2:73 VS 3:73 ratio

[FoxJosh]

Hey guys! My ‘90 vert is 100% stock with the 2:73 gears. I have a 3:73 set, but I do a lot of Highway driving. The acceleration kind of sucks with the stock gear especially with a stock engine set up. It does get decent fuel mileage and the engine runs 1200 rpm at 67 mph. Do y’all think it would be to my advantage to install the 3:73 or is it too much for the highway? Thanks in advance

[AldeanFan]

I’d go for it if you’ve got them.
I have 355s and have lots left on the highway.

Find an rpm calculator online and you can enter your tire size, rearend gear and overdrive gear and it will tell you your rpm



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[Ourobos]

Manual - 3.73s.

Auto - 4.10s

[gr79]

67 mph w/3.73 is approx 1650 rpm in this case

http://www.4lo.com/4LoCalc.htm
'find rpm' calculator
plug in 67, 2.73, .49 trans, t case 1, 25" tires= 1200 rpm
then change 2.73 to 3.73

[86MustangGtRob]

When I had my 86 gt with the 3.08 gears. I was turning around 1600 rpms at 63 miles an hour. That calculation seems a little off.

[homer302]

Manual - 3.73s.

Auto - 4.10s

This^^^^^^ I have one with 3:08s, one with 3:55s, and one with 3:73s if you want to come drive them. All 5 speeds. Not sure where you live.

[homer302]

GRRR.....Are you sure you want to leave this page??????? double post for the FAIL.

[FoxJosh]

Thank you

[FoxJosh]

Man, that’s an awesome offer, gee thanks. I live in NC.

[gr79]

ball park figures
assumed 25" tire
Gt is prob 26"
Had to use .5 od ratio w/26" to get the calculator to match the numbers posted.
pretty low number for od ratio
63/3.08/1600/26" matched closer with .6 trans od ratio.
are these auto or manual trans?
od ratios should be .60's to low .80's

[Broncojunkie]

I like my t5 with 3.73, but I have to admit... the 3.55 I had before it was such a well-rounded gear for a cruiser. I only really miss it when I'm on the highway for extended periods. The 3.73 isn't horrible, but I feel like I need to keep speeds down to be nice to the engine.

[Haystack]

I went to 28" tires to drop my rpms on one if my cars. 2.73 gear with and aod and .67 od was about 1600 rpms at 80mph. Could squeeze 30+ mpg on long road trips. Actually got almost 34 on a 600 mile tank of gas, all freeway

[sm41]

Where in NC? I'm in Jacksonville, and go to Wilmington almost every weekend. I've got 3.73s if you want to give it a try.
I really like the 3.73s as a street gear. Highway rpms still aren't very high, and even with the GT40P heads and intake it hauls down about 23 mpg. Lot more fun around town too! Tires beware

[FoxJosh]

I’m in Hickory area, kind of at the “foothills.”

[sm41]

That's a bit far, but if you find yourself down at the beach, just let me know

[cb650]

I like my t5 with 3.73, but I have to admit... the 3.55 I had before it was such a well-rounded gear for a cruiser. I only really miss it when I'm on the highway for extended periods. The 3.73 isn't horrible, but I feel like I need to keep speeds down to be nice to the engine.

This would be my opinion. I have 373s but on hiway seems to keep engine buzzing. I dont do much hi way anyway. And to keep up with traffic is worse. 2300 at 70 ish.
I have t-5 and 255/60 15 rears. If I did a lot of hiway would go 308 or 343 no more.

[cb650]

Opps LOL

[emerygt350]

Since tires make such a big difference on that ratio, personally, I would go low (short) on the gears and then do tire adjustment to get it where you want it for whatever application. I like the 3.73s way way more than the 3.27 i had stock with my AOD for street driving but for racing I am moving to much lower profile tires now. That way I get 2.1k rpm at 65mph driving daily and on the track I will have something in the range of a 4.21 ratio.
In this case it is going from a 225/60r15 to a 225/45r15 (stock 15x7 wheels, or trust me, I would go wider). A move from a 25.6 inch diameter to 23 inch or so.

A nice website to play with these formulas can be found here: http://www.kabamus.com/garage/gears.html#gearspeeddata

It is also nice to compare to your dyno chart to figure out how to stay in the peak areas of the curve.

[homer302]

^^^This is an idea but personally (maybe I am OCD). Wait, probably I am OCD. A certain vehicle with a certain ride height need exactly this size tire. Whatever "THIS" is depends on the car and ride height and fenderwell clearance. It just looks weird if the sidewall is too high or short etc. Most people put like a 245 series tires on a 7 inch rim which just ruins the handling. Does it hold air? Sure it does. But the car handles so much worse than it would with proper size tires. But if your goal is to dial in the RPMs this would be one way to do it.

[homer302]

I’m in Hickory area, kind of at the “foothills.”

I'm in Charlotte. Come down to AutoFair this weekend. Do a search on the event.

[burntorange84]

I like the 3.27 ratio in my 5 sp. I think it is the best overall. I can place it in 5th @ 45mph if just cruising and still get good hard acceleration when called on. I believe I'm just shy of 2k at 70mph. This of course will be a personal preference. If you do a lot of highway, I think the 3.73's are too high. Acceleration wise, the 3.73's will be awesome. For performance, most 5sp's went with 3.55 & autos with 3.73's.

in any regard, change the 2.73's!

-j

[78futura]

I am going to run 3.31 gears on my car cause it is a c4. I hope I can spin the tires maybe? I sure cant with 300rwhp and a 2.64 open end 7.5.. it leaves like a golf cart and at 30mph takes off with no wheelspin... my stock 140 crank horse 79 would light up both with a 3.08 8.8.
If I had a t5 would probably go 3.55.

[Str8sixfan]

I am going to run 3.31 gears on my car cause it is a c4. I hope I can spin the tires maybe? I sure cant with 300rwhp and a 2.64 open end 7.5.. it leaves like a golf cart and at 30mph takes off with no wheelspin... my stock 140 crank horse 79 would light up both with a 3.08 8.8.
If I had a t5 would probably go 3.55.

Ha! 78...I'm doing 3.27s for the same reason, but I don't think I'll scratch 300hp.

[emerygt350]

not saying a 225/45 isn't gonna be ugly (not 245), but that 4.21 is for racing, not highway and for people to look at. Apparently I just bought the loudest autocross tires on earth so there is no way I am cruising with them anyway.

[86FOX4EYE]

I like the 3.27 ratio in my 5 sp. I think it is the best overall. I can place it in 5th @ 45mph if just cruising and still get good hard acceleration when called on. I believe I'm just shy of 2k at 70mph. This of course will be a personal preference. If you do a lot of highway, I think the 3.73's are too high. Acceleration wise, the 3.73's will be awesome. For performance, most 5sp's went with 3.55 & autos with 3.73's.

in any regard, change the 2.73's!

-j

I have been through a lot of gear changes. My best well rounded street set up for a stock 225/60 15 tire is a 3.27 R&P with a 2.95 first and a .80 5th. 1st gets me all the way through the intersection and all gears through 5th are power on tap. Car rarely falls below 2000 rpm and 5th is a totally usable integration. Runs about 2500 rpm @ 70mph on the freeway. Just my 2 cents.