Why 3.07 gears in the Viper

[AZVIPER]

I have a 2004 RT10 and it had 3.07's. Hated them. Went to 3.73. Want a difference. Fourth gear now pulls like second. Ave MPG was 12.3. Only ran one tank thru so far and it was 14.05. RPM at 60 in 5th is 2000 rpm and 1750 in 6th.

 

[Vipermann]

3.07's work great on the track. Just this weekend, one of our guys who had a set of 3.33's installed had to shift into 5th in the front straight due to the lower gears and shorter track tires while I could remain in 4th with my 3.07's, much to his disadvantage. His car is going back into the shop to swap back to 3.07's.

What track? It would kind of depend on the track. To run out of gear in 4th with 3.33s would have to be at very high speeds that most people would not regularly be driving at (when I ran the 1/4 mile, I was just shifting into 4th at 123+ mph at the end) -- certainly not often enough to give up the acceleration gains in 1st and 2nd gear, and the benefit of having highway crusing in 6th be a bit more livable.

As the SRT engineer said in an earlier forum chat, the stock 3.07s were basically chosen for EPA ratings (not performance)

 

[redtanrt10]

What track? It would kind of depend on the track. To run out of gear in 4th with 3.33s would have to be at very high speeds that most people would not regularly be driving at (when I ran the 1/4 mile, I was just shifting into 4th at 123+ mph at the end) -- certainly not often enough to give up the acceleration gains in 1st and 2nd gear, and the benefit of having highway crusing in 6th be a bit more livable.

As the SRT engineer said in an earlier forum chat, the stock 3.07s were basically chosen for EPA ratings (not performance)

We were all at Willow Springs (CA), which is very fast. In my car w/3:55's I hit the rev limiter on the front straight in 4th.

 

[Nader]

At Pocono you are at the upper end of 4th gear in the straight also with the stock gears.

 

[JonB]

I have a 2004 RT10 and it had 3.07's. Hated them. Went to 3.73. Want a difference. Fourth gear now pulls like second. Ave MPG was 12.3. Only ran one tank thru so far and it was 14.05. RPM at 60 in 5th is 2000 rpm and 1750 in 6th.

-Wheelspin is dangerous 1-2 with 3:73 at 475+ HP
And On the advise of key folks at Team Viper, I caution AGAINST a 3.73 because:
-Loads on output tranny shaft bearings are way above design. +7--15% is ok, not +22%.
Resulting tranny heat needs to be dealt with = lube severe service cycle or tranny cooler;
-rear diff heat increases dramatically with 3:73. = Severe service cycle or cooler.

Dont get me wrong: I like the 3:73 in Gen 1 Vipers with 400-425HP. But the heat issues remain. I find the 3:73 has "frantic" acceleration above 475-500 HP, hard to manage.
A major complaint of Supercharged Vipers.... "Got HP - Cant Use It." Same w/ 3:73.

One final nit-pick: 3:07 was only indirectly chosen for economy. It was directly chosen to acheive a GAS GUZZLER TAX economy target. The goal was to minimize TAX, not maximize MPG....but the chicken-egg aspects of the debate remain. The TAX goal drove the MPG goal.

 

[evomind]

ive driven 3.55s and 3.33s.
though i can see why many folks like the 355s, i happen to prefer the 3.33s just a tad more.
the differences are subtle but i prefer the 3.33. i believe its just a little better all around gear for my car.

 

[SNKVENOM]

I agree with JonB. I have 3.73’s in my 98. 1st gear is almost unusable out of the hole and 2nd is even more dangerous. You almost always go sideways even if you get a little aggressive. It’s an absolute panic until you hit 3rd. This Winter I am looking at a S/C and these gears are out…..and in with the 3.07’s.

 

[Vipermann]

I want to be clear too ... the SRT-10 puts out awesome performance even with the stock 3.07s.. I just think that, overall, you can't go wrong with 3.33s. The fact that the 2008s will have a higher redline makes an even better case for 3.33s, since you will be able to hold each gear a bit longer ... the cake and eating it too.

 

[Viper X]

Viperman,

Mike and I were at Willow Springs as he says above. Granted that this is a fast track, but even with 3.07's, I was at 6000 rpm in 4th gear just before the end of the straight every single time. I had to hold that speed for a few seconds, not wanting to shift into 5th and then back to 4th again at that speed going into a 90 degree left turn. Speeds were about 140 mph - ish. Track tires tend to be a bit shorter than stock tires, affectively lowering the top speeds achievable in each gear.

On the one occaision that I had to go higher - racing a new Z06 down the straight, I spun it up to 6300 rpm just to make sure I got him. That's about 145 - 147 mph (I wasn't looking at my speedo at that time). Yes, I got him as usual and no, my GTS isn't stock.

The point is, that on some road courses, the 3.07's work very well and give you an advantage over other cars.

Dan

 

[alpha85]

I put 355's in my 05 about a year ago. It is more driveable around town and on the highway. Mileage is a little worse around town a little better on the highway. Mainly because you are in 6th gear at 70mph. At the track you have to shift more. No difference in times vs 307's.

 

[Vipermann]

Viperman,

Mike and I were at Willow Springs as he says above. Granted that this is a fast track, but even with 3.07's, I was at 6000 rpm in 4th gear just before the end of the straight every single time. I had to hold that speed for a few seconds, not wanting to shift into 5th and then back to 4th again at that speed going into a 90 degree left turn. Speeds were about 140 mph - ish. Track tires tend to be a bit shorter than stock tires, affectively lowering the top speeds achievable in each gear.

