What rearend gear ratio?

[nearmiss]

The stock 3.45 rear end ratio seems really tall when coupled with the overdrive 5th and 6th gears. I have a daily driver C4 w/6 spd and was wondering if other people have changed this to something a little higher rev'ing and if there is any real downside?

Thanks for the advice, I need it!
nearmiss

 

[Tuna]

Lots of people use the 3.73 gear set and I've seen up to 4.11 use. It all depends on what you want out of your car. What are you looking to achieve?

Taller gears reduce gas mileage but increase acceleration (sometimes).

I'm still using the 3.45 in my car. It suits my driving requirements.

 

[nearmiss]

Thanks, Tuna. The car is a daily driver. Being a new Corvette owner, I'm not very familiar with the engine characteristics and it seems that I'm clocking around 2000 rpm somewhere close to 75 or 80 mph. At very common traffic type speeds 50-65 mph, it seems I'm in 5th alot. Do these motors enjoy running between 1k and 2k rpm?

 

[Black Bart]

Since your engine has a roller cam it should not run below 1400rpm for long periods of time or it won't get proper oiling.
Lot's of guy's run 411 gears but these usually make some noise and vibration they need to be setup right. The 411 gears would make first gear really low.
I have 3:30 rear gear and just use 5th for most two lane driving.
I have a supercharged and nitrous injected 455 cid small block so I like the 3:30 gear because it is hard to get traction with the 3:30 and lower gear would just result in more wheel spin.
Unless you are a serious drag racer I would leave the 3"45 gear in it and spend that money on something that would increase the power output.

 

[nearmiss]

Hi Black Bart, Thanks for the tip on staying above 1400 rpm for the roller cam. Getting down that low kindof feels like lugging the engine with it seeming to be "happier" above 2000.

 

[garycr14]

Gears

The 3.73 would seem like the logical choice, but I doubt that the difference from stock would be worth the investment. 4.11's will work great for racing, but might be a little too much if you use your car as a daily driver. Check out the post by Skant, he has just completed the mod on his LT4.

 

[Tuna]

Hi Black Bart, Thanks for the tip on staying above 1400 rpm for the roller cam. Getting down that low kindof feels like lugging the engine with it seeming to be "happier" above 2000.

As a previous LT4 owner (96 CE LT4 Z51) I understand where you are coming from. The LT4 just feels better above 2000.
Going with a 3.73 should make you feel better about using 6th on the highway but you can just as easily use 5th instead now. That's what I did. If you think you're going to need the power, you'll have to down shift anyway.
With the stock setup, 6th is just for gas mileage anyway and not worth much below 60MPH. In my 92 and 03, we rarely use 6th except for highway cruising anyway. The exception being gas mileage rallys. Then we use 6th down to about 45MPH - they get great mileage there but it feels awful!!!

 

[nearmiss]

Thanks Everyone. It looks like I get to save the costs of doing a differential gear swap out!

 

[garycr14]

Cost

Don't worry about saving the money, I'm sure we can figure out a way for you to spend it. $1500 will buy some decent horsepower.

 

[Skant]

As was mentioned, I've recently installed 4.11's in my LT4...

I'm dealing with some sound problems that may or may not have to do with them. But I'll tell you one thing...

I measured my acceleration with this new setup...

0-60mph in 4.3 seconds. Stock except for 4.11's, cold air intake, borla exhaust, coolant bypass, and hypertech power program.

And that's with relatively weak tires that are getting close to worn out. And not the best driver in the world wiggling the stick. My acceleration is very definately traction limitted.

I think you'd be hard pressed to develop that much acceleration via engine power enhancements for the price. In fact, I'm pretty sure that there is no cheaper way to do so.

Fuel mileage doesn't seem to have changed much. I was expecting more loss there.

- Skant

 

[Black Bart]

Don't worry about saving the money, I'm sure we can figure out a way for you to spend it. $1500 will buy some decent horsepower.

Yea 1500 would buy a killer NOS setup with money left over and a 3:45 gear with a 150 shot would just flat kick azz on a stock engine with 4:11 gear.

Since he said it is a daily driver the 4:11 would not be my choice.

 

[Skant]

My vette is my daily driver. I find the gear ratios with ZF6 + 4.11 to be quite fine for regular street driving. Typical freeway speeds still land between 1500-2100rpm. And you just don't use as much gas to get off the line when you start out from a stop. The harsh launch is always there at a moment's notice if you ask for it. But it's not hard to take off slow.

Fuel mileage around town doesn't change at all. Freeway gas mileage has dropped slightly, but not as much as I thought it would. I expected to lose at least 5 mpg on the freeway. In reality, it looks like I've lost maybe 2-3 mpg. Maybe even less.

My average fuel economy has dropped maybe 1-2 mpg. My driving habits put me maybe half and half city/freeway. And I've been a little heavier on the throttle lately since I've recently installed these toys.


I think the thing to realize is that the standard gearing in a ZF6 vette is _very_ tall... abnormally tall. 3.73 or 4.11 changes it from overly tall to approximately typical/normal (and really wakes up the car). 4.56 would be very aggressive, and would make it wind up a lot cruising on the freeway.

- Skant