how short will first gear be??

Foxfan88

My Grandpa has great wood.

Sep 13, 2004

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Miami, Ok

Oct 8, 2005

#1

• Oct 8, 2005

• #1

ok i am wondering how much 3.90s will affect my gears...

right now with my 2.73s
1st will stretch to about 45
second will hit about 70

what can i expect with 3.90s

will it cut 1st down so much it wont be fun??

 

8

87gtconv

ragtopman

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Feb 11, 1999

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Oct 8, 2005

#2

• Oct 8, 2005

• #2

With 3.73 rears and a t5 stock box I could not get half way through an intersection without shifting. 60 mph at 5th gear was like 3000 rpm's. My solution was to put a 2.95 gear set in my T5. Stil workingon it but it should gie me a usefull 1st gear and less rpm's on the highway. Love my 3.73 gear though for my heavier vert it is perfect for getting off the line on street tires.

 

T

Topdowncruise

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Apr 7, 2005

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#3

• Oct 8, 2005

• #3

I switched out the stock 2.73's last spring.The 2.73's make the car very easy and relaxing to drive but not as sporty and acceleration is mediocre.You will definately find first gear shorter and you will be working your shifter a lot more in town with 3.90's.I am glad I didn't listen to the Don't fear the Gear types who will recommend you go to 4.10's. The 3.55's are lots for the kind of driving I do and I think are well matched to my mods.In the end it depends on your own type of driving.

 

Michael Yount

Mustang Master

Apr 10, 2002

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Charlotte, NC

Oct 8, 2005

#4

• Oct 8, 2005

• #4

It's simple math to figure the impact of the gear change. At any given road speed, 3.90's from 2.73's will increase your engine rpm by this ratio -- 3.90/2.73 = 1.43, or 43%. Conversely, at the same rpm (redline) your road speed will be decreased by the same amount. So if it goes to 45 mph in first now, with 3.90's it'll be done with first at about 32 mph; if it's good for 70 in second, w/3.90's second will be good for about 49 mph. If your cruise rpm at 70 mph in 5th is 1700 rpm now, it'll be about 2450 rpm with the 3.90's.

My car has 3.73's, but I run a bit shorter tire than the Stangs, so it revs like a Stang with 3.90's. I like that gearing. I also have a T5Z tranny with a longer first gear (2.95 instead of 3.35) and a longer 5th gear (.625 instead of .675). So first gear isn't quite so short, and my 70 mph cruise speed is about 2300 rpm. It's pretty easy for me to start out in 2nd gear...

 

notchback

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May 30, 2000

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St Clair Shores MI

Oct 8, 2005

#5

• Oct 8, 2005

• #5

Foxfan88 said:

will it cut 1st down so much it wont be fun??

Click to expand...

go w/ 4.10's and it really be fun

a stock everything 5-speed on 4.10's and slicks can get a 6" wheel lift

i like 4.10's...short gears , but runs like a raped ape

i hate driving my car w/ 2.73's

can't wait for the 4.10 install

 

T

Topdowncruise

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#6

• Oct 8, 2005

• #6

87gtconv said:

With 3.73 rears and a t5 stock box I could not get half way through an intersection without shifting. 60 mph at 5th gear was like 3000 rpm's. My solution was to put a 2.95 gear set in my T5. Stil workingon it but it should gie me a usefull 1st gear and less rpm's on the highway. Love my 3.73 gear though for my heavier vert it is perfect for getting off the line on street tires.

Click to expand...

I don't think changing your first will result in less rpm's on the highway.Wouldn't you have to change the 5th gear?

 

Euphoric306

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Apr 5, 2004

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Oct 8, 2005

#7

• Oct 8, 2005

• #7

keep in mind guys he's going from 2.73 auto to 3.90 stick, i dunno wut ratios the aod has but i would imagine they're different?

 

Foxfan88

My Grandpa has great wood.

Sep 13, 2004

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Miami, Ok

Oct 8, 2005

#8

• Oct 8, 2005

• #8

yeah i forgot to add that
i believe the t5 is much steeper in gear ratios

 

dstanggt50

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Oct 8, 2005

#9

• Oct 8, 2005

• #9

I've had 4.10's in my auto 87gt, and in my 95 now, Its not bad for gas milage, I would assume it would be close to what 3.73 would be, I would recommend them, althought, if I'm gettin on the throttle, because of traction, I shift into second sometimes before I cross an intersection, but w/some traction it wouldn't be so bad. (5 spd)

 

Michael Yount

Mustang Master

Apr 10, 2002

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Charlotte, NC

Oct 8, 2005

#10

• Oct 8, 2005

• #10

topdown was referring to the first gear change in regard to making it across the intersection without having to shift....not cruise rpms.

