Jeep Grand / Cherokee - When were they permanent 4x4 ?

[OnlyMX5ives]

Hi I'm looking to buy a Jeep Grand / Cherokee.

I know the early models were only 2wd for the road, when did they change to permanent 4WD ?

I'm looking at getting a 4.0 or 4.7 just for a change and a bit of off roading is there anything in particular I should be aware of ?

I've tried looking on the Jeep forums but they get into such specifics its hard to find the basic info.

Thanks

[OnlyMX5ives]

Ah that would make sense - Dad has a 2.5 in stock which is 2wd.

I just assumed it was an age rather than engine size related.