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Torsen Diff without using friction modifier questions

My local Ford dealer recently replaced the pinion seal and both rear axle seals under warranty. At that time, they neglected to add the friction modifier to the diff fluid. My questions are these:
1) What should the diff operation typically feel like without the friction modifier?
2) How long can the car be driven on the street without the modifier before damage is done to the differential?
Yup, friction modifier is only required for clutch type LSDs. If you have the torsen/recaro package, you don't need it

Although, some people add it in, saying it reduces gear noise. I've never felt a difference. Then again, my gears have always whined.
The Boss 302 Supplement to the owner's manual that came with my car lists the friction modifier as one of the part numbers for the fluid in the diff. What's up with that?
I noticed the same thing in the GT350 Owner's Supplement, that it calls for the friction modifier. The Torsen differential is standard equipment on the GT350. That said I know it was said many times the Torsen doesn't require the friction modifier, even on their website. I believe it's added for noise reduction to alleviate customer concerns.

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