i know on all of the cars I have worked on including my 90 trooper you have to use a gear puller to pull it off. The gear has such a tight fit that you have to use a puller to get it off. and to get it back on you usually can heat up the gear and pound it on with a hammer and a soft piece of material like wood or a brass rod so it doesn't damage the gear. If it is the timing gear you are talking about, I dont know how many miles your rig has but it is usually a good idea to replace the timing set while you have it all apart.