i pritty sure that the 4-tec has ball diff's. if that is the case all you need to do is take out the diff, after taking out the diff there should be 2 sides of the diff (one for the left and right axle). there should be a screw inside one of the outdrives. after you locate that tighten the screw ONLY HAND TIGHT! dont crank on it because i think we all here have had experiences were we tried to righten so mich we broke the screw. then after that your all set. you can makes these adjustments accordingly, if you want it to slip more or less, its up to you.

the other way you mentioned is CA glue, with that i wouldn't advise you to do that unless you have a spider diff.

another way you can lock it is like this, http://www.drccentral.com/forum/viewtopic.php?t=10175 .

hope that help!