Gear Tech for modulars

blackfang

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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 can’t rev past 5500 RPMs. 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.
 

Outlaw97GT

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Im getting my rear-end rebuilt next week, due to my ****** wheel bearing going out a month before
schedule.....lol I knew it was bad, but I wanted to wait till tax time.

Im gonna ditch the 3.08's for some 4.10's while its apart. All new bearings and reclutching the diff.
Can't wait...... :banana:
 

STNG_96

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Im currently a poor college student, so gears are not exactly too far up on my list right now, maybe in a few years when I'm an engineer ;D
 

JerZeyStangz

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4.10's are defiantly on my list but when they get installed in the future...im defiantly going to need a speedCal right?!?
 

blackfang

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Speedcal is the way to go. That way you can have it accurate and if you swap rims and change sizes it will compensate.

I am thinking of going 4.56's if I do not install the nitrous kit.
 

DropTopPony

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STNG_96 said:
Im currently a poor college student, so gears are not exactly too far up on my list right now, maybe in a few years when I'm an engineer ;D
come on get a paper route or something :dancing6:
gears don't cost that much.
I was a bouncer in a titty bar while i was in college. I didn't do it for the money :rockyou:
 

Outlaw97GT

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Well I drove up to Waco to see my Pops. While I was in Waco I went to 50resto and got all my stuff ( FRPP 4.10 ,
bearing kit, diff reclutch kit, royal purple oil)
Hopefully I can get it in the shop monday........ :banana:
 

tomustang

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My 3.73's were adequate for street use in my 98 GT, I failry liked them, I'd say it was a great 'all around' gear
 

DropTopPony

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blackfang said:
I got rid of my 3.73's for 4.10's in my 97 GT
was that a big enough difference to feel anything? I have 3.73's and should have swapped to 4.10's when i put in the new diff. :(
 

spdracer

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now i am definatly going for the 4.10's... hopeing to have them in within the next month.. shoud really wake things up/.
 

blackfang

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DropTopPony said:
blackfang said:
I got rid of my 3.73's for 4.10's in my 97 GT
was that a big enough difference to feel anything? I have 3.73's and should have swapped to 4.10's when i put in the new diff.  :(
I noticed a difference. Granted it wasn't like that of 3.27's to 4.10's but it was felt.
 

97vertstang

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my buddy use to own my car and he installed 3.73s on it, if it were me i would have gone 4.10s or 4.30s. 3.27s to 3.73 is .46 difference.from 3.73 to 4.10s is .37 diffrence s i have been debating if i should invest on going 4.10s since i already got 3.73s but then again i could go all the way to 4.30s.but then i need axles and probably a stronger carrier.with overdrives i personally believe 3.73s is a waste of money 4.10s or higher, unless going with a power adder.
 

ALITL8

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ive got the Motive 3.90's and love them... great all around ratio. i was told 3.73's to 4.10's by a number of people so i just picked a number in between :dunno: the gears are great and really added some pep to the car ;D
 

Iceman12

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I run 3.73's, I love them. I feel like that is plenty of gear, but of course I've never felt anything higher, so who knows. I do know that I feel like my 1st gear is pretty darn short with my t-45 and the 3.73's, and i wonder if it would have been down right annoyingly short if i had gone with 4.10's or more. I'm still in major indesition about my car, I know i want a t-56 in the car, which has a longer 1st gear, but I don't know if I'm gunna go with a blower, or turn the car into a high RPM N/A screamer. either way I know i want some Mach 1/03 CObra heads, intake, and cams, but If I put a Procharger on too, I wouldn't want more gear, but if I leave it like that, I would definatly want more gear.

Sorry, that turned into a kind of rant about my car, didn't mean for a big post, just sort of thinking out loud........in written form......typing form..... :-X
 

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