My 427SBC was able to hook fine on the street before I added the Procharger. At that time it was making 700+ flywheel horse power. The engine was 13.8:1 compression, AFR245 heads, a 274/286 @ 0.050" 704" lift roller, 1050 Dominator, etc. The car was a 3500 pound race weight '69 Camaro that ran 9.50's at 143 on a small shot of nitrous and mid 10's at 132 on the motor. It had 4.10 gears with 29X12 slicks or 29X14.50 Hoosier QTP's.
Effects of Gear Ratio on Traction
Car- 87 Monte Carlo with stock Buick GN Posi Rear End. 3:42 ratio. 275 45 17 Drag Radial, or 245 40 17 hard tire, which are about 26 inches tall.
The car weighs right under 3800 with me in it, and about 3/4 tank of gas.
Motor/Trans- 427 SBC with a solid roller. I forget exact specs, but somewhere around 260 @ .050. Decent CNC ported Dart Clones with a 227 runner, and flow about 315 @ .600. 10.6 to 1 static, and a 4L80.
Car gets driven lots of street miles on drag radials, and doesnt kill the tires unless I try to jump on it from a dead stop. Other than that, it hooks well on the street. I try to avoid spinning because the tires arent cheap.
But on hard tire, it will blow them off at will, so needless to say I just leave the sticky tires on it.
I feel the car will perform better all around with some 3:90s or 4:10s and I need to upgrade the center carrier/axles, and pin the tubes while Im in there anyway.
But my question is... Will the steeper gear affect my traction on the street?
My thoughts are the steeper ratio will give the powertrain a better mechanical advantage over the tires ability to hold it. But I have had a couple different people tell me the opposite, saying it will move the car better and not want to spin...
The car has pretty long legs, and does really good on the highway. And I know it will do better with some gear, but I dont want to make it squirrely either because the last thing I want to do is crash this thing!
The car weighs right under 3800 with me in it, and about 3/4 tank of gas.
Motor/Trans- 427 SBC with a solid roller. I forget exact specs, but somewhere around 260 @ .050. Decent CNC ported Dart Clones with a 227 runner, and flow about 315 @ .600. 10.6 to 1 static, and a 4L80.
Car gets driven lots of street miles on drag radials, and doesnt kill the tires unless I try to jump on it from a dead stop. Other than that, it hooks well on the street. I try to avoid spinning because the tires arent cheap.
But on hard tire, it will blow them off at will, so needless to say I just leave the sticky tires on it.
I feel the car will perform better all around with some 3:90s or 4:10s and I need to upgrade the center carrier/axles, and pin the tubes while Im in there anyway.
But my question is... Will the steeper gear affect my traction on the street?
My thoughts are the steeper ratio will give the powertrain a better mechanical advantage over the tires ability to hold it. But I have had a couple different people tell me the opposite, saying it will move the car better and not want to spin...
The car has pretty long legs, and does really good on the highway. And I know it will do better with some gear, but I dont want to make it squirrely either because the last thing I want to do is crash this thing!
1 - 20 of 26 Posts
You are absolutely correct in your thoughts.My thoughts are the steeper ratio will give the powertrain a better mechanical advantage over the tires ability to hold it.
If you can control it with your right foot, you might get better acceleration if you keep the thing hooked up. But it takes a little more finesse to keep things hooked up. It'll definitely move better once you're rolling. The tough part is not lighting the tires up.But I have had a couple different people tell me the opposite, saying it will move the car better and not want to spin...
For something that's street driven, with the tire sizes you're talking about, I like 3.73:1 or 3.90:1 gears. 4.10 isn't bad either, but you do start having to "walk on egg shells" when you're launching with anything over 4.
Thanks. I have learned alot here, and always remember how Bogie explains "mechanical advantage"
I have 3.90s in my truck, which weighs in right under 4000 pounds with me in it and it feels more responsive even with having less power.
