Time differences between gear sets: 3.55 vs 3.73

johnny_munyak · May 3, 2010

94/95 GTs have a very deep 1st gear which makes it pretty much useless with anything over 3.73.

I have 3.55s in my car and like them alot. They are an excellent street/highway gear - huge improvement over the stock 2.73s.

I keep hearing that you are leaving some performance on the table using 3.55 instead of 3.73s and that the ETs for 3.73 will be better........BUT noone ever verifies by how much? Is it 1 tenth? 2 tenths?? The average street driver would not even notice 1 or 2 tenths.

Just trying to justify the cost of a gear swap....?

My gut feeling tells me that the time differences between them would be negligible and that the 3.55s also have their advantages over the 3.73s depending on where or how they drive their cars.

Any input is welcomed.....

KamiKaziDK · May 3, 2010

don't waste your money, keep the 3.55s, they're perfect for a T5

393strokervert · May 3, 2010

KamiKaziDK said:
don't waste your money, keep the 3.55s, they're perfect for a T5

+1

Adam95GT · May 3, 2010

Get 4.10's ...

final5-0 · May 3, 2010

It simply boils down to this

There is not much difference between the two ...

I mean the .08 difference is less than a tenth :Word:

Now .. if one had the OEM 273's or 308's then I would tell them to
pick the steeper ratio

but

To change 355's to 373's would be a waste of money to me when
talking about a street car application

About the short 1st gear

Yes ... if talking about the OEM power band it will be short
but
If you got h/c/i which extends the power band ... it becomes longer

Grady

johnny_munyak · May 3, 2010

Yes, I have some goodies done. H/C/I, exhaust, pulleys, etc, etc. Guessing somewhere between 300-350 FWHP. With the headwork done, I was told the valvetrain would handle 7500 RPM.....but stock bottom end around 6500 RPM, and cam drops off at about 5500 RPM.

I went with 3.55s since the car is a freeway/highway cruiser. Doubt it will ever see a track, but you never know? =0)

A guy just hates hearing he is leaving something on the table......I just can't see by going to 3.73 that they would be a huge gain.

COBRA90GT · May 3, 2010

johnny_munyak said:
...I went with 3.55s since the car is a freeway/highway cruiser...

Sounds about right to me then.

BlackVert · May 4, 2010

johnny_munyak said:
Yes, I have some goodies done. H/C/I, exhaust, pulleys, etc, etc. Guessing somewhere between 300-350 FWHP. With the headwork done, I was told the valvetrain would handle 7500 RPM.....but stock bottom end around 6500 RPM, and cam drops off at about 5500 RPM.

I went with 3.55s since the car is a freeway/highway cruiser. Doubt it will ever see a track, but you never know? =0)

A guy just hates hearing he is leaving something on the table......I just can't see by going to 3.73 that they would be a huge gain.

mine is also a cruiser that will not likely to ever see the track ... let me ask you a couple questions ...

(1) how close to reality is your speedo now with the 3.55s? i have 3.27s now and am considering changing gears to something steeper, but when i had 3.73s and 4.10s, the speedo (and odometer) was never accurate, and it really bothered me. if the speedo gear (you know what i mean, the one in the back of the tranny) actually makes the speedo/odometer correct, then 3.55s might be a good choice for me.

(2) what rpm are you seeing at 70mph on the highway?

and no, adam, i won't be going to 4.10s!

johnny_munyak · May 4, 2010

My speedo is quite accurate as measured by a pilot vehicle that was following me. I put a 23 tooth white speedo gear to compensate for the gear change. According to my tach, 60 MPH yields around 2000 RPM. 70-75 MPH is around 2400 RPM. Downshifting to 4th at 70-75 MPH yields a spike of RPM to around 3500-3600ish (which is a nice spot on the cam) and pulls away pretty hard.

Driving around the city, I"m usually in 3rd gear. It really seems to work quite well.

Last5.0 · May 4, 2010

I've had 3.55's in mine since '96 and have loved them. I have cut a best 60' at the track of 1.62. A few years ago I installed a TKO600 with the 2.87 first gear (instead of the 3.35 like the t5) and I don't like it as much and have not gotten near that time even with more power. I'm wanting 3.73's now but can't justify the cost for that little of difference.

