Is it okay to put posi-trac friction additive into a non-posi-trac differential?

look on the rear end of the car and look where the bolts are on the differential then look for the tag that is about 2 1/2 inch's long by 1/2 wide record the numbers and get the vin off the windshield on the drivers side and call your local ford dealer parts store or any transmission shop and they can tell you what it is. If I remember correctly the additive will damage the non posi-trac Diff. will cause friction wear and failure of the pinion bearing and seals and possibly te wheel seals. call to be sure I could be remembering incorrectly.