3:55 rear end dragstrip improvement?

[Bugman Jeff]

And like I said, I prefer to look at all this in terms of Thrust, so if we plug in the stuff from the table above, here's what the numbers from a stock Viper GTS look like:
Gear Peak Thrust (in pounds)
1st 3200
2nd 2180
3rd 1610
4th 1200
5th 890
6th 600

So, if thrust is 3200 LB, and the car weighs about the same, does that meas that the Viper accelerates at 1g in first gear?
Just wondering.

[Joel]

The technical aspects of all this are fine if you are accelerating at full bore all the time and that is your main concern. What is more important to me is if you look at the shift points of a lower gear, you can imagine that you have more push with a lower gear than a higher gear. That's what made it more fun for me. Most of the driving you probably do is well below 70 mph unless you are on the interstate or just like to push your luck. As I said before, the fun factor is much better with the lower gear and it makes 5th and 6th gear usable. You know how you drive your car and if it suits you now, you just saved yourself a pile of money.

The last three post seem quite helpful, for what I do and don't do, I think the stock gears will stay put.

[Steve M]

You know how you drive your car and if it suits you now, you just saved yourself a pile of money.

Bingo.

I went down the gears path previously with my 2002 Camaro when I switched from 3.42s in a 10-bolt to 4.11s in a 12-bolt. Honestly, it's the mod I regretted the most with that car - not only was the gear set noisy (totally an installation error from Strange), but the lack of traction in 1st gear on regular street tires and the 2,000+ RPMs cruising down the interstate really took the fun out of the car. It wouldn't be quite that bad with 3.55s in a Viper, but it's such a personal preference. If I was going to consider another gear swap, I'd do my best to see if I could take a ride (or drive) in one with gears before making my final decision.

[Tom, F&L GoR]

Please - I did not write the article, I copied it from an old VCA PacWest chapter website and saved it. I pasted what I saved here. I am not the author.

[stuntman]

I found the article:

http://www.viperclub.org/howto/faqs/...-gear-swap.php

Although the Rear Wheel Torque vs. Speed Graph is a bit confusing. The math before the graph states:

450 ft-lb x 2.66 First gear ratio x 3.07 rear end gear = 3670 ft-lb
450 ft-lb x 2.66 x 3.73 = 4460 ft-lb
546 ft-lb x 2.66 x 3.07 also = 4460 ft-lb

Yet the 1st gear with the 3.07 final drive (in blue) is peaking around 4,200 ft-lb which does not correspond with the math above.


After my own calculations and analysis of the thrust curves using my car's own dyno numbers (with K&N and smooth tubes), a 3.31 with the Gen IV/V 5th and 6th gear ratios (0.81 and 0.63) sounds like the hot ticket.

3.55s are better to 125mph, but is worse above 125mph (overall the gains below 125 probably outweigh the losses above) on a road course, while 3.73s are very beneficial below 100mph, but is worse above 100mph and it's probably not as good of a choice for the road course as 3.55s or 3.31s.

0.02

[Joel]

3.31's no longer available.

I found the article:

http://www.viperclub.org/howto/faqs/...-gear-swap.php

After my own analysis of the thrust curves, a 3.31 with the Gen IV/V 5th and 6th gear ratios (0.81 and 0.63) sounds like the hot ticket. 3.55s aren't bad but I don't think 3.73s are very beneficial since they pretty much shift every speed range up one gear.

[stuntman]

No one makes them? I'm sure you could get them cut worst case.

[Joel]

The article was great -- I didn't mean to denigrate you or the article and I appreciate you posting it. It was very informative. My point was only that most folks don't drive full throttle all the time and so some of the findings, while accurate from a technical standpoint, don't reflect actual driving we do in the cars.

Please - I did not write the article, I copied it from an old VCA PacWest chapter website and saved it. I pasted what I saved here. I am not the author.

[Matt Dillon]

Just going from red lite to red lite, do ya'll think the 3.73's would be even better that the 3.55's (on my 00' RT/10 HF Cats & smooth tubes, other than that pretty much stock). Thanks!

[Vprbite]

I know at least one person here in town with 3:73 who thinks I would be stupid to waste my time with 3:55s and I should do 3:73. I think going higher than 3:55 is bonkers unless you are running a taller rear wheel and tire that effectively reduces the gear ratio back down.

So, Matt, to answer your question definitively I don't know. But my educated guess is that if all you wanted was "woo hoo's" and tire squeals around town, then, probably.

I had 3:55s in my 2002 with smooth tubes, High Flows and Corsa and loved em. And I still did 165 just fine with that. But with 3:73s you are gonna light those tires up like they aren't there and it may hurt resale a bit, if you care about that.

[stuntman]

Assuming you can get the power down in 1st gear, the 3.73s will be faster until the top of 3rd (95mph) and possibly the top of 4th (124mph).

If you're trapping >124mph in the 1/4 mile, then 3.73s will add another shift and you'll have to be in 5th. 3.55s top out at 130mph in 4th gear while 3.31s top out at 140mph in 4th.

[Vprbite]

Assuming you can get the power down in 1st gear, the 3.73s will be faster until the top of 3rd (95mph) and possibly the top of 4th (124mph).

If you're trapping >124mph in the 1/4 mile, then 3.73s will add another shift and you'll have to be in 5th. 3.55s top out at 130mph in 4th gear while 3.31s top out at 140mph in 4th.

But it appears Matt doesn't really care about what he might trap at, just fun from red light to red light which means he has a different decision to make than someone who drag races. He indicates he has 3.55s already so it would seem to me he is hankerin for 3.73s as he will get more "woo hoo's" as I put it.

Matt, give Jon B a call and he will get you all set up. Just remember (and I'm sure he will remind you of this too) to change your fluid more often. And I don't think I would track (road course) with 3.73s without a diff cooler but again, it doesn't sound like that worries you so, have at it and let er rip!

[Bugman Jeff]

One of the things I see over and over again regarding 3.73s is the lack of traction in 1st gear. My question is how is it any different than having a high HP car? An FI or even well built heads/cam car will overpower 1st gear with no trouble too. Either way, you've got to use a lot of throttle management and 3.73s will give you more bang for the buck. I'm not trying to be argumentative or advocating 3.73s, just trying to understand some of the common complaints.