3.73 gears

[babbage]

Anyone running 3.73's? I'm worried that the 4.10 gears with stock tires will have too high rpms.

What are your RPM's at 80 Miles per hour with stock tires and 4.10's installed?? Mileage?

I planned on getting 17" police HD Steelies for winter and drag strip times (Good year Ultra Grips), so with 3.73's my effective RAR will be close to 4.10's anyway.

[sd8683]

Get the 4:10's........ It's only a few hundred rpm's higher than the 3:55's........ There will be a very minimal gain over the stock gear's with 3:73's...... Bottom line it's not worth it.

Sean

[RoyLPita]

I know Juno has them.

[sd8683]

I know Juno has them.

I beleive a few member's have them........ I think vicsevilbrother has them........ But IMO it's not worth it.

[fastblackmerc]

As stated 3.73's won't give you anything... at least not enough to notice. Go with 4.10's, you'll see about a 200RPM increase at speed and you'll lose about 1MPG.

The grin on your face will be priceless.

[babbage]

What is the rpm at 80 with stock size tires WITH 4.10's

[Wires]

For any speed, your RPM with any gear other than stock is newgear divided by stockgear (3.55) multiplied by that RPM.

At 80 MPH: (stock tires)
Stock gear (3.55) is about 2400 RPM (I think this is correct)
RPM with 3.73 is 3.73/3.55 multiplied by that, for 2520 RPM
RPM with 4.10 is 4.1/3.55 multiplied by that, for 2770 RPM
RPM with 4.30 is 4.3/3.55 multiplied by that, for 2900 RPM
(numbers have been rounded slightly)

Regardless of my stock RPM being right or not for 80 MPH, your RPM with 4.10 will be about 15 percent higher at any given speed. Your RPM will be about 5 percent higher with 3.73, and 20 percent higher with 4.30s.



Most folks are happy with 4.10, or wish they had gone larger. (some have gone larger)

[RF Overlord]

babbage, listen to the advice you've been given ^^^

Many of us have been here for a long time and it's been determined that 4.10 is the best overall compromise of improvement/fuel economy.

Unless you can either do the whole job yourself, or you can get a WICKED good deal on the install, going up 1 step is not worth the time or the money.

[fastblackmerc]

For any speed, your RPM with any gear other than stock is newgear divided by stockgear (3.55) multiplied by that RPM.

At 80 MPH: (stock tires)
Stock gear (3.55) is about 2400 RPM (I think this is correct)
RPM with 3.73 is 3.73/3.55 multiplied by that, for 2520 RPM
RPM with 4.10 is 4.1/3.55 multiplied by that, for 2770 RPM
RPM with 4.30 is 4.3/3.55 multiplied by that, for 2900 RPM
(numbers have been rounded slightly)

Regardless of my stock RPM being right or not for 80 MPH, your RPM with 4.10 will be about 15 percent higher at any given speed. Your RPM will be about 5 percent higher with 3.73, and 20 percent higher with 4.30s.



Most folks are happy with 4.10, or wish they had gone larger. (some have gone larger)

Some have gone to 4.56's and then gone back to 4.10's.

[Vortech347]

I've delt with ratio's from 2.73's to 4.30's in my personal cars.

Marauders LOVE a 4.10-4.30.

3.73's Do help (anything helps) BUT I deeply regretted not having 4.10's. Only reason I did 3.73's was they were free and I had the time to install them myself. The next time around I put in 4.10's. Now I wish I had 4.30's like our Cobra.

Also mpg wise. I got around 280-290 a tank with 3.73's. With the 4.10's I get 300! even more if its all freeway. (when the light comes on)

[mgmsleeper]

not to steal ur thread but jus to piggy back on this for a sec im looking for gears and info i heard from stock MGM gears to 3.73 gears there is a difference but not from MM to 3.73 i also was told 4:10s give you no top end speed unless youre SC, turbo, etc...

so to bring this thread together n help us both can any one add to this tell some more info on 3.73 vs 4.10 with MGM and MM

...thanks

[sd8683]

not to steal ur thread but jus to piggy back on this for a sec im looking for gears and info i heard from stock MGM gears to 3.73 gears there is a difference but not from MM to 3.73 i also was told 4:10s give you no top end speed unless youre SC, turbo, etc...

so to bring this thread together n help us both can any one add to this tell some more info on 3.73 vs 4.10 with MGM and MM

...thanks

Well........ I beleieve the stock gear ratio in a MGM is 2:73 ( I could be wrong and often am) So going from 2:73 to 3:73 would be a drastic differance....... Unlike the stock MM gear ratio is which is 3:55

[RF Overlord]

sd8683 has it exactly right, with one addition...if you have the HPP on your car, then the RAR is 3.27. Even so, going from there to 3.73 is 2 steps and is very noticeable. Remember, too, that a stock MGM has 16" wheels (17" w/HPP), so 3.73 on a Crown Vic/GM is like 4.10 on a Marauder (with 18" wheels stock).

