Ragtop 99

The Op's definition of midrange is probably in order to know what can be fixed.

There's a limit to what the cam can do without killing the top end. The intake manifold and LS3 port size influence how much midrange tq is going to be available, especially below 3500 rpm. If he's at 500 rwhp and 450 tq, he's well cammed.

Don't fear the gear.

StoplightWarrior

He knows that. He has a custom cam already but is looking for more w/o getting crazy on the cam (daily driver, CA concerns, and for what he uses the car for)

SgtRod

This is what I have heard from another person on the forum and thats why I fear the gear! I love low end punch but not if it will make me slow on the highway.

Ragtop 99

I have 3.90s. In 4th gear I can go to over 130 mph in 4th. If I were cammed I could go to 140 mph in 4th. A cammed car with 3.42s needs to hit about 145 MPH just to get to peak HP. If you are consistently going to exactly 160 MPH, then maybe 3.42s will be helpful. But the 3.90 car will pull on the 3.42 car to at least 135 mph, so need to be sure that you really will use the 140 - 160 mph in 4th gear in order to hope to catch up.

5knives

You'll have to define slow. While gears will lower your top end, they in no way make the car slow on the highway. When starting a run from a roll you have to choose the correct gear to run from regardless of your rear/gear ratio. The ratio may only change what gear you start from. Your power-band is still there you just have to find it. 4:10s, for example, will not limit the C6 to 140mph. The car still has the power and gearing to accelerate beyond that. I can understand people complaining about shifting too soon (although you did choose a manual, right) but using that same logic wouldn't that mean the car is getting thru each gear quicker and accelerating at a quicker pace? It can't be both ways. You can't shift sooner but be accelerating slower, that doesn't make sense. The issue comes with traction and driving. If these aren't addressed then you'll be slow even with stock gears and 150rwhp more. Gears have their pros and cons like anything else but they seem to be subject to more misinformed rumors than just about any other mod. A test drive is always best but can be hard to organize around your specific mod questions. And most people aren't going to let you run their $50k+ sports car to 140mph. Going by what you heard/read is only useful if that source of information is from experience and not just info being passed on from someone else who just heard/read it. So always consider the source. (that statement is not meant to offend anyone on here offering advice)

Basically you want to build your car around how you intend to use it. If you intend on mainly triple digit speed runs you have to decide how fast you actually plan on going and then choose your gear and power based on that. For 0-1XXmph runs gears are a great mod and are only limited by traction and your driving abilities. What Mr. Spinmonster said about speed of rotation is correct. Gears will break loose sooner but also re-grip sooner. Then it's off you go. 150rwhp more than stock will have you breaking loose too but wont re-grip as quickly. If you intend on only 100+mph highway rolls blow it and enjoy. Again build the car around your intended driving.

SgtRod

I hope that The Subfloor would chime in. He is a seasoned forum member with many applications under his belt.

Joe_G

Could not agree more. And while I used to have 3.90's, I now have 4:10's and highly recommend them. I doubted Spin once on that and now I know he's right. The 4:10's launch easier, it's noticeable.


These dyno sheets will explain why gears make the car feel like it's lost 500 lbs. Gears are my favorite mod.

Here is a comparative dyno sheet with a guy with same cam as mine, this was before my FAST but with 3.90 gears, he had a FAST but no 3.90 gears. Note how our cars are nearly identical.



Now, I changed the x axis to MPH vs RPM...note that at any given MPH, my geared car has about 30 more HP.



I have tracked fuel usage since new, and my car is a daily driver. The gears cut my mileage by exactly 1.0 mpg. Well worth it. Headers or a cam you only feel above 4000 rpm, you feel gears every time the car is moving. It feels 500 lbs lighter.

Oh and with my rev limiter set at 6800 I've gone 185 with 4:10's.. I could raise the limiter or get taller tires if I needed to go faster...but that is pretty fast in a vert.

