Ideal gearing for a street car?
 

I’m in the process of hunting down my transmission and rear end, but I’m not sure what gearing to get. Which year Mustangs should I look at and which final drive ration should I be looking for?

And what ratio do you guys recommend for the rear end as well? Ill be going with the 7.5”

3:27-3:55's

With my 2,000+ mile journey 4 years ago, my Mariner blue 5.0L car, with 3:27 rear gears, averaged 25-29mpg on the highway at various speeds

https://www.v8miata.net/drives-road-...p-v8-1-a-1449/


Plenty of power to push the car with the stock 5.0L and 3:27 gear set, as the car weighs 1,600lbs less than the Mustang the drivetrain originally powered.

There's no such thing as a "perfect" gear. It all depends on what you plan to do, and what you want out of the car. If you want a gentle highway cruiser that gets good mileage, use 2.75-3.00. If you want a fun car that accelerates like a rocket ship, pick 3.73-4.10. A good middle ground is 3.27-3.55. Personally, 3.55 is my favorite with a 5 speed, 3.73 with a 6 speed.

Of course, if it's a high compression motor with a radical cam, stay with the higher number gears, like 3.27 and higher.

Back when I had a ‘94 Mustang GT I remember I had 2.73s in it, and then I went to 3.73s and loved them. I know the weight is different, but the engine RPMS at highway speeds were fine. Ill use it mostly for around town anyway.

Another thing that changes the 'effective' final drive ratio is tire size. You should take into consideration that the Miata runs a smaller tire.

And remember the overdrive ratio in the transmission used. The aftermarket T5z standard overdrive ratio is .62, compared to the regular Mustang's .67. My Miata with a bone-stock never-apart SN95 5.0 with the T5z, 3.27 rear end, and 225-50-15 tires (yeah, a little taller than the 225-45's...) is turning just slightly over 2000 rpms at 70 mph, will idle through the neighborhood at 35 mph in 5th gear, and on long road trips in summer with ac on gets 24-26 mpg; my most recent tally of 5,000 miles, with 2000 being interstates, and the rest being short local drives was 22.3.

I don't race; mine has been on the road for almost 8 years and about 22k miles of pleasure driving. It's a ton of fun, and does just what I built it for. Depending on your purpose, that will affect your choices, and as they say, YMMV. No matter how it's configured, it will be fun.

TM

Something you might want to take a look at that most people don't consider is first gear.
Find one of the online calculators that lets you input the ratio of each gear along with the rear end ratio and tire size and redline.

If the redline speed in first gear is low (as drag racers prefer), during normal street driving you will probably take off in second gear which effectively makes your 5 speed into a 4 speed when you do not want that hard launch.

Only personal experience I had with that was a friend who had a first generation Camaro with a 4 speed and 4.11 gears.
First was useless for normal street driving but he could launch really hard on the track.

So very true! I am running a T5Z with 3.27 rear gearing. It is almost a perfect combination for me. Remember to calculate in what your ideal cruise MPH is to what the ideal RPM "sweet spot" is of your cam shaft, or you will not be happy.

It seems the Z is the way to go with 3.27s in the rear (what Martin recommends in his manual). I will be running 3.27s with a standard 5.0 box (had one laying around from a prior project car). I don't think it will be the ideal setup, due to short first, but willing to give it a try based on already having it.

Let me know how the standard fox T5 works out. I not see many T5zs around for sale. So I was thinking Id probably end up wth a standard T5.

Hoping to be on the road this spring. Check my build thread for updates. I had the T5 laying around as I put a Z in my old fox. My biggest worry is 1st, as I am sure this thing will spin the crap out of the tires, first will probably be worthless. Not too worried about the 5th revs. We'll see.

A lot of people make a big deal out of first gear. But if you take a look at the spread sheet, you'll find that unless you're making a big jump - 2.75 to 3.73 - there really isn't much of a difference. I'v run 4.10, 3.55, and 3.27, and I'v never found first gear to be worthless. I think people get that impression because as you use lower gears (higher numerically) the car gets quicker, and you'll need to shift quicker time wise. But the rpm difference is so small that it's really not worth talking about.

Do the math.

Hi,

To answer your question quickly, I would say that 3.27 is the best gearing for general street use with a T5z 0.63 overdrive.

I am assuming that your engine will have an effective rpm limit of 6K and will be making good torque at 2000 rpm. This will put you around 2100-2200 rpm at 70mph. This is factory level gearing and it is relaxing for longer trips, its a nice place to be. It can be tiring being in a small noisy car with a throbbing v8 that wants to do 3000 rpm at 70mph for a long trip.

These cars don't need very short gearing (i.e. 3.7 and higher) as they are light. The torque of the V8 does the work for you :)

For general use 3.27 is about right...you can use a multitude of diff ratio/speed/rpm/tyre calculators on the web to get the right mix of rpm and speed for your tyre and wheel combo, to get a feel for what differences there are between tyres, ratios and rpm :)

I was thinking more about the transmission gearing, as the standard T5 has a shorter first than the z box. I agree, 3.27 it a great all around rear gear for this setup, just waiting to see about my transmission choice as it may not be optimal, but what I had to use.

From the looks of the used and abused T5's that I have seen in the past, you might come out cheaper by purchasing a brand new one.

I concur, old stuff = more hassles, removing and rebuilding later...do it once and well :)

Buy used, send it to these guys:

Hanlon Motorsports


They have been doing my road race transmissions for 15+ years

I rebuilt mine myself. Not hard to do. There is a guy that sells a video that is very informative (he is a Ford tech).

I have rebuilt hundreds of T-5's. The rebuild kits can be bought at a fair price. The cost of the rebuild increases significantly if you have to start replacing "hard parts", which these transmissions always need.

Southern Gear Co. - The Standard Transmission Professionals sells transmissions & parts. They were able to rebuild the 5-speed in my F-450 for cheaper than I could buy the parts from them. Plus they had it back to me in less than 24 hours.

Where do you get a brand new T5?

And I had considered rebuilding one. Ive looked into it, and it looks like something I could do.

Many mustang vendors sell the Z model (LMR, Mustangs Unlimited, American Muscle, etc), or at least they used to. It's a Ford Performance part. Not sure about standard T5 new, have to look around, but I think most are rebuilt/reman.

I purchased my T5-Z from Parkway Ford (now closed down) because I knew the parts manager. He sold it to me for cost which was about $1100 (in 2008). I could not buy it the Ford dealership that I worked at because it was not a Ford Racing distributor. I will check with my other parts guy and see what the cost of one is now.

Here ya go: T5 FORD 5.0 $1,750. Brand new. Mike Forte has been around forever, and is a super reliable vendor.

My cost from Ford for a brand new T5-Z (M-7003-Z) is $1897.50 + tax.