Another thing to think about is what rpm in 4th gear you will be going through the traps at. If you have too steep a gear and not enough engine mods/power you will be bouncing off the limiter at the end of the track....or shifting into 5th...lol

johnny_munyak · May 4, 2010

Thank you for mentioning that......that is precisely the other reason I chose to go with 3.55's. With a stock engine, 3.73 will be reving pretty tight by the time you hit the end of the track. 3.55's will allow a couple hundred RPMs of breathing room before having to shift into 5th (overdrive).

final5-0 · May 6, 2010

johnny_munyak said:
I went with 3.55s since the car is a freeway/highway cruiser. Doubt it will ever see a track, but you never know? =0)

This is one of those things that has been said over and over

If you do the math hard data dispels opinions

You will find that that statement is one of those things that is not as
it first appears to be

It usually works out to be only about 125 more rpm with the 373's

Grady

lehrskee · May 6, 2010

not to hijack your thread but i have a question that goes with the subject. im getting gears but i dont know whether to get 4.10 or 3.73s.right now i have stock 3.27s i think. im not really worried about mpg. my questions are how much faster will i run at the track going to the 3.73s or with the 4.10s. i want the most power/acceleration possible. second question is how much top end will i lose with 4.10s over 3.73s. im leaning towards the 4.10s. any input will help. sorry again for hijacking.

johnny_munyak · May 7, 2010

final5-0 said:
It usually works out to be only about 125 more rpm with the 373's

Grady

So them how much more performance can be acquired by going from 3.55s to 3.73s?

I doubt its much if any....

final5-0 · May 8, 2010

johnny_munyak said:
So them how much more performance can be acquired by going from 3.55s to 3.73s?

I doubt its much if any....

This is the whole point of our discussion here :Word:

There IS NOT much difference between the two ratios

B U T

If one was gonna go from stock to a steeper ratio

Don't be afraid to do the steeper ratio with concerns of highway rpm's

Don't buy into the myth

You are gonna save a bunch of rpm crusing down
the highway with the 355's

Grady

moneypit94 · May 8, 2010

As far as running out of RPMS at the end of the track you shouldn't worry about it. I was talking to the guys at AFM about that awhile back and i remember them talking about how in moderation that they have gotten their costomers considerably faster with bigger gears and the customers said they were right on the rev limiter at the end of the 1/4 previously. If i remember right their mph raised too which kinda surprised me.

Now I had one racer explain to me that you actually get less tire slip with larger gears, and his explanation was that yes they may break free a bit easier but when then do the tire speed isn't as quick so it can catch up easier. Not sure how much i buy into that but it does make some sense.

So if you follow that logic then the faster you hook up the more power thats put to the ground which means the more distance you can cover which probably averages out.

Plus racing is all about the first 60'. Thats why these big ass torque monster chevy cars that actually don't have all that much hp run 10's so easily and their mph seems really low. They have all their torque to get them off the line and and nothing left to push them at the end. Also why you see these top fuel cars blow up in the first 60 feet and coast the rest of the way down the trach to an 8 sec run at 78 mph.

But between 3.55's and 3.73's i wouldn't waste your time if it was me. But 4.10's on the other hand I would consider. Even though i say that im running a whopping 3.25's in mine in mine right now. lol

final5-0 · May 8, 2010

moneypit94 said:
Now I had one racer explain to me that you actually get less tire slip with larger gears, and his explanation was that yes they may break free a bit easier but when then do the tire speed isn't as quick so it can catch up easier. Not sure how much i buy into that but it does make some sense.

This is something not many folk think about but it is true

Have you ever broke the tires loose in second gear at low speed when it is raining?

Notice how you have to back ALL THE WAY off the pedal to gain control

You do the same in first gear and a lot of the time ..........
You gain control with just a reduction of pedal

Grady

302GTS · May 8, 2010

final5-0 said:
This is something not many folk think about but it is true

Have you ever broke the tires loose in second gear at low speed when it is raining?

Notice how you have to back ALL THE WAY off the pedal to gain control

You do the same in first gear and a lot of the time ..........
You gain control with just a reduction of pedal

Grady

So very true. First gear is REALLY easy to moderate tire spin with, even with my stock 2.73 gear out back. Second, on the other hand, will sit at 4,000 rpms just smoking down the street.

lehrskee · May 8, 2010

i am going to be buying gears really soon. probably 4.10's. now ive read that jus changing the speedo gear wont make it accurate, that ill have to change something inside the transmission also. is this true.

final5-0 · May 9, 2010

Yes that is true

You can't just change the driven gear

You gotta change the drive gear in the tailshaft of the trans

Do a search on here

It has been talked about many times with all the details

You can also do the speed cal thing as well

Grady

Time differences between gear sets: 3.55 vs 3.73

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