rearend woes???

You have an 8.8" rear. DONT GET FACTORY GEARS REINSTALLED!!!!

If you're going to need to replace the gears, have them replaced with 4.10's! All gears cost the same amount, dont waste your money and replace with factory 3.27's.

Could just be the Tack-Lok binding/grinding/chattering at low speed. At almost 120K it's probably time for a rebuild anyway. I wouldn't think anything's wrong with the actual gears though.

Yeah, all GTs & Cobras have a 8.8" but V6s have a 7.5" though, maybe that's why they asked - those guys have to keep up with a lot of different models and can't necessarily keep track of all that trivia in their heads.

As stated dont get factory 3.27s installed if your going to rebuild your rear end.

+1 on the trac-lok probably needing to be rebuilt

Rebuilding the Trac-Lok really shouldn't be a big deal for a dealer, but ask around, there's gotta be a reputable transmission/driveline shop nearby that can do it, and probably for less than the dealer. They can verify for you that it's the Trac-Lok and not the gears too so you don't pay for repairs you don't need.

If you do a burnout, do both wheels still spin or just one? If just one, it's definitely worn out.

It's possible that it's still functional. If you changed the fluid and didn't add the recommended friction modifier, that could be why it's making more noise when turning at low speed. How long has it been doing it?

Well, that sounds unrelated to the rearend issues. There could be many sources of those smells...

Coolant could be coming from cracked intake (very common issue on 96-01 Mustangs and other 4.6l), over-filled overflow tank dumping excess coolant, overheating causing coolant to boil over, pin hole in radiator, leaking hose, leaking intake manifold gasket or water pump gasket, bad water pump...

Is it loosing a noticeable amount of coolant? Can you tell where it's going? The first places to look for coolant is in the block valley, spark plug holes and on the front of the block and oil pan. If it's a small leak, it can be hard to find sometimes though - a few drops of burned off coolant can really stink things up.

Oil smell is under the hood and not in the exhaust, right? Any visible smoke under the hood when you smell the oil? If so, see if you can trace it to the source. The PCV system is the first place I'd look - when's the last time the valve was replaced? Make sure the hoses are all in good shape - no rotting or cracking. While running, look for oil dripping from a valve cover gasket.