3.73 or 3.55 gears

cavero

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I'm in the market for new gears since mine have been whining for 4 years and I can't take it anymore. I've been doing a lot of research on it and it seems like since the gears have worn in with bad pinion depth, I'm going to need new gears to get rid of it. I've got the factory 3.55's on my '06 GT (manual) right now and I figure if I'm going to spend the cash on it, I might as well consider going for something a little more agressive.

4.10's are way too aggressive, so I'm looking at 3.73's.

Anyone make the jump from 3.55 to 3.73? Any drawbacks? How much worse did the gas mileage get? How much more fun is it?

This car is my daily driver and when I do take it on long highway trips I hate stopping for gas, so MPG is a factor. So is noise since the engine will be about ~150 rpm higher at 70-75MPH (did the math). I have the stock exhaust but a CAI and dyno tune. No issues with engine drone (at least I don't notice it over the sound of the damn gear whine).

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Godzirra

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Well I have a coyote. I went from a 3.73 to a 3.55, the 73 is definitely a ton more fun. I'm getting maybe 1mpg better with the 3.55, I plan on putting 4.10s in my car.
 

Redrocket06

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Go to the 3.75's and drive 5-10 mph slower to make up the mpg differnce. You might fine that most people would go to the 4.10 if they had to swap. I like my 3.55's but if I had to change then the 3.73 would be my choice even being built blown and cammed.
 

JCCNY

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I'm assuming your N/A. Did you drive a manual with 4.10's to determine they are "way too aggressive?" Since you have to swap gears, I can see going to 3.73's but it wouldn't be worth it otherwise.

Search is your friend on this topic. Lower geared cars (like 4.10) usually get better mileage around town & worse on the highway. I'm about to go from 3:55 to 4.10's and can't wait!
 

Fullboogie

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I did the opposite - I went from 4:10's to 3:73's and like it a whole lot more. For me (meaning my experience with my car), 4:10's were just too much gear for the highway mileage I put on my car.
 

stkjock

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been shown over and over on this site

4.10s + 28" tall tire is best combo for n/a car for racers

you want mileage - go buy a Fiesta
 

jonw605

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Unless you drive a lot of highway, 3.73's are the way to go. Little better milage for combo driving in my experience and only 1-2 mpg difference in highway. For sure go with the 3.73 and consider 3.90's.
 

JCCNY

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Unless you drive a lot of highway, 3.73's are the way to go. Little better milage for combo driving in my experience and only 1-2 mpg difference in highway. For sure go with the 3.73 and consider 3.90's.
I think you mean 3.73's are the way to go IF you drive a lot on the highway. My Mustangs have never been daily drivers, but I loved 4.10's on the highway in my 04 new edge. Nice acceleration from 40 or 80 MPH!
 

BruceH

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The highway difference isn't very much. 5th gear is .68. 3.55 x .68 is 2.414 final drive ratio, 3.73 = 2.536 and 4.10 = 2.788. The two best combos for lower noise are going to be 3.55 and 4.10.

I've gone from 3.55 to 4.10 to 3.55 to 4.10 to 4.56 to 4.10. Running 4.10 right now. Get the 4.10s. You will not regret it, ever!
 

cavero

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Go to the 3.75's and drive 5-10 mph slower to make up the mpg differnce. You might fine that most people would go to the 4.10 if they had to swap. I like my 3.55's but if I had to change then the 3.73 would be my choice even being built blown and cammed.

Yeah that'd probably help with my speeding record. I go in to court next week.

I'm assuming your N/A. Did you drive a manual with 4.10's to determine they are "way too aggressive?" Since you have to swap gears, I can see going to 3.73's but it wouldn't be worth it otherwise.

Search is your friend on this topic. Lower geared cars (like 4.10) usually get better mileage around town & worse on the highway. I'm about to go from 3:55 to 4.10's and can't wait!

I was trying to say they're way too aggressive for my needs. The car is touchy enough with my dyno tune, 4.10s would just make it awful in stop and go traffic. Plus I do a fair amount of highway milage. Not only on my way to work every day, but also 400 mile stretches to go visit family when it really counts. It can make a difference of when I'm by myself and getting 26mpg or if the wife is with me with all her luggage when I get 23 mpg

been shown over and over on this site

4.10s + 28" tall tire is best combo for n/a car for racers

you want mileage - go buy a Fiesta

I knew someone was gonna say that. Uhhh....no. I'd rather get the focus. But still no.

Btw, I'm not a racer. I don't have that kinda budget

Unless you drive a lot of highway, 3.73's are the way to go. Little better milage for combo driving in my experience and only 1-2 mpg difference in highway. For sure go with the 3.73 and consider 3.90's.

