Should i get 3.90's
 

Hey guys I have been thinking about gears for a while. First off i don't get how they help if they lower the speed your at at different RPM's I read about some guy able to do 30mph in 5th gear. Does this not lower your top speed and do you not hit your rev limiter all the time? Next I do some highway driving but not a whole lot but 4.10's are too much for me i'm positive of that so how bout those 3.90"s? LMK

I can't explain to you how the gears work, but I will tell you that I was in the same boat as you. And I ordered my 3.90's Monday. I do a good amount of highway driving too, and I think with the 3.90's it is perfect if you do highway driving. It's better than 3.73, but not as tall as 4.10. I posted a link in another thread of a guy that filmed and commentated while driving his stang with 4.10 gears. In 5th gear, he was doing 70mph at about 2,600RPM. And 80mph around 3kRPM. But when do you ever really drive above 80 while cruising, unless you are racing. It also showed him doing 135mph all the way through 5th at about 5kRPM. If anything, it might keep you from speeding, IMO. I had a 5.0 with 3.73's and it makes a huge SOTP difference. I think everyone with gears will say they have no regrets, other than maybe getter too small a gear.

IF your doing a bit of hiway driving the 3.90 gears are a nice compromise. You will not be dissapointed.

Taller gears will lower your top speed. Who needs to go 150mph anyway?

By raising the number of the gears in the back you are increasing the torque multiplier to the wheels making it easier for the engine to turn the wheels which allows you to "rev up" quicker. Now granted, RPM for RPM you will see a slower acceleration... but the increased torque multiplier factor by your gears more then compensates for this.

Grr... I hate explaining something like this. How's this... if you go from 1,000 to 4,000 RPMs with a stock gear set you'll be going about 30 mph in first gear... with the 3.90's you may only be going 25 or so mph which is slower... but you will have been able to get from 1,000 to 4,000 rpms much faster making the acceleration better.

Now one things about the 3.90's... Ford racing doesn't make that gear set... you have to get the others (Mopar is it??)... from what I've heard they're just as good quality wise, but the install is a bit trickier... apparently any monkey with a wrench can put in the Ford gears without noise but the other gear set requires a bit more finess...

Just think of it as a bike with multiple speeds. The bigger the crank gear on the bike the easier it will be for you to take off. Its like that for cars. So if you want to get your car to take off quicker get a bigger gear. You wont be hitting the rev limiter if you change gears before you reach it. If you have a automatic then it all has to do with pressure build up and stuff.

If you have the proper install kit with shims there is NO difference installing any ratio or any brand. Any gear you choose will require the backlash adjusted and the pinion depth set to have the proper teeth contact. A gear install can be performed by most competent technicians within 2-3 hours with the proper tools (magnetic dial indicator and pinion puller and torque wrench) Don't be scared of a 3.90 just because Ford motorsports doesn't offer it.

3.90 is good. question for you is, will you be using n2o or turbo/super charger. If that is the case then go with 3.73 gears. otherwise go with the 3.90.

Good luck man.

One other thing... most people notice a top speed increase with a higher gear set...

On a mostly stock GT... the limiting factor for speed is not the rev limiter in 5th gear, it's actually power. By lowering the gears you're getting up to your top speed at a higher RPM in 5th gear and we know in our cars the higher RPMs are more powerful allowing us to go faster. While the theory of higher gears loses top speed is true in a vacuum, in real life with wind resistance, you won't see a drop, you might even see a gain!

mine are going in, in a few weeks (3.90) you will be so happy you got them. the reason ford doesnt make them is that they are so close to 4.10s its not worth it to them but a lot more are going that route now i wont be surprise if ford makes them soon. i have an auto and do 60-70 miles a day all highway and i chose the 3.90s. its a nice gear and at 70 mph on my auto the car will be at 2500 rpm`s.

Someone also told me if u dont have a programer to get one before u get the gears

No, you dont have too, as you can get a 90 dollar speedcal to fix your speedo just the same. You will love the new gears, but they are pricey to be all said and done, so just be prepared. It is all worth it though. You can get a speedcal from www.brothersperformance.com or from www.dallasmustang.com.

My gears and swap cost me around $250 total :) That's without any sort of speedcal though and I just recently got the programmer for other things as well.

Granted, I had a friend of mine help me install the gears :)

confusion between higher and lower gear ratios
 

I noticed that people refer to 3.90 and 4.10 as being higher gears. this is not the case. While they maybe numericaly higher in actuality it is a lower gear ratio. the lower the number the higher or taller the gearing is the higher the number the lower the gear ratio is. and in actuality what is realy happening is lets say you have 2.73:1 what this means is that the drive shaft has to turn 2.73 times to make the tires do on full revolution. With 3.90:1 the drive shaft has to turn 3.9 times to make the tires do on full revolution Thus making the engine have to rev higher to go the same speed but making it allot eiser for the motor becuase of the greater tourque multipucation