Speed in Gears - Dodge Ram SRT-10 Forum
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post #1 of 34 Old 10-16-2005, 04:27 PM Thread Starter
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Speed in Gears

Updated on 2/8/06 for 4.88 gears.

The question of top speed, speed with 4.11, 4.56, 4.88, 5.13, 5.38 rear ends, and speed in gears keeps coming up. I figured I would compile it in one spot and then ask Roktman to make it a sticky.

The data for the 4.11 is straight out of Car and Driver. I extrapolated the speeds for the other gear ratios from that data. I also dropped the Transmission Gear Ratio and MPH/1000 rpm from the other data sheets as it does not contribute to the data that most owners are interested in.

Transmission 6-speed manual
Final-drive ratio 4.11:1, limited slip
Gear Ratio Mph/1000 rpm Max test speed
I - 2.66 - 8.3 - 50 mph (6000 rpm)
II - 1.78 - 12.4 - 74 mph (6000 rpm)
III - 1.30 - 17.0 - 102 mph (6000 rpm)
IV - 1.00 - 22.1 - 133 mph (6000 rpm)
V - 0.74 - 29.8 - 153 mph (5100 rpm)
VI - 0.50 - 44.2 - 153 mph (3500 rpm)

Okay, some quick conversions for 4.56 gears.
I - 44.5 mph @ 6000rpm
II - 65.9 mph @ 6000rpm
III - 90.8 mph @ 6000rpm
IV - 118.4 mph @ 6000rpm
V - 153 mph = 5726rpm (160.3 mph @ 6000rpm)
VI - 153 mph = 3930rpm (6000rpm in sixth? To damn fast)

For 4.88's
I - 41.4 @ 6000rpm
II - 61.3 @ 6000rpm
III - 84.4 @ 6000rpm
IV - 110.1 @ 6000rpm
V - 149.1 @ 6000rpm
VI - 220.2 @ 6000rpm

For 5.13's
I - 38.9 @ 6000rpm
II - 57.7 @ 6000rpm
III - 79.5 @ 6000rpm
IV - 103.6 @ 6000rpm
V - 140.3 @ 6000rpm
VI - 207.2 @ 6000rpm

For 5.38's
I - 36.5 @ 6000rpm
II - 54.1 @ 6000rpm
III - 74.5 @ 6000rpm
IV - 97.1 @ 6000rpm
V - 131.5 @ 6000rpm
VI - 194.2 @ 6000rpm

Last edited by Silverback; 02-08-2006 at 05:18 PM.
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post #2 of 34 Old 10-16-2005, 04:45 PM
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Silverback, There is another thread about guys only hitting 4th gear in the 1/4 mile. What would be the optimum gear the run at the dragstrip while hitting 5th gear thru the traps at 6000 rpm. Would this not be your best bet for 1/4 mile times.

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post #3 of 34 Old 10-16-2005, 06:17 PM
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Question

What can you do with an automatic? Can you change the gears in those? If so, how will the shifting be and how will it affect everything?
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post #4 of 34 Old 10-16-2005, 06:22 PM Thread Starter
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Quote:
Originally Posted by hemi killer
Silverback, There is another thread about guys only hitting 4th gear in the 1/4 mile. What would be the optimum gear the run at the dragstrip while hitting 5th gear thru the traps at 6000 rpm. Would this not be your best bet for 1/4 mile times.
Honest, I'm not trying to dance around giving you an answer, but there is no one answer for that question. Two major factors have to be addressed to answer that question. First is engine modification or horsepower you are producing. This will affect your acceleration numbers. The faster you accelerate, the more gear you need to acheive the trap speeds. Also it does not matter how much HP you can produce if you cannot put it to the ground, which leads us to the second item which is traction. The speeds that I listed are based on the diameter of the stock 305/40/22 tire. Current the only drag radial that we can run fits on an 18 inch wheel. Needless to say the rolling diameter of this tire is considerably less than the stock tire. This difference greatly affects the effective gear ratio. I have not checked the diameter of the 18 DR but let me make an assumption that it is only 80% of the circumfernce of the stock tire. For this example I'm going to use the 4.56 rearend in 4th gear. Stock you are going 118.4 mph at redline. With the DR's you are only going 94.7 mph.

I know this is probably more info than you need, but I hope that helps explain why there is not a simple answer to your question.
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post #5 of 34 Old 10-16-2005, 06:30 PM Thread Starter
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Quote:
Originally Posted by H-D
What can you do with an automatic? Can you change the gears in those? If so, how will the shifting be and how will it affect everything?
The automatic, like the 6 speed manual gear ratios are pretty much set unless you want to completely replace the majority of the internal parts.

