if you don't have it, get an owners manual, and see where you are as far as services go... I will say, as a shade tree mechanic... Don't fix it if it ain't broke... Don't waste your time and money on things that don't need to be touched AND if the service manual says it takes an hour, give yourself 4, and have an alt. mode of transportation just in case you can't get done what you need to.
1989 Cherokee Pioneer 2" lift 31x10.5r15 hercules all trac A/T
http://goo.gl/h3lf9 youtube channel.