there is no way of telling what's in an 86 MJ's axles without looking. Everytime we think we've figured something out, a truck pops up that breaks the mold. Jack up one rear tire, put the trans in neutral, and spin the tire around exactly twice. the number of times the driveshaft rotates is your gear ratio. If by chance there is a posi in the rear, then jack up both tires and spin them only once.