Also I am really disappointed with my 1/4 mile times in the car. Im sure I can pick up .5 easy with just a gear change. It should do a little better than its 11.7 best et. Plus I will need to put it on a diet too, he he.
I have 3.90s in my truck, which weighs in right under 4000 pounds with me in it and it feels more responsive even with having less power.
Also I am really disappointed with my 1/4 mile times in the car. Im sure I can pick up .5 easy with just a gear change. It should do a little better than its 11.7 best et. Plus I will need to put it on a diet too, he he.
At the end of the day, "traction" is determined by the grip the tires have on the pavement and the weight transfer at launch. The gear ratio only determines how much torque is delivered to the wheels. Steeper gear means more torque means more able to overcome the grip of the tires on the pavement and thus easier to spin.
Have you got adjustable shocks and altered the upper control arm angle? More gear slows down the tire speed at an equivalent RPM, which I have been told can make the car move off the line slower.
To be honest, I do have double adjustable uppers but I just set them at the same length the factory ones were at. I haven't even checked pinion angle, or done a one bit of chassis tuning yet.Have you got adjustable shocks and altered the upper control arm angle? More gear slows down the tire speed at an equivalent RPM, which I have been told can make the car move off the line slower.
It sticks good at the track so far, my best 60 ft is 1.6, or 1.7.
I've been watching a bunch of Kevin Wilson's videos, so I have an idea of what I need to do when I finally get around to doing it!
I suspect the converter will be a factor. If it's big and tight, the engine will be pulling from a lower rpm and absorbing more torque with the faster 3.90/4.10 engine accel rate. On the other hand, a small dragstrip proper converter will let the engine flash higher into the engine's power band while absorbing less torque.
I'm not an automatic guy, but this stick shift graph shows how torque output can be affected by engine acceleration rate...
![]()
Despite the ratio difference, 1st gear only had 18ftlb more torque applied to the driveshaft while the engine was accelerating.
Grant
I'm not an automatic guy, but this stick shift graph shows how torque output can be affected by engine acceleration rate...
Despite the ratio difference, 1st gear only had 18ftlb more torque applied to the driveshaft while the engine was accelerating.
Grant
Thanks! Forgot to mention the converter. It is a freak Show 9-in 3200 stall converter. But in this application it does Flash right about 4,000 RPM. Right now I'm having some other issues tuning this EFI so it's not really coming out of the hole really hard yet at the track. But yet, another thing I'm trying to get dialed in.I suspect the converter will be a factor. If it's big and tight, the engine will be pulling from a lower rpm and absorbing more torque with the faster 3.90/4.10 engine accel rate. On the other hand, a small dragstrip proper converter will let the engine flash higher into the engine's power band while absorbing less torque.
I'm not an automatic guy, but this stick shift graph shows how torque output can be affected by engine acceleration rate...
View attachment 630258
Despite the ratio difference, 1st gear only had 18ftlb more torque applied to the driveshaft while the engine was accelerating.
Grant
Based on you guys is excellent suggestions, when I pull the trigger I'm going to go with some 410s, an Eaton Truetrac, and some 30 spline axles!
And this old guy out here that used to work on a Cup team, showed me how to pin these rear axle tubes!
And this old guy out here that used to work on a Cup team, showed me how to pin these rear axle tubes!
I drill through the center casting and tube in 3 places on each side and the tap for a 7/16-20 bolt, install the bolts with lots of red loctite.Based on you guys is excellent suggestions, when I pull the trigger I'm going to go with some 410s, an Eaton Truetrac, and some 30 spline axles!
And this old guy out here that used to work on a Cup team, showed me how to pin these rear axle tubes!
Yep, that's exactly how he does it. He specialized in rear ends on a cup team years ago, now he just has his own little shop out here in the sticks.I drill through the center casting and tube in 3 places on each side and the tap for a 7/16-20 bolt, install the bolts with lots of red loctite.
