On my 88 XJ the owner's manual says I can go from 2 hi to 4 hi at any legal speed, the US speed limit was 55 mph when they wrote the manual. To go from 4 hi to 4 lo I need to be moving forward at 2-3 mph and then pull it into 4 hi. I found the easiest way to get out of 4 hi is to stop the vehicle, put the transmission Neutra and then shift the transfercase to 4 hi or 4 lo. I go into 4 lo about once a year so I always check the book to make sure. You do need an owner's manual
With web posted information is may or may not be accurate, in your case it may be the US version but the Canadian version is different in the area you are interest in. Also I have adopted the attitude IF I use the information THEN I need to pay the author for their effort. To me you can go to the library and look it up in reference copy, but to have a digital copy which you got for free is just wrong. Now the end of my protection of copyright speach -
I highly recommend you buy all the manuals for your XJ from Jeep, they will more than pay for themselves with the jobs you can do with their information.
A place I'd turst the informtion is
www.alldatadiy.com they offer a 1 year subscription for one vehicle for US$25. I recommend manuals plus alldata to maintain your XJ, not sure if alldata makes an allowance for Canadian models. You have access to all the Technical Service bullitens for the vehicle. I read through the list and found a few minor things i could fix on my 88 XJ. Also Alldata gives you procedures, book labor hours, OEM part numbers & cost.
If you want to save some money go with Alldata first then buy the manuals. You should get your codes and reset procedures from them.