On the one occaision that I had to go higher - racing a new Z06 down the straight, I spun it up to 6300 rpm just to make sure I got him. That's about 145 - 147 mph (I wasn't looking at my speedo at that time). Yes, I got him as usual and no, my GTS isn't stock.

The point is, that on some road courses, the 3.07's work very well and give you an advantage over other cars.

Dan

Got it. And the shorter track tires makes a good point about the effective track gearing.

But, in the context of the street (and taller street tires), I'd guess that Dodge would have posted better magazine comparison numbers (0-60, 1/4 mile, etc.) with 3.33s ... and I'd also say that such a faster factory Viper, albeit with a bit lower EPA rating, would have made Vper nation just a tad more proud. (Lambo and Ferrari don't compromise their objective of generating performance results for the sake of the EPA rating.) ...

Said another way, I bet Dodge would sell more Vipers, even with the higher gas-guzzler tax but with lower 11.5-11.6 1/4 mile times, and clearly stomping the Z06 in the magazine comparisons, than they currently will with the 11.7-11.9 1/4 mile times as posted in the magazines.

On the STREET, the stock Viper (with 3.07s) does bog down in 1st and 2nd gear if you don't launch it just perfectly ... and 6th gear is an 'aquired taste' at speeds of 70mph or less ... thus, Dodge could have made the stock Viper with 3.33s for the 90% of owners who will never see 140mph in 4th gear at the end of a track straight, and then the true track folks (the other 10%) could have always swapped those gears out for some 3.07s.

My $.02.

 

[Big Medicine]

Gears multiply torque.

Full Stop.

This is always true, everywhere on the planet Earth.

Torque multiplication is very useful until you are in your power band, that is to say, in low rpm situations. Once rpms come up, you have the power you need.

So, the short gears are good in first gear. If you road race only in first gear, drag race with sticky slicks, or are towing boats with your Viper, gears may be for you.

 

[VIPER R]

If you're doing basically street driving you probably won't feel much difference between 3.07 and 3.33. I would probably go for 3.45 if I did it over. That's with a Paxton and exhaust.

 

[Vipermann]

If you're doing basically street driving you probably won't feel much difference between 3.07 and 3.33. I would probably go for 3.45 if I did it over. That's with a Paxton and exhaust.

I had 3.45s in my '05 with about 475 rwhp. The car moved through the gear too easily (not enough load to gain the full power of the engine, before each up-shift, which came too quickly). I then switched to 3.33s -- perfect -- and definitely better than the stock 3.07s.

 

[Vipermann]

Gears multiply torque.

Full Stop.

This is always true, everywhere on the planet Earth.

Torque multiplication is very useful until you are in your power band, that is to say, in low rpm situations. Once rpms come up, you have the power you need.

So, the short gears are good in first gear. If you road race only in first gear, drag race with sticky slicks, or are towing boats with your Viper, gears may be for you.

Torque is not static, i.e. the torque curve is never perfectly flat from initial rpms. The is also an issue of momentum. HP measures the rate at which the engine develops torque. If an engine is momentarily over-loaded, and bogs down, even in 2nd gear, then the engine is momentarily 'trapped' at a lower level of HP and thus not developing torque as quickly, i.e. slower. If there is no 'bogging down' (step on the gas and feel the delay), then there is no benefit of shorter gears. But if there is a 'bogging' delay when the throttle is applied, in ANY gear, then a shorter gear helps the engine get up toward peak HP more quickly and thus develop more torque. This generally makes a car faster, depending upon the trade-off between faster engine speed vs. the time required for actual shifting (as more shifts may be required for any given distance).

I my simple real-world test, if you're not able to get your right hand from the shift knob to the wheel and back to shift again, in the time it takes to accelerate to the engine redline (in any gear and without wheelspin), then you've got too short of a gear. For 3.73s and 3.55s, I think this would always be the case, thus I don't think the SRT10 benefits from those gears. Not so with the 3.33s, from my experience, which feel like the sweet spot ... and whereas the 3.07s DO seem to bog the car down (at near stock power levels). Got Paxton? Then disregard.

An engine's power would be optimized if it could always operate up near it's peak HP and torque, but it would require many transmission gears and constant shifting to do so. And whaala, that gets to the benifits of the relatively new technology of CVT, continuously variable transmissions, although these new designs seem less robust right now and limited to much lower power applications for the time being. (Interestingly, I think Lexus just came out with an 8-speed automatic.)

 

[FE 065]

I had 3.45s in my '05 with about 475 rwhp. The car moved through the gear too easily (not enough load to gain the full power of the engine, before each up-shift, which came too quickly). I then switched to 3.33s -- perfect -- and definitely better than the stock 3.07s.

I just can't imagine being able to feel the SOTP difference on the street-in any kind of driving, between a 3.33 and a 3.45.

Much less, to warrant a change in opinon as wide as from "over-geared" to "perfect"; with that being the only change.


- But I'm happy if you're happy

 

[Vipermann]

Well, it did, and I am. And the 3.33s definitely felt quicker than the 3.07s.

But I will tell you that being a convertible, with side exhaust seems to exaggerate any differences -- your ears hear how much the engine is winding up (more so with the 3.45s), and your mind seems to expect the car to be moving at a certain speed for a given amount of 'noise.' I didn't like hearing too much engine growl from higher rpms without as much SOTP (and wind in your hair) movement ... for what it's worth