LSD for Ecoboost mustangs

Every Mustang since 2011 model year comes with a limited slip differential.

I believe that the stock gear ratio is 3.15. With the automatic I wouldn't go more than 3.55 - the automatic gear ratios are such that any higher makes 1st pretty much useless =

Thanks for the reply brother. When you say useless do you mean that it'll reach redline pretty much instantly? Also, do the axles need to be removed and shims used to check gear lash?

Correct, you will be through first gear so quick that it is like it isn't there.

If you change the ring and pinion then yes, you have to remove axles, adjust the shims, and check gear lash.

But I'm not sure it is easy to swap on the S550. I think that you are supposed to change the entire hosing i.e. remove the current and then insert the new one with the gear set you want and put the axles back in place; different gears don't go into the same size "pumpkin" so it is fully swapped out. Very different from the S197.

I would go with a 3:55 rear gear. Only performance package cars came with this gearset. I believe that standard cars came with a 3:15, as previously mentioned. Probably the best way to accomplish this change is to buy a complete rear differential assembly. These can be had through any number of suppliers, such as American Muscle and Ford Performance. That way, you won't have to mess with shimming, pinion preload, ring gear backlash and tooth pattern. It's complicated. The diff. swap would be fairly simple. Well worth the money. I have a 2015 performance package car and really like the rear diff.

i have thought about going to the 3.73 gears but the stock Torsen 3.55 in mine is really nice

The price difference between the rear diff assy and the gear set is quite a gap but I'm sure not worth the hassle of just getting the gear set. Drop in and play is more my speed and sounds more reliable to me. Definitely will be marinating on this for the weekend. This was one of the things that I was thinking about doing as well as installing koni adjustable a to go with my springs. The stock struts and shocks just aren't cutting it. You guys are the best. I'll keep you posted on what I decide to do. Thank you so much and all you guys have a blessed and wonderful holiday weekend

I think the 3.55 is ideal.
My first S550 was a Performance Pack Ecoboost auto with 3.55.