3.73 Or 3.90

whitesnake1994 · Aug 8, 2005

To those of you who have 3.73s do you regret not getting 3.90 or even 4.10s? Also what would be the difference in RPMs at about 80 mph between the three gears? Also i am not planning on putting a power adder on if that makes a difference, so what do you reccomend for me? Thanks

Kevin R. · Aug 8, 2005

I have 3.73's and an automatic, so my rpm's at 80 would be around 3500-4000. It kind of sucks for highway driving and since I kind of have a heavy foot I am glad sometimes I don't have a higher gear.

But then again taking off from stop lights I wish I had 4.10's.

88GT460 · Aug 8, 2005

3.90 are a great gear. I got 4.30's though.

final5-0 · Aug 8, 2005

There are quite a few programs around that let you plug in the value of your tire size, mph, ratio, etc. to see how various things in your drive train effect each other.

Don't have any of those links on this pc but search around and you can find them.

Later
Grady

Touring23 · Aug 8, 2005

This is from my spreadsheet, condensed table for cruise, for use with 255/45.17 and 5spd (can someone double-check my math please):

mph 3.08 3.55 3.73 3.90 4.10
35 1865 2149 1685 1762 1852
45 1789 2062 2167 2266 2382
70 1892 2181 2292 2396 2519
80 2163 2493 2619 2738 2879
100 2704 3116 3274 3423 3599

Yes, I wish I had gone to 3.90; 3.73 is much better than 3.08, but it wasn't enough for me. But then again, it's not the DD and my only interest in mileage is for tuning and maintenance.
To make a recommendation, we need more info about the car (vert? big wheels?) and it's usage (track warrior? Trailer queen? Daily interstate commuter?)

MysteryMachine · Aug 8, 2005

good question. my dad keeps telling me i should go with 4.10s (old muscle car guy) but everybody tells me 3.73's it will be nice to know what you guys have to say about this.

94-302-vert · Aug 8, 2005

I am happy with my 3.73's and manual trans. There are days I want to jsut clip along on the highway and I wish I had 3.55's but there hasn't been a day yet that I wished I went with 3.90's or 4.10's. At 134k miles my motor doesn't need that revving.

Now on the other hand I haven't taken it to the track yet either, maybe if I did that more oftern I would want 4.10's.

mootang · Aug 8, 2005

i honestly wish that i went with 4.10's instead of 3.73's. they put you in a better power band when you cross the finish line in the 1/4.

i think the gain in performance would be worth the slight loss in drivability.

pleasehelp · Aug 8, 2005

Here is a Speed/RPM calculator link: http://www.car-videos.com/tools/spe...o7=&Redline=6250&Increment=500&B1=Recalculate

It is already setup for 3.90 rear end gear and 315/35/17 size rear wheel. But you can plug in any combo you want to find out speed and rpm.

whitesnake1994 · Aug 8, 2005

i have 94 cobra coupe and it is my daily driver. it has 94000 miles on it. L/T headers, O/R H, and flowmaster A/T catback. underdrive pullies and a drop in k&n.
also how much worse is the gas milege b/t 3.73 and 3.90, i do a bit of highway driving and usually drive around 80. Thanks Again

final5-0 · Aug 8, 2005

Here is one that has mph included

http://www.allfordmustangs.com/Detailed/608.shtml

Later
Grady

MarkFJ40 · Aug 8, 2005

I've got 3.73's and I am just hitting 4th at the end of the 1/4 mile and I wish I had 4.10's.

18mustangs · Aug 8, 2005

94-302-vert said:
I am happy with my 3.73's and manual trans. There are days I want to jsut clip along on the highway and I wish I had 3.55's but there hasn't been a day yet that I wished I went with 3.90's or 4.10's. At 134k miles my motor doesn't need that revving.

Now on the other hand I haven't taken it to the track yet either, maybe if I did that more oftern I would want 4.10's.

I used to think about upgrading to 4.10s from my 3.73s, but I've got enough traction issues already! honestly 3.73s are great all around, not bad on the highway and good in town.

mackey · Aug 8, 2005

All motor 4.10
Power Added: 3:73

Best is in the middle if you can't decide. 3:90

Touring23 · Aug 8, 2005

final5-0 said:
Here is one that has mph included

http://www.allfordmustangs.com/Detailed/608.shtml

Later
Grady

That's a nice calculator. Good find. It agrees with my calculations, FWIW.

also how much worse is the gas milege b/t 3.73 and 3.90, i do a bit of highway driving and usually drive around 80. Thanks Again

Statistically I haven't seen much change from 3.08 to 3.73, approximately 0.2mpg, and that's a big change in gearing; I'll be really surprised if you can measure a difference in mileage between the 3.73 and the 3.90, they're so close. Either one should do the trick.

Grn92LX · Aug 8, 2005

Kevin R. said:
I have 3.73's and an automatic, so my rpm's at 80 would be around 3500-4000. It kind of sucks for highway driving and since I kind of have a heavy foot I am glad sometimes I don't have a higher gear.

On what planet does a 3.73 geared automatic AODE car run 3500-4000 rpm on the highway @ 80 You'd either had to forgot to put it in OD or have a C4 transmission. My friends AOD 4.10 geared car does 2500 rpm at around 70ish.

In general the best overall gear for the typical person is a 3.73 for a 5spd car and 4.10 for an automatic. This is just in general. I know with my car the best gear would be a 4.30, but I think a 4.10 is what i'll do down the road to replace my too tiny 3.73's that make noise.

final5-0 · Aug 8, 2005

Touring23 said:
That's a nice calculator. Good find. It agrees with my calculations, FWIW.

Statistically I haven't seen much change from 3.08 to 3.73, approximately 0.2mpg, and that's a big change in gearing; I'll be really surprised if you can measure a difference in mileage between the 3.73 and the 3.90, they're so close. Either one should do the trick.

You are so right on the money about ratios that are really close. For a street driven car, those close to each other ratios are a toss up so go with the higher number for a bit more zip. It just ain't gonna use any more gas or turn any more rpm.

A good rule of thumb...you gota go at least 1/2 a turn to tell any difference.

Lots of peeps fret way too much with gear ratios. Just a little math would ease their mind and that math deals in the facts, not opinions.

Later
Grady

mo_dingo · Aug 8, 2005

mootang said:
i honestly wish that i went with 4.10's instead of 3.73's. they put you in a better power band when you cross the finish line in the 1/4.

i think the gain in performance would be worth the slight loss in drivability.

Ditto that...regret sucks.

Just means I need more power.....muuaahhhahahahha.
Scott

Nobody · Aug 8, 2005

If you run the stock tire height and plan on trapping faster than 108 then you won't want 4.10's. You will run out of RPM. If you don't care about the drag strip or you are trapping well below 108, then get 4.10's.

mackey · Aug 9, 2005

Nobody said:
If you run the stock tire height and plan on trapping faster than 108 then you won't want 4.10's. You will run out of RPM. If you don't care about the drag strip or you are trapping well below 108, then get 4.10's.

That really matters what combo you are running. With the stock H/C/I you will not make power past 5500. If you have a higher revving setup. Lets say your car makes power to 6500 then the 4.10s will be ideal or you might need a steeper gear.

3.73 Or 3.90

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