With the manual you have to change out all the gears to change the ratios. Also I'm not sure if optional gearing is available or if you would have to have them manufactured special. In all honesty I'm suffering from a brain fart regarding how the automatic functions in regard to the ratios. You have the clutch packs that engage and disengage which is how it shifts and you have the planitary and sun gears, but I know there is more to it than that. Maybe someone can chime in and jog my memory.

Sorry I could not be of more help on this one.
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post #6 of 34 Old 10-16-2005, 07:35 PM
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Quote:
Originally Posted by hemi killer
Silverback, There is another thread about guys only hitting 4th gear in the 1/4 mile. What would be the optimum gear the run at the dragstrip while hitting 5th gear thru the traps at 6000 rpm. Would this not be your best bet for 1/4 mile times.
I was thinking the opposite. Shifting takes time and momentum. I would rather be able to hit the traps while still in 3rd, provided the truck is still pulling hard and still accelerating. Assuming I could generate enough trap speed, of course (which it sounds like I could not ).
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post #7 of 34 Old 10-16-2005, 10:03 PM
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These are the gear ratios for the tranny per the 2004 manual (probably the same for the 05's)...

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

Also, if you wanna play around on your own, and figure out different stuff for your project - try this link it is pretty cool ...

http://www.gounitrax.com/main.html and click on gearing formulas

have fun, if ya really wanna get out of the gate quickly - ditch the aluminum flywheel (unless you are road racing), and get a heavy steel one (75 lbs. or so) - stored torque is a wonderful thing.....


.... GOTTA GO TEXAS RANGER IS ON SEEE YA!!!! (Wifey )


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by/wifeypoo (typist)

Last edited by Includemeout; 10-16-2005 at 10:06 PM.
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post #8 of 34 Old 10-17-2005, 04:53 AM Thread Starter
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Quote:
Originally Posted by DarkSyde
Tim's right.

Less time in between gears is a good thing. For example, back in my F-body days, guys would actually run 4.10's with bolt-ons, up until they were trapping ~115 (redline in fourth). When they went into the motor, FI, juice, et all, we'd go back to 3.73's, and in some cases, a few peeps went back to 3.42's (not me ) as to not cross the line in 5th (which is more or less, and overdrive gear, even with a 6-speed)

Rowing gears costs you time. If you cross the line redline in fourth, or cross the line at 4800rpms in fifth, the truck still in fourth wins the race, given RT, launch, power, and everything else are equal.

Now, to the other side of the coin...

One thing to think about, a higher (numerical) *read, shorter gears* vehicle can often times break the tires loose easier than one with taller gears. The misconception is, that you'll spin more with 4.56's than one would with 4.10's. While it is easier to break loose in 4.56's, it is also easier to regain traction with closer gear ratios. Dont ask me why. For a more technical answer to this, I would call on the SilverBack, I bet he could tell us why this is (inertia vs. drag) in engineering terms.

Hope this helps
TJ
The simplest answer is the lower gears are not as throttle sensitive, or another way of putting it is that it takes more throttle to gain 5 mph with the lower gears. Make sense?
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post #9 of 34 Old 10-17-2005, 08:07 AM
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speed in gears

I do not know if I AM READING THAT RIGHT BUT,lower gears-higher number more throttle reponse,lower number less response,the whole idea is with lower gears you are in the power band sooner,more often,this does not mean that lower gears are always going to be the fastest,but driveability for me, it is the only way to go,many things have to be factered in when drag racing,hope this makes sence.
Bill

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post #10 of 34 Old 10-17-2005, 09:35 AM Thread Starter
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Quote:
Originally Posted by gearheadbill
I do not know if I AM READING THAT RIGHT BUT,lower gears-higher number more throttle reponse,lower number less response,the whole idea is with lower gears you are in the power band sooner,more often,this does not mean that lower gears are always going to be the fastest,but driveability for me, it is the only way to go,many things have to be factered in when drag racing,hope this makes sence.
Bill
In my response I said "Throttle Sensitive", not Throttle response. Let's see if I can explain it better.

For this explaination I'm just pulling numbers out of my ass, but the theory will apply non the less.

Okay, we take off from the line and start to spin the tires. So we feather the throttle and then give it half throttle. With the higher gears (4.11) this equals a wheel speed of 30mph. With the lower gears (4.56) it equals a wheel speed of 25mph. This is why I said throttle sensitive in response to DarkSyde's original question. You would not be attempting to spin the tires as fast, which makes recovery easier.

Did that help?
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