My SCT Xcalibrator is being updated for the gears and a 91 octane tune is being added, so I have the factory tune in at the moment. The speedo is off maybe 5%, but I can compensate.

The 3.73s are a great combo with the ratios of my auto. Should have been in there from the start. I find a lot better low speed response in intermediate gears like 2nd and 3rd. With the 3.31s it used to lug a bit. First was never a problem. That was and still is a stump puller. The boost in getting up to the power band is noticeable.

I do recommend using the FRPP gears, the install kit, and Motorcraft lubes, and a good experienced mechanic if you're not up to it yourself (like me). My mechanic has been servicing and modifying my Mustangs for quite a while, and he did a great job again. So, I'm not at all concerned about paying him a little over $400 for the install. It was well worth it. No grinds, no clunks, no noise at all. Just like OEM.

 

I'm such a big believer in gearing up musclecars, that my '07 GT automatic had 4.10's installed when the car was only 2 weeks old. Welcome to the steep gears club!

 

Congrats....gears should be one of the first mods along with a CAI/tune.

 

Its a nice Mod. 1st in my GT & 3.73s with the TR3650 could be a little taller as could 5th. But the other gears seem about right. If I get any Tranny work done in the future, I think I will see what it would take to exchange the 0.68 5th with the 0.63 gear which comes in some version of that transmission.

 

Funny, when I first got the GT new in '05 I did a bunch of mods - CAI, Tune, Alum Driveshaft, UD Pulleys, FRPP Axle backs. Don't know why I didn't do gears then. But better late then never. I didn't do much in 2007-2009 other than enjoy the heck out of a great car. Now, I'll enjoy it more.

 

Love the 3.73's, nothing like jumping out in front from the light!

 

still debating if i should get the 3.73's or not. i have an auto and a single turbo. i hear different advice on which gear is better for my set-up.

i have heard that the 3.31s are better because it will give the turbo more time to spool up. i also heard that the 3.73s are better because it will create more load on the engine and help it spool sooner.

i am leaving it as is until i figure out for sure. until then, i have a whole bunch of other stuff i can mod.

 

If I had your set up, I would leave them alone or maybe do 3.55s if the cost wasn't much of a factor for you.

 

yeah, i wish my car came 3.55's stock. i think those would be the perfect compromise for the turbo. for the dollar, i don't think i would notice THAT MUCH of a difference going from a 3.31 to a 3.55. so if that is the case, i would just leave them alone.

 

You did the right thing by having these installed by an expert. Gears installation isn't for the first time mechanic. There's allot to consider and if you don't have the knowledge and the proper tools you're in for some frustration and noisy gear whine. In two weeks I'll have my 3.73's + a TruTrac + New axle shafts too.

 

I had gears put in my '96 by somebody who was in a hurry. For a long time I had a clunk on deceleration. Finally, I had Jeff rework the whole rear end and put in an Eaton differential. It's been running fine for over ten years. My son-in-law has the car now, and every once in a while I demand my right to take it out for a spin once a year

 

Well I'm glad in the end it worked out for you. It's very tempting to take on something that maybe way over you're head. I recently saw an Extreme 4X4 show on how to install & set your gears. He made it look easy but in reality it takes a lot of time and knowledge to get it right. I'll try to post that segment in your thread. It's very interesting to watch but not do yourself.

Here you go...Now I know this isn't a Mustang GT rear end but you get an idea what's involved...

(Click Da Pict to play)