I got two I’d tags on my differential..
one is 3.5 the other 1080..

does anyone know what these mean..?

Thanks!

It might help to know what axle you have. In the Sticky Threads section right above this one is a thread titled thread " AXLE INFO: " and it has good information in it.

Some info on your Xj would help as well. What transmission? That "3.5" is probably actually 3.55 gear ratio if you have an automatic. Look below my post here at my signature. That info in your signature helps a lot when trying to figure out issues on peoples vehicles. Year, Engine, Trans, T-case, axles stuff like that.