how much do 4.10's differ from 3.73's?

It would be very difficult to use a comparision between 2 different cars with the 4.10s and 3.73s. The cars would most likely have different modifications, definitely have different driving styles, and different commutes. However you can calculate the difference in RPM between the two. I don't know if you have 3.55 or 3.31 gears, but if you have 3.55 gears and want to go to 4.10, take your rpm at a set speed, divide it by 3.55 and multiply it by 4.1. If you have 3.55 gears, then it would not be worth it to make the small jump to 3.73s. I think the reason most avoid 3.90 gears is that Motive makes them and some have had problems with Motives whining. I think most people are very happy with 4.10 gears.

I am on my 3:rd set of 4:10's, and I can't get rid of the whine. only paid labor and parts for one, the shop really tried to please me but they all seem to whine at least in my car. The first two sets were FRPP gears and they were really noisy. The ones I ahve now are Youkon which are actually 4:11, and they are better but still whine too much for me. I would hate to give up the acceleration you gain with the 4:10/11 gears.

#1stangFAN said:

i have an auto, pretty sure 3.31

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Yup, autos are all 3.31, so a 3.73 would be worthwhile for you. It sucks that Casey4s is having problems with his, but most people are happy with them, especially the FRPP ones.

I had 3.55s in mine and switched to 4.10s and love em. Absolutely no whining at all and the gas really isnt that bad, maybe a little worse but that is only if you have a lead foot all the time. 4.10s all the way

Look at the tag on your rear end. It will tell you what gear ratio you have. Go for the FRPP 4.10a gears. Any whining you get is due to a bad install not the gears.

I have the stock 3.31's, man trans, susp and tires (17's). If I went 4.10 or 3.73, I'd assume traction from a dig would leave me spinning in first and second. You have an auto, but still if you get some wider tires, better suspension, the 4.10's would be good.

2007Vert said:

Look at the tag on your rear end. It will tell you what gear ratio you have. Go for the FRPP 4.10a gears. Any whining you get is due to a bad install not the gears.

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I totaly agree, I think the tech that did the installs on my car has done something wrong. I need to just lose the money and go to another installer in my case.

Gas mileage doesn't change much (if at all) around town when going from 3.31's to 4.10's. This because gears are a torque multiplier, so to accelerate your car from a stop or low speeds, you'll need less throttle position to accelerate at the same rate of speed with steeper gears (such as the 4.10's). Less throttle position means less fuel consumed.

At highway speeds, you may see a very small drop in fuel economy at a steady state cruise with the steeper gears as you are turning a few hundred more rpm's. However, the OP says he doesn't drive on the highway much, so steeper gears would be ideal.

Me? I have 4.10's in my supercharged '07 GT and love them (had 4.30's in my 03 Mach 1). FRPP's and no whining at all.

I went 4.10s in my auto and I've never looked back! They've been in for nearly 60K miles and I've never had an issue! I run a taller rear tire than most (29.2") others on the street. The 4.10s allow me to do that and not lose much performance. I run the OEM 235/50-18 in the winter and 26.5" MTs to and from the track and the 4.10s are still very easy to live with out on the open highway at 80 MPH If you're thinking between 3.73s and 4.10s, do the 4.10s as you may do the 3.73s then wish you went that one extra step.

Casey4s said:

I totaly agree, I think the tech that did the installs on my car has done something wrong. I need to just lose the money and go to another installer in my case.

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I don't think that's it. Same installer did my FRRP gear install. Perhaps there is an issue other than just the ring and pinion that is causing the whine...

gears

My 2006 GT has 4.10's and is an auto....makes the car jump.....prev owner got about 22 mpg but I get 16 mpg....I can't keep my foot out cause its so much fun.......

#1stangFAN said:

thanks, best reply so far that summed the majority of things up besides getting someone with some actual MPG numbers to post.

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When my car was 100% stock, but with 4.10's, I was getting about 26-7 mpg on the highway at 60 mph on cruise control. Dropped to about 23-4 mpg at 70 mph on cruise control.

4.10's, big stall converter, custom tuning, and Vortech V2 supercharger: I get 23-4 mpg on the highway at 60 mph, and 19-20 mpg at 70 mph. The drop from pre-blower is mostly because the stall converter and those speeds keep surging a bit to induce boost from the supercharger.

Around town, I got about 15-16 mpg with the 4.10's before the blower went on, but I'm a lead foot. With the blower, I'm down to about 11-12 mpg, but I drive like John Force every chance I get!

I'm kinda in the same boat the OP is. I want to get new gears, (I've got the stock 3.55's), but I don't want to kill my gas mileage. I drive on the freeway every day. So I'm leaning towards the 3.73's because I think the 4.10's will be too steep.

I think it's going to be hard to find someone that can really give you an apples-to-apples comparison, because even when you just change your gears and do nothing else, the tendency is going to be to drive the car harder to feel the difference.

I recently went from the stock aribox, to a Bullitt CAI and Predator tune, and I'm trying to see if there is much of a fuel mileage difference. But I can't really, because I constantly find myself driving the car harder because the throttle response is so much better now.

410

"Around town, I got about 15-16 mpg with the 4.10's before the blower went on, but I'm a lead foot. With the blower, I'm down to about 11-12 mpg, but I drive like John Force every chance I get!"


yep...me too!

#1stangFAN said:

...can someone please tell me what a stall converter is? i know, totally noob question but i just dont get them and i didnt want to make a new thread

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A stall converter is a torque converter with a higher rpm launch ability for an automatic transmission. Guys with manual transmissions can rev up their cars really high and drop the clutch for a super hard launch. Automatics don't have that luxury with the stock torque converter, so getting a converter that revs higher at launch is the way to go for much quicker starts.

The stock torque converter flashes to about 2300 rpm's if you mash the gas pedal. A stall converter that flashes to about 3000 to 3200 rpm's is a good street/strip upgrade, but our heavy cars really need a bit more to really launch hard. 3400 to 3600 rpm converters are really about perfect for entertaining street/strip cars, while maintaining decent fuel economy. I bought one rated for 3600 rpm's (in a stock GT). Once you start adding horsepower, though, the rpm's that it flashes it will go up. So, with just a CAI & tune, my was flashing to 3800 rpm's. Added the supercharger and it now flashes to 4800 rpm's making for a very aggressive launch (just like a guy with a manual trans revving to 4800 rpm's and dumping the clutch).

Keep in mind that if you take off with partial throttle, the car won't rev as high. The flash speeds I mentioned above are only at wide open throttle. So, the car will feel normal at light throttle, but is a beast when you mash the pedal to the floor. Wide open throttle shifts are better, too, as rpm's never fall below the flash speed (unlike a manual trans when you lift off the gas to shift and lose rpm's - and boost with a blower/turbo).

To preserve fuel economy, select a stall converter with a lock-up feature. The factory torque converter locks up in 4th and 5th gears (with an internal clutch in the converter) to get better mileage at highway speeds. Low gears don't need the lock-up as you want the converter loose to rev higher for better acceleration. Too loose all the time, though, generates heat which is harder on the trans. So, a bigger trans cooler is a great idea with bigger stall speeds.

Hope this info gets you started. Anyone with an automatic who drag races or wants a more aggressive daily driver should get an aftermarket stall converter. Mine dropped 3 tenths of a second off my 60', 330', and 1/8 mile ET's at the dragstrip and made the car so much funner to drive. Got more performance gain from the converter than the 4.10 gears (and for about the same money).