* Check the Vehicle's Data Plate: This sticker, usually located on the driver's side doorjamb, may list the axle ratio (often abbreviated as "Axle Ratio" or similar).
* Look at the Differential Tag: The differential itself (located in the rear axle) usually has a tag with the gear ratio stamped on it. You'll need to jack up the rear end and possibly remove a cover to see it.
* Check the Owner's Manual: Though less likely, the owner's manual *might* specify the axle ratio.
Without knowing the specific engine and transmission, it's impossible to give you a definitive answer. Common ratios for this era of van would likely range from 3.07 to 3.73, but this is just a guess. You must check your van's specifications directly as listed above.
