Gear info
 

Probably the most frequently asked question on every mustang message board, gears are not debatable. 4.10s minimum on a daily driven 4.6L N/A mustang. I’ll get to why in a minute but to realize why there is no debate, we must first look at what gears do. Gears live in the rearend, bolted to the pumpkin and driven by the driveshaft. The job of gears is to multiply the engine’s torque. So with a 250 TQ engine with 4.10 gears, your multiplied torque will be 1025. You might be thinking, “Why the hell do we need that much torque?” Well, the truth is, without a multiplication of torque, our cars will not move. For some visual information about gears and differentials, go here. Most stock mustangs have 3.27 gears from the factory. I have no idea why Ford put these gears in our cars because they’re awful.

Despite what some “experts” might tell you, gears will not decrease your top speed in a mustang; in fact, they’ll probably increase it. If you were to top out your car with 3.27 gears, you’ll notice that the power just stops when you shift to 5th gear. This is because you are not in the car’s powerband to pull the car up to higher speeds. Not only will steeper gears allow you to pull quicker but also they’ll keep you in your powerband which will, in turn, enable you to pull in 5th gear; something you could NOT do before. Other experts claim that you will lose gas mileage due to the higher RPMs that your car will now be traveling at on the highway. In reality, you’ll lose maybe 1 MPG at best. By far, the biggest misconception out there is that 4.10s are “too much gear” for a car. These people that tell you this are morons. Those people are stuck in the pushrod days where the cars power isn't past 5500 RPMs unless it's built. Our cars rev to 6000 RPMs for a SOHC and 7000 RPMs for a DOHC. Our torque comes on later than the pushrods, hence the need for the steeper gears. Sure, there are instances where you might want to get a different gear ratio if you have a poweradder or are a drag only car, but be it Auto-Xer, Open Tracker or Drag Racer, do NOT get less than 4.10 gears for a daily driven N/A mustang. For those who want to play around with gear ratios, go here.

The recommended brands for gears are FMS, FRPP and Motive. FMS and FRPP are the same gears however. Ford has two markets for the same rearend; one is the SUV market and one is the Mustang market. The SUV market isn’t as high performance and not as willing to spend the big bucks for items like the Mustang market is, so they take the gears they make and label one FMS and one FRPP even though they’re the exact same thing. In the end, just get whatever is the cheapest. I recommend getting a shop to do the install as this is a pretty complex thing to do. The install kit depends on how many miles you have on your car. If you have more than 35k miles, I recommend stage 2. If you have more than 75k miles, I recommend stage 3.

nm...

Sry dude but some of ur info is way off. Pushrods not being able to rev past 5500rpms. LOL...what planet are you on? I take my daily drivin pushrod car higher than ur 6k. :funny:

Ya a 3.27 gear does suck for a N/A mod motor but slap a turbo on there and you'll be in another world. :)

not only that but 2v's tend to fall on their faces up top. steeper gears do mean lower mileage and lower top speed. althought when it comes to 3.73's and 4.10s i think the cruise rpm differential is only 200 r's between the two. that tid bit is informative but still a little off.

Some are forgetting the entire point. How many daily driven poeople want to spend 6k to slap a turbo on their daily driven Mustang GT to compensate for the 3.27's, come on now?

Actually a steeper gears increases top speed and many are seeing 24-25 mpg with them. I have gotten 25mpg with 4.30's. You can increase top speed because the gears allow 4th and you can actually pull in 5th gear and it keeps the cars in their powerbands.

How many stock longblock 5.0's make more power past 5500? The pushrod 5.0 in stock form doesnt make power after 5500 to justify a 4.30 gear or 4.56 gear for daily drivers. The 2V and 4V make their power all after 4500 rpm. Let me reword it then.

What year?

Gears are definitely a must. Good info, except the pushrods comment ;) I shift my pushrod motor between 6800 and 7200, with hydraulic lifters no less :devil:

I am talking about a stock pushrod 5.0, stock heads, valvetrain, etc. I am sure if you upgrade the heads/cam and intake it will make more power above 5500.

Gear selection should be based on rpm vs. peak hp at the lights. You want to gear your car so you are 200-400 rpm above peak hp at the finish line for max et. You can't say a 4.10 or 3.73 or any gear is best until this criteria is met.

okayyyy, now that you reworded ur *ahem* statement.......Yes n/a, stock headed, cam and intake 5ltrs do not make power past 5500...let alone a little after 5000 really. I shifted my car when it was stock at 5500. :rock:

Also a change of tire can affect what rpm and peak hp is at when you cross the traps. Also not every person drag races their cars, but surely wants more bang for their buck. So should we not recommend a gear swap until they drag race and do the research on where there peak hp is and at what rpm?

If you are not wanting more acceleration and/or don't plan to drag race, then why change gears at all. The factory gears will give best mpg and engine longevity. Best bang then is to keep it stock. If you want to sacrifice et then go ahead and guess the gear and be done.

You can waste a lot of money guessing the gear to install if you are wanting maximum acceleration. Even when you know peak hp, max rpm, tire diameter, future mods, projected mph, etc. you can calculate the wrong gear. You will get closer to optimiun though. But those are minimum things you should know before selecting a gear to make a reasonable selection. Even after you've made passes at the track you must know peak hp. That's only attainable from the manufacturer or dyno testing.

The info I orginally gave was the end result you are trying to achieve for maximum acceleration. Not the way to get there.

That is what I am saying, if I want more ump from the car, then gears is a great route. However for your average person or the novice drag racver that goes maybe once every few months trying to figure out peak hp@ what rpm isn't the best and most feasible route because it may take 10+ trips down the 1320 to drive the car right to even get that data.

Actually the aftermarket gears will not do any more damage to the engine than stockers. It has been debated and proven. This is why...Load is based on air flow.It flows the same level of air at each rpm no matter what gear is in it.Gearing just gets you thru the rpm band faster.If anything its less stress on the rotating assembly because its not lugging. MPG has also been proven to be increased as well because 4th and 5th gears are more usable. Some have even done their own testing and gotten almost 26 mpg with 4.10's.

Sure gears will give you more hump! If selected correctly. Didn't say anything about 10 trips to the track. Just one trip to the dyno is all it takes to determine peak hp. 10 trips to the track and you still won't know peak hp.

Didn't say anything about damage to the engine from gears. I said longevity! Your engine will turn more rpm with lower gearing and over time will produce more wear. Did not address the issue of mpg. That's another issue. Aren't we talking acceleration? But yes, if properly selected, gearing will improve mpg too. The factory has done a pretty good job in that area though under average driving conditions.

MPG debate-
Again that is incorrect on the gears and engine longevity. I have had this same debate elsewhere and Tim barth who owns and runs Modular PowerHouse even stated that a steeper gear in no way will cause an engine to not last as long compared to the stockers. The gears will not affect the load on the engine.

I am done with the thread, I gave advice and info proven by one of the top notch and best modular engine builder out there. :chug:

2001.

Don't fear the gear.