SpinMonster

The key word is street tires. The gearing isnt what is causing the lack of traction. Increasing power breaks tires loose and handicapping gearing is about as smart as starting in third gear because you cant break it loose. 4.10's or 3.90's is effectively creating a gear ratio that is under first gear. If you did do a launch in 2nd gear and it broke loose, you cant rehook.....ever....until you come off the gas pedal. Same principal applies to 3.90's or 4.10's. keeping gears stock is the same as 4.10's and starting in 2nd gear.

If you calculate the final gear ratio, you will be amazed at just how close 4.10's in secod gear is to 3.42's in first. You arent faster because it doesnt break loose, you killed your 60'.

Its been my first hand experience that a geared car with less power will destroy an overpowered car with stock gears 0-60 or 0-100. i have found now at 800+rwhp that my car (a Z51 with 4.10's) hooks awesome in 1st gear and if it does break loose, it rehooks almost instantly. If my car with 700rwtq doesnt have a useless first gear then the gears arent the issue, the tire is when you match it with the wrong power level. Gears aid traction by rehooking way faster if you do break loose.

My age old statement: get gears and stop adding power when your tire choice doesnt let you get it to the ground.

If you keep stock gears with 50 more HP, the car will be slower.

Guys claiming useless 1st and 2nd gears are overpowered for the tire they use. They do not have too much gear. In fact getting 4.10's for such a car will show that it rehooks almost instantly. As a 471rwhp H/C car I was able to drop the clutch in 1st at 3500rpms and it would spin 1.5 rotations and hook with nitto 555r2s.

For those who didnt read it 100 times before. At 700rwhp my dart was running 11.2's at 138 with 4.30's spinning out of the line in 2 gears. With no changes, the car ran 10.9 with 4.88's and then 10.6 with 5.30's still spinning off the line. Thinking the same as forum members here refuse to change, I resisted but then went with a max of 6.13's and the car pulled a wheelie out of the hole cutting a 1.29 60' with a 9.97 at 138.

Gears where the only change and the common myth was of course since it was spinning with the 4.88's that it was overgeared. Believe what you want with power vs gears. My cars hook becuase I match the tire to the set up and cars get built from the back to the front. You gear for your trap speed and power has nothing to do with it.

Move the battery to the trunk, use a thinner front sway from the base car and use cheap 90/10 shocks and the only thing that will limit your launch is the 1/2 shafts and I have a collection of them broken. If you insist on street tires, that and only that is your limiting factor.

SpinMonster

I did 201mph at 6000rpms in 6th gear with 4.10's on my Z51. At my HP peak it would be 215.....I dont know why people think the top end is hurt by 4.10's.

SpinMonster

822rwhp here + 100 progressive shot on 4.10's and I dominate on the hiway.

Thinking about the concept you are saying, a car is faster in 3rd gear than it is in 4th gear, no exceptions. Now how can a car in a given gear then be fatser with 3.42's than 4.10's? The final gear raio of 4.10's in 3rd will pull like 3.42's in second.

I just dont see it.

My car lets all hell break loose on the hiway starting at 4000rpms in 3rd gear or 4th gear. 4.10's are the best thing on my car.....maybe its because I have the tire for it. In a hiway roll on, I just dont see anything other than being a gear higher with 4.10's as the 'down side' if it is one. I dont do 140mph races though.

SpinMonster

Subfloor runs an A6 and if you calculate the final drive ratio of 1st gear in his car that ran 9.9's, you will see he has lots of gear.

Gear ratios ..
....................A6.......MN6.......Z 51 MN6
First gear... 4.02...... 2.66..... 2.97
Second gear 2.36...... 1.78..... 2.07
Third gear... 1.53.......1.30..... 1.43
Fourth gear 1.15...... 1.00..... 1.00
Fifth gear... 0.85...... 0.74..... 0.71
Sixth gear.. 0.67...... 0.50..... 0.57
Final drive.. 2.56...... 3.42..... 3.42

The A6's first gear is plenty. The A6 with 2.73's is actually a bit shorter than a base C6 with a 4.10 rear gear set.

