3.73 rear gears on a v6?

V6junkie said:

Never done gears before and I have an auto and I'm sure this has been asked but what all would I need if I wanted to upgrade to 3.73s..... different differential?.... just the gears?..... is their a full kit? I'm interested in doing this just want to make a plan to go forward with it

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I asked the same thing. What I know is you need the ring and pinion, but I haven't seen an install kit like the old solid axles to bring down install costs from a shop. You can pair the ring and pinion with a T-LOC to upgrade the limited slip we currently run (expensive). All you really need is the ring and pinion from what I can tell. What I don't know is if install costs is more cause unlike the old solid axel I do not believe a gear swap can be done while it's still mounted to the car. They have to actually pull out the whole pumpkin. Seems it would make this a super pricey upgrade. Old gear swaps from a good shop, not a dealership, would run 300-400 with you providing parts. Total investment in the range of 650-800.

Been lurking here for a few days reading up on the tech info, good stuff!

I know this is kind of an older thread, but I looked into this for my own car so I felt I could contribute something to the conversation :-)

What I learned in my research is there is only 2 rear gears available from the factory on the '15-newer v6; stock is 3.15:1, optional is 3.55:1. Also, to confirm what was mentioned in a previous post, all V6 Mustangs now come with limited slip differentials as standard equipment, however, according to the Ford Racing catalog if you have 3.15 or lower numerical gears you need to change the trac-lok to install 3.31 or higher numerical gears.

My opinion; when you add up the cost of new gears, a new trac-lok differential, plus parts and labor to set up the gears, you're probably better off sourcing a used pumpkin with the gears you want and just swap it out for your stock pumpkin, or get a complete IRS to make the swap even easier, there's always used rears for sale on eBay, if you don't see one with the gears you want just wait, it'll pop up.

Also, the pinion flange is different between auto trans cars and manual trans cars, so if the pumpkin you get doesn't match your car you need to swap that flange to hook up the driveshaft.

One last thing, afaik the only factory installed 3.73 gears came in the performance pack option which also includes the torsen lsd, a much better lsd design than the trak-loc! That's a good reason in itself to swap pumpkins instead of paying to install new gears ;-)