You can add shims to make a trac-lok so tight it won't ever disengage. What I think you are describing is the effect of torque transfer.
The clutches attempt to route power equally to both wheels. However, if you have one wheel on a surface with good traction and the other wheel in the air, if you give it enough power the clucthes will be overcome and the airborne wheel will spin. Applying some brake slows it down enough to let the clutches hook up again.
"Trac-Lok" is a Dana trade name -- sort of, I think. Reider Racing sells Dana-Spicer Trac-Loks, but they also sell something called a PG Trac-Lok, which I believe is a Precision Gear knock-off of the Dana unit, for diffs Dana doesn't service. I've never seen a PG Trac-LOk and don't know if it operates the same as a Dana.
Note that the FSM allows for a wide range of acceptable torque bias. 30 ft-lbs to break loose a LSD diff is rather anemic, IMHO. In the old days of autocrossing AMC stuff we considered a LSD to be worn out if it torqued less than 50 ft-lbs.