I dont see guys with 3.15's to 3.42's on the A6 complaining about it. Thats more gear than a Z51 with 4.10's.

Keep in mind he runs a 427 stroker with tons more low end Tq compared to a H/C car.

SgtRod

You cannot argue with the concept of gearing for the launch. It seems simple. My statement was not about tire spin or too much gear at launch. I just keep hearing some people (with gears) say that they run out of steam somewhere over 100mph. Ragtop99 said it himself. Unless it just perception that he lost steam in fourth.

Subfloor told me once that he raced his budy with similar HP, sub was geared and his budy was not(From a roll). He jumped out in front of the stock geared car but then his budy pulled him hard up top. Between 90 and 120. I cant remember.

I just want to know if there is a downside to gears up top. If so, where is it and how bad is it?

I am not an expert by no means and would not argue with any of the pros(Spin) about anything. i just want to know what to make of the statements about running out of steam at over 100.

This could help the OP's decision.

Joe_G

I don't think it ever runs out of steam. 11 seconds from 0-130 is pretty fast I think. Pulling 5th takes a while, but that is with or without gears - at 150+ aerodynamics plays a big role.

Judge for yourself if you think it runs out of steam over 100.

Ragtop 99

No, that's not what I said. Let me try again. Let's say we race (identical mods with a cam) except I have the 3.90s and you have 3.42s. My car will beat your car to 140 MPH as I have pulled through my maximum HP in 4th while your car is just getting there. My car will also beat your to a measured distance, say the 1/4 or 1/2 mile. At 140 mph when I shift into 5th, my rate of acceleration will slow down a bit as I drop back in the rpms and make less power. At this point you may start to close the distance between my tail lights and your front bumper. As we keep going I'm moving up in the rpms and gaining more HP. As the speed keeps going eventually you have to shift to 5th and will drop back in the rpms at a time when wind resistance is even higher and I'm now making more horsepower and I again start to pull on you.

Bottom line is my car spends more time in the high HP band. Yes, there are brief periods where you will accelerate faster than me, but those periods will not make up the difference. If we pick the optimal spot, you will be closer, but still looking at my tail lights.

5knives

An excellent explanation of what happens against a stock gear'd car. Those who complain about losing a roll-on because they ran out of gear probably started in the wrong gear to begin with so they never used the gears power-band to their advantage. That's not the gears fault. There will always be a slight drop during a shift but the stock gear'd car has to shift too, right? The distance it makes up during the gear'd car's shift is lost again when the stock car shifts and the gear'd car stays out front. I can't comment on what happens above 140+mph because I haven't had the ***** to try that on public roads but I have hit those speeds on the track and there was still plenty of pull left. (just no room)

SgtRod

Thats a good explaination. Thank you for taking the time to educate me.

HumanVette

Everything you all are saying make sense. I'm just still kinda dumbfounded. Every shop I called, ESC, IPS and DTE all told me with my HP and for roll racing I should go back to stock gearing, because I have enough power to pull me through the power band. ESC even told me they leave 3.42 gears in all of the supercharged cars they do. Now almost everyone in this thread is telling me it is the other way around.

Anyhow it is kinda to late for me, I already have my stage 4 DTE diff which I swapped out my 4.10 for 3.42, and they are getting ready to get installed. I just wish I could get to the bottom of this and find for sure what is right..


I don't mean to hijack your thread hungryhippo, I did try to post a few threads of my own, I just never got a lot of response.

hungryhippo

hehe, no hijack at all. this is all stuff i want to hear.

Joe_G

Sgt, I think you're local to me (I'm in Davie), perhaps one day we can hook up and you can take my car for a spin to see if gears are to your liking. We will likely be at PBIR on 12/11 for the Corvette Challenge if you can make it up.

glass slipper

If you're going to race from a dead stop, do the 4.10s...if you're going to roll race, do the 3.42s. Listen to ECS, IPS, and DTE as it's their business to know what's best and they're the only ones that are making any sense.