Gears ??

[mojo92]

Now that I am new to the corvette group I just wanted to know.....are 3.73 gears good in a 4-speed auto L98. I have them in my 93 Cobra so they are a good low gear and you can really feel the power. If not what is???? The guy a got the vette from put as he said " highway gear " in WHAT IS HIGHWAY GEARS ?????? Anyway I don't know what gears are in it now but you really can't feel the low end with them, but top end is great.

 

[John Robinson]

Gear ratio's

GM had several gear ratio's available for the Corvette. Looking at the list of ratio's for my 93 there are 9 available from the factory. The standard ratio that was used for standard car orders was 2.59 this was the ratio that they used to pass emission and fuel regulations.

What does the gear ratio number mean? The lower the number (2.59) the lower the rpms are at cruising speed. The higher the number (3.54) the higher the engine rpms are at the same speed with the lower number axle. So the higher number does give you quicker acceleration from a start but what you gain there you lose at the top end, and you lose gas mileage.

On my 93 1000 RPM is about 44 MPH with my standard 2.59 ratio. Therefore at 75 MPH my engine is turning over at less than 2000RPM. Now before you start calculating 44 X 5000RPM and figuring top speed should be 220 MPH remember that the speed per 1000 RPM is in overdrive and in a flat out run for top end the car cannot pull that high a ratio so it reverts back to non overdrive high gear. Many other factors also come into play such as air drag etc. So if you have a higher gear ratio then you may be running something like 35 MPH at 1000 RPM (I did not calculate this I am only using it as an example) which means that theorectically you could go 175 at 5000 RPM. In reality you probably could not pull over 4300 RPM at top end which gives a top end about 150 MPH.

I hope this gives you a better understanding about what effect the gear ratio has on performance.

 

[jrzvette]

Now that I am new to the corvette group I just wanted to know.....are 3.73 gears good in a 4-speed auto L98. I have them in my 93 Cobra so they are a good low gear and you can really feel the power. If not what is???? The guy a got the vette from put as he said " highway gear " in WHAT IS HIGHWAY GEARS ?????? Anyway I don't know what gears are in it now but you really can't feel the low end with them, but top end is great.

On an automatic Corvette the standard rear was 2.59:1. The performance ratio (RPO G44) was 3.07:1. Both were the Dana 36 rears. Six speeds had a 3.54:1 ratio in a Dana 44.

While there are 30 or so ratios per this RPO list http://home.comcast.net/~igotoxs/GMRPOCodes.htm

they were not all offered on the Corvette in 1992.

Whether 3.73s will be good depends alot on the type of driving you do and your gas budget. Keep in mind that the lower ratios (higher numeric) multiply torque as well so if you're planning to spend a lot of time jumping on it from a dead stop make sure the rest of your drive train is up to the task.

 

[Hib Halverson]

First of all, if you have a 92 Coupe, you don't have the L98 engine, you have a more powerful unit known as the "LT1".

Rear axle gears in coupes of that vintage were either a 2.59 base ratio or 3.07 performance ratio.

3.73 is a very short gear for a C4 with an LT1. The first gear ratio in the 4L60 automatic is really low, 3.07. That in conjunction with a 3.73 axle means that, unless you put a serious tire under the car, all you're going to do is spin the tires.

With a stock or near stock 92, there's not much to ge gained with a 3.73 axle and stock tires.

In addition going from a 2.59 or a 3.07 to a 3.73 will mean a big gas mileage hit.

If you insist in a shorter axle ratio, I'd keep it to no more than 3.45 which was the ratio for many of the late 90s manual trans cars.

 

[Hib Halverson]

Ok. I misread the member information. You have a 91. Sorry.

Same holds true with 3.73s. With the 3.07 low gear in the 4L60, a set of 3.73s is going to spin the tires a lot and decrease fuel mileage. You can solve the tire spin problem by putting a wider tire under the back or, if you still want the different ratio, going to the 3.45.

 

[mojo92]

I just want a gear that will put you in your seat hard and that you will know that this car has alot of power. I know Ford and Chevy are not the same, but I have had alot of people ride in my Cobra and tell me that you can really feel the 3.73's pulling hard !! I want that in my vette to show the mustang guys that a vette is just as good or better.

 

[regalniz]

i put in 3.73's in my 94 lt1. it came with 3.07's. yes the tires do spin when launching but you will learn how to cope and feather the throttle. however, when they do hook, hold on. second gear hits and spins the tires again. be careful making half throttle lefts or rights. passing cars at freeway speeds is effortless. i would suggest not putting slicks in the rear. the dana 36 is the weak link. 315's at the most. mileage did suffer but you didnt buy a vette for the outstanding mpg's. if i had to do it again, i would still go with the 3.73's. i was afraid the 3.54's wouldn't make a difference. find a GOOD shop that is familier with this type of work. hope this helps. what year is your cobra? my brother has a 01 and i walk away from him every time. the 03's are the ones that give me a problem.

