3.55 or 3.73 gears for Viper T56 / 26" tires

[BANKO]

Hey Guys, I'm trying to decide what gears to run in my car. I currently have 3.08s / Viper T56 with the following ratios:

1st 2nd 3rd 4th 5th 6th Rev
2.66:1 1.78:1 1.30:1 1.00:1 0.74:1 0.50:1 2.90:1

I'm running the Michelin Pilot Super Sports: 295/30/19 @ 26"

Using the Tremec calculator (http://www.tremec.com/calculadora.php)

@ 2000rpm, 3500rpm, & 5000rpm I get the following speeds. The variation at my power band is only 5 - 7mph

My goal is to have improved hookup for the auto-x, and stronger pull in the 4th / 5th gear for the high speed track events.

I'd appreciate your thoughts....

40970 40973

40971 40974

40972 40975

[Sieg]

What do you have for motor?

Sweet spots for:
- Rpm
- Torque
- Cruise/fuel economy

What do you anticipate your percentages of auto-x / track usage vs. general road usage?

With the Vipers semi-wide ratio I'd be leaning to 3:73, but 3:55 gearing will typically provide more traction.

With my close ratio T56 mag I'm leaning to 3:55 with a 26.4" tire. The reality is even though my desire is to track and auto-x it, the car will be spending a much larger percentage of it's time on public roads so that's where I'm focusing on optimizing the ratios. My motor likes to cruise at 2,200 so 5th is for 60-65 mph, and 6th is for open range cruising since 2,200 is about 82 mph.

Without a quickchange rear end we'll always be compromising somewhere.

[BANKO]

Hey Sieg, thanks for the thoughts!

I'm currently running an old school SBC - 200 RWHP / 285 FT-LBS Torque which I don't think will hold more than 5000RPM with much abuse. Planning on a 525 FWHP LS3 with a 6600RPM redline in the coming year.

I think it will spend most of it's time on public roads with cruises to auto-x and track events. I don't think I'll notice much difference in the 1 -> 2 shift between the 3.55s and 3.73s. My current 3.08s are fine for around town, but I know I am leaving a lot of acceleration on the table with such a tall gear. I'm not concerned about fuel economy, it is smiles to the gallon I monitor ;-) I do like cruising around 2000RPM so 80MPH is more than sufficient.

I'm thinking I would be happy with either but won't consider going lower like 3.93 or 4.11.

[Flash68]

With the Vipers semi-wide ratio I'd be leaning to 3:73, but 3:55 gearing will typically provide more traction.



Agreed, and based on the modest power plans, I would opt for the 3.73 as well.

[Sieg]

With your motor I'd probably go to 3:73 for maximum power leverage. Then see how they feel in the LS.

I was paying close attention to my rpm today on a typical trip to town and favorite backcountry loop and it's a fine line between 3:55's and 3:73's. I've been speculating on this too long, the 3:73's may win. 2250 rpm with my .63 6th and 26.5 tire is 75 mph, 2500 rpm is 85 mph.

The good thing about your trans is it doesn't have the low first gear........I've never understood why you'd want lower than the 2.66. Maybe really slow parades? :sieg:

[FETorino]

With your motor I'd probably go to 3:73 for maximum power leverage. Then see how they feel in the LS.

I was paying close attention to my rpm today on a typical trip to town and favorite backcountry loop and it's a fine line between 3:55's and 3:73's. I've been speculating on this too long, the 3:73's may win. 2250 rpm with my .63 6th and 26.5 tire is 75 mph, 2500 rpm is 85 mph.

The good thing about your trans is it doesn't have the low first gear........I've never understood why you'd want lower than the 2.66. Maybe really slow parades? :sieg:

Actually I've never understood the .50 6th gear:headscratch:

A 4.10 rear gear will give you a 10.9 SLR which will make the car easy to drive on the street in slow speed stuff no matter what clutch or flywheel.

At 2200 rpm in 6th gear with a 26" tire you should be doing 83 mph so that seems like a nice hwy cruiser. At 2000 rpm you'd still be doing 75.5mph. I don't own an LS but I hear a mild one is happy at really low rpm so maybe less rear gear and running down the hwy below 2000 rpm makes the LS engine happy.

I'd choose between a 3.89 and a 4.10 especially if you aren't upgrading the motor soon. JMHO

:cheers:

[Payton King]

Help get the car moving with the lower power level. I had 4.11 in mine and in 6th at 65 I was turning 1750 rpm with a 27 inch tall tire. Had 3.80's in and would turn 1500 at 65. Big pain with the 3.80 if I slowed up from 65 in 6th I had to down shift. I highly doublt you will make it into 5th on a road course with the power level you are currently at.