[SC Cheesehead]

not to steal ur thread but jus to piggy back on this for a sec im looking for gears and info i heard from stock MGM gears to 3.73 gears there is a difference but not from MM to 3.73 i also was told 4:10s give you no top end speed unless youre SC, turbo, etc...

so to bring this thread together n help us both can any one add to this tell some more info on 3.73 vs 4.10 with MGM and MM

...thanks

Gears, as such don't "add" or "reduce" speed, taller gears, such as 4.10's will improve low to midrange responsiveness at slightly higher RPM's.

Going from the stock 2.73 to a 3.73 ratio on a MGM results in a 36.6% change; going from 3.55s to 3.73's in a MM gives a 5% change whereas going to 4.10s will give you a 15% change in ratio.

Also, with gear swaps in MGM and MMs, keep in mind that the MGM is fitted with smaller diameter tires than the MM, so you're not looking at a direct comparison between the two vehicles. If you go from stock 16 inchers to 22 inch wheels om the MGM, the effective improvement drops off.

[RF Overlord]

^^^what Rex said^^^

Why is it the first thing a young person asks is "how fast will it go?". Installing a higher numerical gear ratio is for launching the car, which is fairly heavy, not for cruising the highways at ridiculously illegal speeds.

[Vortech347]

I dunno, Thats kinda what I got the MM For....The illegal speed cruising...

LOL

[mgmsleeper]

well im running the MM wheels with the OEM tires. and let the HP and City PD tell it im always "just crusing" at ridiculously illegal speeds along with my ridiculously illegal tint. so with the MM wheels to keep from dropping off the improvement is it best to go 3.73 or 4.10?

[babbage]

I can get a set of Gears installed for $260 cash, new crush sleeve and bearing kit etc. Very good technician.

I already have (i own it) a 3.73 (FRPP N gears) ring and pinon, plus I have a 28 spline traction lock with carbon fiber clutches (Reinhart)

The idea was that I'd have the 18" tires spinning at 3.73 ratio for summer and what not. Then put 17's on for winter and drags and such (which would make my effective RAR close to 4.10)

Anyone ever try a 3.90 gear set?

Also I find it hard to believe that the mileage went UP from 280 miles per tank with a 3.73 to 300 miles per tank with 4.10's

Do the 17" HD police steelies (which are cheap and tough) fit on an MM ok? Wanted to get these for Winter. Perhaps RayJay will sell me his. :bows:

Also since the MM is 03 and 04 there is no VSS or speedo gear to change correct? It's just programming.

[sd8683]

Also I find it hard to believe that the mileage went UP from 280 miles per tank with a 3.73 to 300 miles per tank with 4.10's.... I think Vortech347 is referring to 2 differant cars...... One MM he had 3:73's and another which he has now has 4:10's..... Sorry for speaking for you Vortech...... Atleast I hope I got the info right lol

Do the 17" HD police steelies (which are cheap and tough) fit on an MM ok? Wanted to get these for Winter. Perhaps RayJay will sell me his. :bows:..... I think you're referring to 16" steelie's??? They're on my car now and fit fine with my Blizzak's

Also since the MM is 03 and 04 there is no VSS or speedo gear to change correct? It's just programming. Yes that's correct..... You would have correct the speedo with the tune.
.................

[SC Cheesehead]

I can get a set of Gears installed for $260 cash, new crush sleeve and bearing kit etc. Very good technician.

I already have (i own it) a 3.73 (FRPP N gears) ring and pinon, plus I have a 28 spline traction lock with carbon fiber clutches (Reinhart)

The idea was that I'd have the 18" tires spinning at 3.73 ratio for summer and what not. Then put 17's on for winter and drags and such (which would make my effective RAR close to 4.10)

Anyone ever try a 3.90 gear set?

Also I find it hard to believe that the mileage went UP from 280 miles per tank with a 3.73 to 300 miles per tank with 4.10's

Do the 17" HD police steelies (which are cheap and tough) fit on an MM ok? Wanted to get these for Winter. Perhaps RayJay will sell me his. :bows:

Also since the MM is 03 and 04 there is no VSS or speedo gear to change correct? It's just programming.