 

notchback

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#11

• Oct 8, 2005

• #11

aod 1st gear = 2.40
t5 = 3.35

aod 2nd = 1.47
t5= 1.93

aod 3rd= 1.0
t5= 1.29

aod 4th = .068 (might be .069)
t5= 1.0

t5 5th = .068

aode and wide gear set from motorsport makes 1st 2.84 and 2nd 1.55

 

The Fox

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Mar 30, 2005

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Port Elizabeth

Oct 8, 2005

#12

• Oct 8, 2005

• #12

what about a 4cyl T5 and 3.73s? I think the first gear in in is 3.90? So what would my first gear top out at? 30mph? I need a TKO600 NOW...

 

Michael Yount

Mustang Master

Apr 10, 2002

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Charlotte, NC

Oct 8, 2005

#13

• Oct 8, 2005

• #13

Do the math -- we show'd you how.....

Hint - it would be LESS than 30....

You have to be careful about comparing gear ratios between automatics and manuals -- because of the torque converter and slippage the automatic will 'act' like it has a bit more gear than the ratio would make you think.

 

fox racer

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Jun 22, 2004

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Staten Island, NYC

Oct 8, 2005

#14

• Oct 8, 2005

• #14

the 2.95 first gear is great. i have 3.55's and a T5Z (2.95 first gear) and i get to like 35 in first (im guessin never really checked it specifically)

 

maverick0716

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Jan 12, 2002

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Oct 8, 2005

#15

• Oct 8, 2005

• #15

87gtconv said:

With 3.73 rears and a t5 stock box I could not get half way through an intersection without shifting. 60 mph at 5th gear was like 3000 rpm's. My solution was to put a 2.95 gear set in my T5. Stil workingon it but it should gie me a usefull 1st gear and less rpm's on the highway. Love my 3.73 gear though for my heavier vert it is perfect for getting off the line on street tires.

Click to expand...

I think you mean 2000 rpms at 60 mph, not 3000.

 

8

87gtconv

ragtopman

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Oct 8, 2005

#16

• Oct 8, 2005

• #16

maverick0716 said:

I think you mean 2000 rpms at 60 mph, not 3000.

Click to expand...

NO it reads 3000 rpm's maybe it has the wrong speedo gear but it reads 3000 rpm's at 60 mph! Lets back up, I think it read 3000 rpms's at 70 ph where it use to read arount 2000 rpm's! That sounds right dont it?? Nobody goes 60 mph on the freeways here I would have been run over!!


Also, I am not sure why but the tranny shop where I bought the parts swears to me that fifth gear will be 62.5% overdrive as oposed to now wich is 68%. Why, I dont know cause they still use the same fifth gear and fourth stays at 1:1. Anyone know?? Was I sold a bill of bad goods??? It does use a different cluter shaft and input shaft so is that were the change in ratio is made?????. G force as a 59% overdrive but there gears are much more expensive.

 

maverick0716

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Oct 8, 2005

#17

• Oct 8, 2005

• #17

Your transmission gears don't change....only your rear end (differential) gears. Unless you put in a different transmission, then you have a 0.68 5th gear.

 

Michael Yount

Mustang Master

Apr 10, 2002

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Charlotte, NC

Oct 8, 2005

#18

• Oct 8, 2005

• #18

87gtconv - sounds like something is way off. With 3.73's at 70 mph your rpm should be around 2400-2500 with the standard T5 5th gear (.675). If you had a T5Z -- then you'd have a .625 5th, and rpm would be around 2300 at 70. At 60 you should be down around 2000. So either your tach or speedo is quite a bit off.

T5 -- 3.35, 1.94, 1.29, 1.00, .675
T5Z --2.95, 1.94, 1.34, 1.00, .625

 

8

87gtconv

ragtopman

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Feb 11, 1999

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Oct 17, 2005

#19

• Oct 17, 2005

• #19

Michael, with the new tranny and the 2.95 first gear and .625 5th gear it is now registering about (stock tach is not well indexed) 2600 rpms at 80 mph. Does that sound better? I am running 245/45/16 tires but I did have my new Mororsports 140 mph speedo calibrated with that tire/wheel combo and I was off about 1 mph from 60 thru 80 mph. Have not rechecked everything after I put in the new rear gears but I did go to the red speedo gear. Visual evidence tells me that 80 mph seems to be close to an accurate speed.

 

M

meangreen92lx

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May 24, 2004

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Milwaukee, Wisconsin

Oct 17, 2005

#20

• Oct 17, 2005

• #20

I was a little worried about replacing my 3.55's with 4.10's but now that I have, I would never go back. At least with the current combo that is. The 3.55's are great on the x-way . I needed a steeper gear with my cam choice and couldn't be happier now. It pulls alot harder and gets in it's powerband quciker now. I can't even imagine running 2.73's....