Gear ratio change

[Josmen]

alright, I have a 96' gt, 5spd that has some worn out 3.27 gears in the 8.8 rearend. If put in 3.55 gears what kind of difference would I be looking at in driving characteristics. From what I understand I will lose some top end but it will pick up a little faster off the line. Not quite sure how much I will lose and am curious. Thanks

Dan

 

[BurningRubber]

I dont have gears in my Mustang yet, but I can tell you 3.27 to 3.55 would be pointless.

3.73 is the lowest you should go. Pretty much everyone will tell you 4.10's and no less. But 3.73's will offer a decent improvment (according to all that have them) and still cruise nicely down the highway. Keep in mind you will tach higher going down the highway than with stock gears.

 

[goshia]

3.55 will help very little and you wound notice a big change in performance, once you go to 3.73's you will be running at higher rmp's that you will notice during highway driving. then at 4.10 the rpm increase could get to a level that might make you a littel nuts on a long highway drive.

check out: http://www.weather-check.com/3_73_gear_&_pinion.htm

 

[Josmen]

Well, the 3.27 gears are wearing bad and starting to howl, and I have the 3.55 gears for free and not a lot of cash to buy new ones anyways. So just to get it back on the road I think I might go with the 3.55 gears. Thanks for the info!

Dan

 

[CobraRed_96_GT]

well the install, if ur paying, costs more than the gears so....

 

[Josmen]

A guy at a shop behind my work does gears on the side, so I am getting them put in for $100 so it isn't too bad.

Dan

 

[Mel96GT]

Well, the 3.27 gears are wearing bad and starting to howl, and I have the 3.55 gears for free and not a lot of cash to buy new ones anyways. So just to get it back on the road I think I might go with the 3.55 gears. Thanks for the info!

Dan

For that cheap go for it! Anything is better than those 3.27's. The 3.55's are actually perfect with the stock NPI cams, IMHO, since the stock NPI engine redlines at 4500 rpm and it is slightly torquier at low rpm's than the PI engine. With 3.27's I would do 70 at 2100 rpm's, where now with 3.55's I do 70 at 2300 rpm's.

You will notice improved acceleration (at least I did) with 3.55's, and your gas mileage and top end will be the same. In fact, a friend of mine started installing 3.55's in some of the Crown Victoria cop cars he services and the guys love them since the acceleration is improved without affecting top end. Don't forget to buy a new 3.55 speedo gear for the tranny. I don't think you will be too disappointed. Let us know how you like them.

 

[the98stang]

4.10s for NA cars

3.73s for turbo/SC/n2o

You'll spin all day long with a KB 1.7 SC and 4.10's

 

[MBDiagMan]

Going to a lower gear (higher numerically) will likely INCREASE your top speed, not lower it. This is due to the torque multiplication allowing the engine to overcome the wind resistance and other factors that fight against faster speed.

These cars have overdrive final ratios and high RPM torque peaks. 4.10's are not unreasonable gears, even for highway driving.

 

[stangGT97]

For that cheap go for it! Anything is better than those 3.27's. The 3.55's are actually perfect with the stock NPI cams, IMHO, since the stock NPI engine redlines at 4500 rpm and it is slightly torquier at low rpm's than the PI engine. With 3.27's I would do 70 at 2100 rpm's, where now with 3.55's I do 70 at 2300 rpm's.

You will notice improved acceleration (at least I did) with 3.55's, and your gas mileage and top end will be the same. In fact, a friend of mine started installing 3.55's in some of the Crown Victoria cop cars he services and the guys love them since the acceleration is improved without affecting top end. Don't forget to buy a new 3.55 speedo gear for the tranny. I don't think you will be too disappointed. Let us know how you like them.

yep... I'm not sure how much the 3.55s helped me since I didn't install them but they aren't too bad for my stock heads and cams and the gas mileage on the highway is still pretty good. If the gears are free and install is cheap, then you may as well go for it. Don't forget your car will feel a lot tighter on WOT runs with a freshly built rear so thats one bonus of getting these gears put in.

 

[merc123]

Going to a lower gear (higher numerically) will likely INCREASE your top speed, not lower it. This is due to the torque multiplication allowing the engine to overcome the wind resistance and other factors that fight against faster speed.

These cars have overdrive final ratios and high RPM torque peaks. 4.10's are not unreasonable gears, even for highway driving.

I hope your joking about top speeds...that's the math.

Engine RPM: 6200
Vehicle Speed: 186.755285063091
Read End Gear: 3.73

Engine RPM: 6200
Vehicle Speed: 213.026670729459
Read End Gear: 3.27

 

[Mel96GT]

I hope your joking about top speeds...that's the math.

Engine RPM: 6200
Vehicle Speed: 186.755285063091
Read End Gear: 3.73

Engine RPM: 6200
Vehicle Speed: 213.026670729459
Read End Gear: 3.27

That math only works if the car is in a vacuum, i.e. no atmosphere. The reality is wind resistance which is a function of the square of the speed. That is what MBDiagMan was alluding to. It basically takes twice the energy to go 100 mph compared to 70 mph because of wind resistance. That is where the torque multiplication comes in with lower gears. A Mustang with 3.27's will NEVER get to 213 mph without a heavily modded engine and aerodynamics.

 

[stangGT97]

That math only works if the car is in a vacuum, i.e. no atmosphere. The reality is wind resistance which is a function of the square of the speed. That is what MBDiagMan was alluding to. It basically takes twice the energy to go 100 mph compared to 70 mph because of wind resistance. That is where the torque multiplication comes in with lower gears. A Mustang with 3.27's will NEVER get to 213 mph without a heavily modded engine and aerodynamics.

The max theoretical speed of a car will always decrease as it gets geared lower (ie, going from 3.27 to 4.10). At the same time, however, the max attainable speed will increase due to the extra torque multiplication giving your car the ability the extra power to overcome wind resistance.

 

[jstreet0204]

The max theoretical speed of a car will always decrease as it gets geared lower (ie, going from 3.27 to 4.10). At the same time, however, the max attainable speed will increase due to the extra torque multiplication giving your car the ability the extra power to overcome wind resistance.

What? You mean he your car wouldn't go 213mph stock? You better get it check out. You must have gotten a lemon.

 

[steveb24]

that math looks good and all, but remember we are on earth, and are not driving ferari's

 

[mrvax]

Go with 3.73's or 4.10's and never look back. It's that simple. Your car will thank you for it.

 

[stangGT97]

What? You mean he your car wouldn't go 213mph stock? You better get it check out. You must have gotten a lemon.

My car has the NPI speed limiter mod

Did my reasoning not make sense?

 

[jstreet0204]

My car has the NPI speed limiter mod

Did my reasoning not make sense?

Yeah, I understand. I put 4.10's in as a speed limiter. 200mph + was just a little too fast for me. I figured if I could only do 180 it would be a little safer

 

[speedfreak98r]

How fast can one go with 4.10s with a bolt on NPI car..I've been wondering about top end/gear ratios..Maybe a sticky on the subject?

 

[stangGT97]

Yeah, I understand. I put 4.10's in as a speed limiter. 200mph + was just a little too fast for me. I figured if I could only do 180 it would be a little safer

Yeah. In all honesty, with 3.55s my car does not want to go past like 4000ish in 5th gear (tried once, it didnt work). All I get is a roaring engine and a constant speed