He's the one that shortened my aluminum driveshaft for me. Charged me $85, when it was going to cost me over $200 to do it everywhere else..
Make sure you give Michael at Freakshow a call and see if he thinks restalling your converter might be beneficial after the gear change. And, more rear gear/ slightly different converter may increase your desire to want to plumb in a supplimental trans cooler, if not so equipped
Not sure if you are bragging or actually have a question. Up to a point I'd say yes, but with the 427 ci displacement, I'm gonna say that traction is all about the angle of the GO pedal.
You say that the car is driven lots of miles on drag radials, with that weight of car the only change will be the MPG. Yes, this is Hotrodders, but you did ask. It'll only go down.
You say that the car is driven lots of miles on drag radials, with that weight of car the only change will be the MPG. Yes, this is Hotrodders, but you did ask. It'll only go down.
Make sure you give Michael at Freakshow a call and see if he thinks restalling your converter might be beneficial after the gear change. And, more rear gear/ slightly different converter may increase your desire to want to plumb in a supplimental trans cooler, if not so equipped
I am able to live record my phone screen, so I did it on a couple of passes. As soon as I stabbed the throttle, RPMs came up to 4000 and climbed from there.
I am happy with the converter, but I will call Michael and chat though. Because it does seem a little tight when staging, but man it works really good on the street!
Like Ericnova explains it, you don't even know there is a hi stall converter until you stab the throttle.
The main reason Im thinking it needs a little more gear besides the fact that it will be more responsive everywhere, is when I let off after the stripe, it was barely getting into 3rd gear and it showed about 5500 rpms.
(Should be 5000 in a straight drive with 3.42 a 26 inch tire in 3rd gear 1:1 @115 so 5500 in an automatic sounds about right)
Im thinking if I could go across the stripe with its tongue hanging out at the top of 3rd gear instead of just coming into 3rd and then letting off, it will have more time up on the cam. (thanks Bogie!)
So far it seems happy shifting around 6800. And when its running right it pulls right up even past 7k.
I spent alot of money on this thing and it should be getting better mph than just 115.
get on the gear speed chart before buying gears. you are setting it up for racing. in street trim gears will knock off a 1/10 or less.
remember the 10 extra pounds at the driveshaft is still multiplied by rear ratio
remember the 10 extra pounds at the driveshaft is still multiplied by rear ratio
There is so so SO much you need to play with before changing gear ratios.
Here is the thing. I don't care if your putting down 100hp or 1000hp if you cant get it down your wasting power to make smoke. Smoke is bad that is the tire loosing traction.
Traction and grip are all about power management. Go back to the basics and get video of things. Watch how the car launches and what it is doing during the launch.
Is it squatting a tire hard? What happens at different pressures?
Is it tilting to one corner in the rear? Why? Is something preventing travel, to stiff, to soft?
Is it getting air under the front tires? How do you fix that? Keeping those tires coming down slow and coming up slow can save you not only time but also keep you off the wall/out of the ditch.
Oh an where do you want grip? Something set up to go in a straight line is going to require a totally different often uneven suspension then one set up to go through winding "35mph street speed" curves at 120mph requiring a more equal suspension.
Traction starts with the suspension. The tires and the gear ratios come second.
This might come off as critical.
I am just trying to keep you from throwing parts at something before you need them or buying the wrong parts for the application.
You can have two identical cars sitting side by side with the same exact amount of parts. If one is not tuned to take full advantage of the parts then it will be looking at the taillights of the other a majority of the time.
The best parts mean nothing without proper tuning of those parts.
