tires are built the opposite of what a good on road tire should be for good traction on road for snow and icy trcation.
You want smaller lugs with smaller spaces between them with a lot of siping in the lugs. A good all terrain or a dedicated snow tire is what you need.
The Cooper AT3 4s LT (the 4s means 4 season) IS a 3peak rated tire. There are others. But I've had fantastic experiences with the Cooper in sow and ice here in NY.
You seem to be saying two different things. 1) how is this mud tire? How about this mud tire...) 2) I need a snow tire. Has to be a snow tire.
Those are two different directions for a tire to be. Any tire with large voids with no siping in the blocks will be crap for snow and ice driving conditions.