 

[jrzvette]

Ok. I misread the member information. You have a 91. Sorry.

Same holds true with 3.73s. With the 3.07 low gear in the 4L60, a set of 3.73s is going to spin the tires a lot and decrease fuel mileage. You can solve the tire spin problem by putting a wider tire under the back or, if you still want the different ratio, going to the 3.45.

Hib

I don't know if you misread or if the OP changed his information. After reading your first post I looked back and I'm certain he had listed his car as a 92 in his profile (or maybe it was his screen name that caused the confusion?) Or maybe we're both reaching "that age". :L

 

[John Robinson]

Hib

I don't know if you misread or if the OP changed his information. After reading your first post I looked back and I'm certain he had listed his car as a 92 in his profile (or maybe it was his screen name that caused the confusion?) Or maybe we're both reaching "that age". :L

I also thought it said 92 because as Hib said it was not an L98 if it was a 92.:confused

mojo92 How about looking under the console lid and copying down your RPO codes then let us know what they were. With them you can figure out exactly what the car had when it was built. There are many sites that list the RPO codes. Try this one www.corvetteactioncenter.com/tech/rpo/8496rpo.html

 

[regalniz]

i think we are all getting old. i had asked what year his cobra was and he clearly states he has a 93. wheres my ginko biloba?

 

[mojo92]

Ford has Ford Racing 3.73's, so what brand is best for the vettes? Will any 3.73's do or is there a brand I should get.

 

[regalniz]

i believe i bought mine from summit. there were richmond.

 

[Black Bart]

I have a 89 6 speed and it is powered with a supercharged nitrous oxide injected 406 and I use 3:73 gears.
With a stock engine and a decent tire you should not have that much of a traction problem.
Here is where I bought my gears http://www.tomsdifferentials.com/

 

[carguy604]

I've got 3.07's in my '92 with A/T and I believe that I've got the Dana 36 out back. I've been thinking of switching up to 3.54's but now I'm wondering if I'll notice much improvement in the bottom-end. I'm hesitant to go with 3.73's because I don't want my gas mileage to plummet too far down. Any suggestions? I do most of my driving in town.

 

[bart15]

I've got an 84 AT that I swapped the 3.07 for a 3.73. My highway mpg dropped from an average of 25-27 (the computer used to say 28mpg) to about 20-21 (with the computer telling me 23mpg).

In town I haven't noticed a huge difference in mpg. With the 3.07 it would usually hang in 3rd more anyway, now it will drop into 4th more... at the end of the day I'd say the in town mileage is about the same. But it's a lot more fun from the stoplights now.

 

[TedC]

The performance difference between the 2.59 and 3.07 is night and day. Like Hib stated above, higher ratios can cause traction issues. 1st to 2nd shift at WOT is wild on my stock 89 with 3.07, leaving twin patchs. I feel the 3.07 is the best balanced gear for an auto L98. Decent MPG, plenty of fun with stock tires, maintains good top speed, and is very responsive in daily driving. I did not like the 2.59 in my 1988 auto.

 

[MusclecarJohn]

I did not like the 2.59 in my 1988 auto.[/quote]
Hey Ted, I have 2.59s in my '92 LT1, do you think going to 3.07s will make much difference in an LT1? when accelerating from a stop, I don't really mind the 2.59s but I was thinking the 3.07s would be a better all around gearing for the LT1?

 

[TedC]

MusclecarJohn, This is a really a question for someone who has the LT1 engine and the G44 3.07 gear, but the LT1 produces peak HP and Torque higher up on the RPM scale than a L98 and you would expect this allows getting to that peak power quicker. I drove several LT1s with autos and the 2.59 gear and was very disappointed, especially in off-line get-up-and-go. I've read several articles that claim GM was forced to ship lots of C4 vettes with 2.59 gears to hit CAFE requirements. I can't find the post, but another CAC member explained why the 2.59 was not optimized for performance based on shift points and power curves.

 

[MusclecarJohn]

Thanks Ted, I'll do a search on the topic
now I'm second guessing my feeling about the 2.59s, I should probably go to a higher numeric gear ratio, but I'm not sure what I may get myself in to as far as the work to be done:ugh

 

[reoch999]

Thanks Ted, I'll do a search on the topic
now I'm second guessing my feeling about the 2.59s, I should probably go to a higher numeric gear ratio, but I'm not sure what I may get myself in to as far as the work to be done:ugh

Unless you're a very capable mechanic with experience aligning parts to the .005 inch, a gear swap in a street car is best left to the professionals. That said, I have a 3.75 ring & pinion set waiting to go into my 92. My first "toy" car was a 91 Camaro and going from a 2.73 to a 3.42 helped a ton, and really didn't make a big difference in gas mileage. I'm excited to see what the vette will do, going from 3.07 to 3.75.