The highway difference isn't very much. 5th gear is .68. 3.55 x .68 is 2.414 final drive ratio, 3.73 = 2.536 and 4.10 = 2.788. The two best combos for lower noise are going to be 3.55 and 4.10.

I've gone from 3.55 to 4.10 to 3.55 to 4.10 to 4.56 to 4.10. Running 4.10 right now. Get the 4.10s. You will not regret it, ever!

Why do you say that those are the best for gear noise? And why did you flip-flop between 3.55's and 4.10's?
 

KITT

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My friend went from 3.55 to 3.73 and I couldn't feel any difference at all. I went from 3.55 to 4.10. I have no problem in traffic all motor and now with it supercharged it's even more fun.
 

BruceH

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Why do you say that those are the best for gear noise? And why did you flip-flop between 3.55's and 4.10's?

It has to do with tooth count on the ring and pinion combination. For whatever reason those particular combos are more forgiving for the installer. It's not hard fact, just opinion but if you search out noisy gear threads 3.73 and 3.90 come up alot.

My car came with 3.55 gears. One of the first mods was 4.10 gears, a supercharger was installed and later more power from the supercharger so it went back to 3.55. Then a TR-6060 went in and the gear ratios in that transmission work alot better with 4.10 vs 3.55 gears. Eventually the supercharger was taken off and 4.56 were installed. The 4.56 gears went from being quiet to making noise after some hard launches on drag radials. The crush sleeve was changed out for a solid spacer but it was too late, the gears remained noisy so 4.10 went back in with a solid pinion spacer.

Almost anyone who has had a TR3650 and 4.10 gears loves the combo, even on the highway.
 

MountainMichael

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cavero,

I went from 3.55 to 3.73 recently on my sc 06 'stang GT with MT. It was a fight getting the gears quiet, but much of that was my fault. It made a noticeable difference in power response with SC.

I find that driving at low power levels is much easier now in heavy stop and go traffic, stop lights, etc. Makes me think 1st gear was too tall with 3.55's but seems perfect with 3.73.

I kinda' have gear envy wondering how 4.10 woulda' been. But it's a tire incinerator now, so it's enough since I don't race.

As for noise issues: 3.73's from FRPP used to be SOLD by FRPP but made offshore and reportedly had some serious problems usually causing noise. New 3.73 gears are made at the Sterling Axle Plant in the US where all (?) the other FRPP 8.8 gears are made. Proper setup should make them quiet IMO - but it's gonna take awhile before many people will believe it and reasonably so because of all the problems with the previous offshore made FRPP 3.73's.

Above is my understanding of it and what Steve at Tousley told me. All parts and packaging supported the assertion that they're made at Sterling in the US now.

If anyone thinks the NEW 3.73's made at Sterling are noisier than 3.55 or 4.10, please post up some specifics/reasoning. My experience with these gears is just one instance; far from establishing a trend so added input would be great.
 
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Silverrider

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I went from 3.31 to 4.10's, love them.. seems like with 4.10's I am always in the sweet spot, cruising in town or on the highway! I have no regrets, but I don't drive on the highway unless I am cruising for fun.. not a dd, out of the two you listed 3.73 for sure.
 

Agent007

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3.31 to 4.10's here with an auto. Absolutely love the difference it made in the car... just don't try to roll race a turbo cobalt SS from 80mph... your car will feel like it is sitting still LOL
 

sethah

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So what would be the best compromise for road course and drag strip? There is a great road course close to where i live i want to go to but i still want to have fun in 1/4. I currently have 3.55 & was thinkin bout getting 3.73.

Sent from my SAMSUNG-SGH-I897 using Tapatalk 2
 

BleedinBlue

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My friend went from 3.55 to 3.73 and I couldn't feel any difference at all.

This. There's not enough of a difference between 3.55 to 3.73 to justify the swap IMO. If you've already modded to the point that it's "all there is left to do" then fine, but otherwise I wouldn't change them. (And I'm in that boat, I'm sticking with 3.55's unless I want 4.10's after a blower)
 

3VPOWA

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If you're going to open it up to fix it and don't really care for a drastic difference in acceleration, then I say go with the 3.73's. Now with that said, I wish I would have installed my 4.10's sooner. I had them since last August but just got around to having them put in a few weeks ago.

The gas mileage with my car has always been terrible, even when stock. The best I ever got out of it was 23 mpg on a three hour trip from Austin back to my hometown. I average around 16-17 mpg after the gear install on the highway. Before the gears I was averaging 18 mpg on the highway with 3.55's doing ~70-75.
 

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