Now back to power management. Most times less "power" can lead to faster times. Here is the thing. Your parts have limits. The tires can only grip the surface so well. The suspension can only keep those tires gripping the surface so well. The transmission has a point where it will need to shift and there are losses there. Often those shifting losses can be a major factor. Generally the more power your making the higher the loss is going to be be at that shift. Unless your tuning to reduce those losses. I won't even go into aerodynamic influences or how some drivers just dont know how to use things properly. ie If the engine is meant to shift at 6200 and everything tuned to shift at 6200 and the idiot/converter is shifting at 3500 well things are going to suffer. On the other hand if they switch cams etc and it now drops off at 5500 instead of 6400 etc. Well that 6200 converter is not going to like that and things are going to suffer there also.
I am not going to tell you X.xx gearing is going to save you a tenth over X.xx gearing because there is a pretty good chance it is not. Get the car tuned with the gearing you have looking for losses in other areas. Like suspension or shifting. Once you get those dialed in then you can look at changing ratios and changing power levels.
It is not one thing that makes the car fast it is the collection of parts tuned to work together within the limits of those collection of parts that makes things fast.
Do little things at a time and record things (paper notepad in the trailer/car) you do along with the weather/surface(and any prep). This will let you change things back if you make things worse or if the conditions change. It will happen it is part of tuning. But if you do lots of things at once then plan on a few headaches to figure out what is causing you to loose a full second etc.
Here is the thing. I don't care if your putting down 100hp or 1000hp if you cant get it down your wasting power to make smoke. Smoke is bad that is the tire loosing traction.
Traction and grip are all about power management. Go back to the basics and get video of things. Watch how the car launches and what it is doing during the launch.
Is it squatting a tire hard? What happens at different pressures?
Is it tilting to one corner in the rear? Why? Is something preventing travel, to stiff, to soft?
Is it getting air under the front tires? How do you fix that? Keeping those tires coming down slow and coming up slow can save you not only time but also keep you off the wall/out of the ditch.
Oh an where do you want grip? Something set up to go in a straight line is going to require a totally different often uneven suspension then one set up to go through winding "35mph street speed" curves at 120mph requiring a more equal suspension.
Traction starts with the suspension. The tires and the gear ratios come second.
This might come off as critical.
I am just trying to keep you from throwing parts at something before you need them or buying the wrong parts for the application.
You can have two identical cars sitting side by side with the same exact amount of parts. If one is not tuned to take full advantage of the parts then it will be looking at the taillights of the other a majority of the time.
The best parts mean nothing without proper tuning of those parts.
Now back to power management. Most times less "power" can lead to faster times. Here is the thing. Your parts have limits. The tires can only grip the surface so well. The suspension can only keep those tires gripping the surface so well. The transmission has a point where it will need to shift and there are losses there. Often those shifting losses can be a major factor. Generally the more power your making the higher the loss is going to be be at that shift. Unless your tuning to reduce those losses. I won't even go into aerodynamic influences or how some drivers just dont know how to use things properly. ie If the engine is meant to shift at 6200 and everything tuned to shift at 6200 and the idiot/converter is shifting at 3500 well things are going to suffer. On the other hand if they switch cams etc and it now drops off at 5500 instead of 6400 etc. Well that 6200 converter is not going to like that and things are going to suffer there also.
I am not going to tell you X.xx gearing is going to save you a tenth over X.xx gearing because there is a pretty good chance it is not. Get the car tuned with the gearing you have looking for losses in other areas. Like suspension or shifting. Once you get those dialed in then you can look at changing ratios and changing power levels.
It is not one thing that makes the car fast it is the collection of parts tuned to work together within the limits of those collection of parts that makes things fast.
Do little things at a time and record things (paper notepad in the trailer/car) you do along with the weather/surface(and any prep). This will let you change things back if you make things worse or if the conditions change. It will happen it is part of tuning. But if you do lots of things at once then plan on a few headaches to figure out what is causing you to loose a full second etc.
Thanks Cerial.
What has me thinking is, last time my best time was 11.7 with the 2004R which was shifting way too soon and the motor was running like crap because of a bad coil and fouled out Spark plugs. I think I remember it having a 1.7 60 ft.