Not so hard to believe when you consider that at 65-70 mph with 3.55 gears the engine is only running a bit over 2,000 rpm which is just outside the powerband. with 4.10s the engine is revving about 2,200 -2,400 which gets it up into the bottom of the power band, so the engine is actually running better.

I've tracked my mileage both before and after the gear swap, and impact on mileage is almost non-existent.

If you've got 3.73's fine, do the swap. As for 3.90's over 4.10's you're splitting hairs. As Bob (RFO) said in an earlier post, there's a bunch of us who have gone with 4.10's and know the resulting improvements.

If you feel compelled to ignore that advice and go off and try something else, have at it.:rolleyes:

[Vortech347]

Si senior Glenn.

my 03' had 3.73's.
This one has 4.10's.

4.10's ROCK all over 3.73's with EVERYTHING... The car feels MUCH lighter. You barely tap the gas and it pulls you up nicely.

Don't fear the gear!! Fear getting your ass kicked because you didn't have ENOUGH gear...

[juno]

3.73's do make a difference, but not the impact of 4.10's on an NA car. The 4.10's make it a lot more fun to drive, but as stated before, it's not a 200 rpm increase at highway speeds, it's 15%. In Florida, you can't drive 65-70 unless you are on 95 during rush hour. If your typical cruising higway speeds are closer to 75 to 80 or higher, you could see a 300 or better rpm increase. If you are keeping the car NA or considering a centri SC, 4.10's will be a lot of fun. I knew I was going the TC route almost from day 1, so I went with the 3.73's. 4.10's won't load the turbo quick enough. I can still put the speedo on the peg in 3rd. So when I nail it in 3rd at highway speeds by the time I get the wheels back straight I am at speedo peg and rpm limit and can decide if I want to click OD back on.

And yes, you will need to change gear size with your SCT to get your speedo correct. The predator cannot do that, you have to have a tuner do it, or you can approximate a tire size change to get close. (you can get close by changing tire size by the approximate gear size, ie increasing tire revs by 5%, 15% etc)

[mgmsleeper]

3.73's do make a difference, but not the impact of 4.10's on an NA car. The 4.10's make it a lot more fun to drive, but as stated before, it's not a 200 rpm increase at highway speeds, it's 15%. In Florida, you can't drive 65-70 unless you are on 95 during rush hour. If your typical cruising higway speeds are closer to 75 to 80 or higher, you could see a 300 or better rpm increase. If you are keeping the car NA or considering a centri SC, 4.10's will be a lot of fun. I knew I was going the TC route almost from day 1, so I went with the 3.73's. 4.10's won't load the turbo quick enough. I can still put the speedo on the peg in 3rd. So when I nail it in 3rd at highway speeds by the time I get the wheels back straight I am at speedo peg and rpm limit and can decide if I want to click OD back on.

And yes, you will need to change gear size with your SCT to get your speedo correct. The predator cannot do that, you have to have a tuner do it, or you can approximate a tire size change to get close. (you can get close by changing tire size by the approximate gear size, ie increasing tire revs by 5%, 15% etc)


:up: good info. im still undecided but i'll let dennis handle this thought.

[CKMustangCobra]

I want some opinions.

Taking torque curves, throttle position, fuel maps...... blah blah blah.

Does running an engine with the same load @ 2100rpms or 2400rpms acutally use more fuel?

[SC Cheesehead]

I want some opinions.

Taking torque curves, throttle position, fuel maps...... blah blah blah.

Does running an engine with the same load @ 2100rpms or 2400rpms acutally use more fuel?

Most guys report between 0 and 2 mpg difference after installing 4:10 gears. I've tracked my mileage before and after, and at highway speeds I've seen about 0.5 mpg difference but a whole heck of a lot better responsiveness. IMO, going to 4:10's is a no-brainer.

[offroadkarter]

:up: good info. im still undecided but i'll let dennis handle this thought.


Most 2v panther owners upgrade to 3.55 gears at the lowest, thats still a big jump from your 2.73's and you can get a used set from a MM cheap.

[1 Bad Merc]

Geeze.........most every guy on here has told you to go with the 4.10's! We have all experienced this and the majority of us have gone this route. You are not paying anymore for gas then we are and you will get the best of both worlds.

Now frickin' MAN-UP and get the 4.10's installed! Thanks for playing.