Choosing The Right Gear Ratios

[INSOMNIAC]

I need some help to choose the right gear ratios for my car.
Can somebody plug in the following data and give me the top speed in every gear for each gear ratio?

Axle Ratio : Stock 3.07
Rear Tire Size : 345/30 – 18 (1 inch shorter than stock tire)

Gear Ratio Set 1
1st Gear – 2.62
2nd Gear – 1.73
3rd Gear – 1.35
4th Gear – 1.00
5Th Gear – 0.83
6th Gear – 0.73
Alternative 1
5th Gear – 0.86
6th Gear – 0.73
Alternative 2
5th Gear – 0.74 (Stock gear ratio)
6th Gear – 0.50 (Stock gear ratio)


Gear Ratio Set 2
1st Gear – 2.71
2nd Gear – 1.79
3rd Gear – 1.30
4th Gear – 1.00
5Th Gear – 0.86
6th Gear – 0.75
Alternative 1
5th Gear – 0.89
6th Gear – 0.75
Alternative 2
5th Gear – 0.74 (Stock gear ratio)
6th Gear – 0.50 (Stock gear ratio)

Thanks.

 

[Kai SRT10]

Go here:


http://www.5speedtransmissions.com/calculators.html


I'm one of the few who likes the stock ratios for 1st through 4th gear.
For road courses, the tall gears work perfectly, I think.

However, I've looked long and hard at changing the 5th and 6th gear ratios to make the car a true 6 speed. I've found that the car bogs pretty bad when shifting hard from the top of 4th into 5th.

Here is what I would consider the ideal set up. 1-4 are stock, the current 5th gear becomes 6th gear, and a new .84 fifth gear is added (.84 gear is used on the Corvette tremec t.56)

Modified Viper T56 (2.66, 1.78, 1.3, 1.00, 0.84, 0.74)

Speed at 6000 rpm with stock tires is:

58; 89; 121; 158; 188; 213

With all the engine modifications I'm doing, I'm going to wait and see if the car still bogs when shifting into 5th. The extra hp and tq may have solved my issue. If not, then a 5th and 6th gear change-out is likely in my car's future.

Kai

 

[INSOMNIAC]

Go here:


http://www.5speedtransmissions.com/calculators.html

Perfect. http://www.5speedtransmissions.com/gear_calculator.html

Thank you.

 

[Vipermann]

I have a 3.45 rear gear ... How difficult is it if I wanted to just change 3rd gear to a slight lower ratio (like a 1.23, as in the Ford GT)?

 

[PhoenixGTS]

I've looked long and hard at changing the 5th and 6th gear ratios to make the car a true 6 speed. I've found that the car bogs pretty bad when shifting hard from the top of 4th into 5th.

Here is what I would consider the ideal set up. 1-4 are stock, the current 5th gear becomes 6th gear, and a new .84 fifth gear is added (.84 gear is used on the Corvette tremec t.56)

Modified Viper T56 (2.66, 1.78, 1.3, 1.00, 0.84, 0.74)

My short 5th and 6th gears were done by my local tech using gears that came from Rockland Gear in New York. My tech later found that they are stock parts for the Aston Martin version of the tranny (he did have to turn a shaft down slightly for them to fit). I REALLY like them. Great mod, but dang expensive if you do not already have your tranny out and apart for some other reason (mine blew up the input cluster so it only cost me $1,000 extra to do the short gears). Nice even steps in the ratios from 4-5 and 5-6. With my shorter Gen II tires and 3.55 rear end 6,000 rpm in 6th = 200 mph with the probably top speed in 6th of 185-190 falling right in the peak of the power band about 5,200 rpm. Shorter 5th and 6th are a really nice mod even though my .80 and .64 ratios are not as short as you are talking about.

 

[Kai SRT10]

My short 5th and 6th gears were done by my local tech using gears that came from Rockland Gear in New York. My tech later found that they are stock parts for the Aston Martin version of the tranny (he did have to turn a shaft down slightly for them to fit). I REALLY like them. Great mod, but dang expensive if you do not already have your tranny out and apart for some other reason (mine blew up the input cluster so it only cost me $1,000 extra to do the short gears). Nice even steps in the ratios from 4-5 and 5-6. With my shorter Gen II tires and 3.55 rear end 6,000 rpm in 6th = 200 mph with the probably top speed in 6th of 185-190 falling right in the peak of the power band about 5,200 rpm. Shorter 5th and 6th are a really nice mod even though my .80 and .64 ratios are not as short as you are talking about.

I thought that the Aston gear was .62, not .64.

 

[Vipermann]

Couple more options:

The C6 Vette Auto runs .85 and .67 in 5th and 6th

or just put in the Vette Z51 gear set (if it can be done): 2.97, 2.07, 1.43, 1.00, .71, .57 ... it wouldn't make 5th any quicker, but looks like it would be good with the Viper 3.07s overall

 

[INSOMNIAC]

I have a 3.45 rear gear ... How difficult is it if I wanted to just change 3rd gear to a slight lower ratio (like a 1.23, as in the Ford GT)?

Very difficult. Whole transmission needs to come out and taken apart. Replace the gears, beef the slider hubs and clusters up while you've already taken the tranny apart. But again we are talking about breaking a Viper T56 transmission into parts and pieces.

Not worth going through just to change the 3rd gear ratio.