This time out I have my 4l80 installed and it shifts exactly where I want it to, but now my best 60 foot was 1.8 as far as I could tell it was not spinning. Also the ET was 11.9. Mph was about the same.
Now, there is one thing as far as tuning that I do need to address for sure. There is a header flange gasket leak that I cannot hear, but I can see where it's shooting out black soot onto my number five Spark plug. Also some pin holes at The Collector, near where the O2 sensor is mounted. The car does load up when it's sitting, and could use a new set of plugs in it now. The more I think about it, these tiny exhaust leaks may be the problem with the rich condition at idle. Once I'm on the road and driving it clears up, but it seemed like it wasn't clearing up at the track.
The car did not like sitting in the staging Lanes, being shut off and turned back on again.
So yes, I'm definitely going to work on these , and get it running right before I do any drastic changes.
The car runs really strong as it is out on the road, but the loading up at stop lights and in the staging lane thing needs to be fixed first for sure.
Basically the whole point of this post was so I don't make a mistake and put some steep gears in it and turn this thing into a burnout machine, when it doesn't have any traction problems right now. Because I know for sure that spinning ain't winning! And the big block torque this thing puts out should be okay with 3.42 gears anyway.
So thanks to all who have helped me along the way, and keep the ideas coming!
What has me thinking is, last time my best time was 11.7 with the 2004R which was shifting way too soon and the motor was running like crap because of a bad coil and fouled out Spark plugs. I think I remember it having a 1.7 60 ft.
This time out I have my 4l80 installed and it shifts exactly where I want it to, but now my best 60 foot was 1.8 as far as I could tell it was not spinning. Also the ET was 11.9. Mph was about the same.
Now, there is one thing as far as tuning that I do need to address for sure. There is a header flange gasket leak that I cannot hear, but I can see where it's shooting out black soot onto my number five Spark plug. Also some pin holes at The Collector, near where the O2 sensor is mounted. The car does load up when it's sitting, and could use a new set of plugs in it now. The more I think about it, these tiny exhaust leaks may be the problem with the rich condition at idle. Once I'm on the road and driving it clears up, but it seemed like it wasn't clearing up at the track.
The car did not like sitting in the staging Lanes, being shut off and turned back on again.
So yes, I'm definitely going to work on these , and get it running right before I do any drastic changes.
The car runs really strong as it is out on the road, but the loading up at stop lights and in the staging lane thing needs to be fixed first for sure.
Basically the whole point of this post was so I don't make a mistake and put some steep gears in it and turn this thing into a burnout machine, when it doesn't have any traction problems right now. Because I know for sure that spinning ain't winning! And the big block torque this thing puts out should be okay with 3.42 gears anyway.
So thanks to all who have helped me along the way, and keep the ideas coming!
If you're showing 5500 RPMs with the 3.42:1 gears, then at the same speed, you'll be at ~6,600RPMs with the 4.10:1 gears.The main reason Im thinking it needs a little more gear besides the fact that it will be more responsive everywhere, is when I let off after the stripe, it was barely getting into 3rd gear and it showed about 5500 rpms.
But, with more area under the curve, you'll likely be going faster. How much faster is hard to calculate exactly. If it pulls to 7000 RPMs and a little beyond, you might not run out of revs. Your ET and top speed should imrpove with the 4.10:1 gears for sure.
That's kind of what I was thinking too. And even though the car makes a lot of torque, it's really got some good top end on it too. And it's not a really light car either, in the grand scheme of things. And like others have said about the right foot and traction. If it does break loose too easy, I will just have to do that right foot modification!If you're showing 5500 RPMs with the 3.42:1 gears, then at the same speed, you'll be at ~6,600RPMs with the 4.10:1 gears.
But, with more area under the curve, you'll likely be going faster. How much faster is hard to calculate exactly. If it pulls to 7000 RPMs and a little beyond, you might not run out of revs. Your ET and top speed should imrpove with the 4.10:1 gears for sure.
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