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Author Topic: what is 3.42 ratio rear axle?  (Read 3662 times)
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Bane
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« on: 06/26/04 01:58 PM »

I hear everyone talking about ratio axle and all this stuff..i have no idea what this is...can someone please explain everything to me about this axle stuff.
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cadboy1
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« Reply #1 on: 06/26/04 02:03 PM »

For every one revolutiuon of the tire, the driveshaft has to spin 3.42 times..Its that simple Shocked

The higher the ratio the better for towing and accelaration but bad for MPG dead
« Last Edit: 06/26/04 02:06 PM by cadboy1 » Logged

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« Reply #2 on: 06/26/04 02:51 PM »

For every one revolutiuon of the tire, the driveshaft has to spin 3.42 times..Its that simple Shocked

The higher the ratio the better for towing and accelaration but bad for MPG dead


   "numerically" higher ratios give you a lower gear.  for example...

   -3.42 = best gas mileage, decent towing, okay off the line power
   -3.73 = good gas mileage, better towing capability, good off the line
   -4.10 = lower gas mileage, best towing capability, best off the line

   depending on what you are looking for in your ride should determine what axle ratio you get.  another example...
   i have a '68 Tempest.  i have a high gear, or "numerically" lower ratio.  this number sucks for off the line power.  but with the gas it burns, and the cost of gas these days i am not mad.  the higher stall converter helps out some.  but, i am not into 1/4 mile racing so this is not an issue to me.  that's why i said ealier it depends on what you are going to use your rig for.  you build it for the way you are going to use it.  i am a cruiser.  not a street bruiser.
   although i would like to go at least 3.73 on the Tempest.  we'll see.  i forgot to mention that the "numerically" higher gear ratios give out to the "numerically" lower ones down the road; the engine winds out quicker with the "numerically" higher one; the other guy is still moving out with the "numerically" lower ratio.
« Last Edit: 06/26/04 03:15 PM by PUNISHER » Logged

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« Reply #3 on: 06/26/04 03:33 PM »

FWIW, while the 4.10 are undoubtly the "best" for power and towing capability, according to GM they give darn good fuel economy, possibly just as good if not better than the 3.73 (dunno about anything taller though).

The engine won't be "working" as much in town either.

From a GM bulletin on Silverados/Sierras and presumebly applicable to Avalanches as well.
Quote
GM Truck Sales Bulletin

Subject: Axle ratio Selection, Silverado / Sierra 1500 Series 4x4 Models

It is generally accepted that a higher numerical axle ratio, like 4.10:1, produces more torque multiplication for added trailer towing performance etc., but burns more fuel. However, engineering improvements made to GM's full size pickups now provide the best of both worlds - economy and performance.

The Vortec 5300 V8 engine has significantly improved air flow producing close to peak torque and good fuel efficiency over a very wide operation range from less than 2,000 rpm to over 4,000 rpm.

The electronically controlled 4 speed automatic transmission features a 0.70:1 overdrive gear and a torque converter clutch that locks up in both 3rd and 4th gears for improved fuel economy.

A 4.10 axle ratio provides more load moving torque and it takes some load off of the transmission as the truck accelerates, so it upshifts faster and the converter locks up sooner. Elimination of any torque converter action, with the clutch applied, reduces heat build-up in the transmission for improved efficiency and durability. With a 4.10 axle ratio, the transmission will shift into overdrive sooner and hold in overdrive better. In overdrive, the final drive ratio is only 2.87:1 (4.10 x .70), a very fuel-efficient gear ratio.

In overdrive, cruising at 60 miles per hour the engine speed, with standard P245/75R16 tires and a 3.73 axle ratio, will be approximately 1780 rpm.

In overdrive, at the same 60 miles per hour but with larger P265/75R16 tires and a 4.10 ratio, the engine speed will be about 1870 rpm - less than 100 rpm more.

Between 1700 and 1900 rpm, both the torque and horsepower development of the Vortec 5300 V8 is increasing so the slight engine speed increase with the 4.10 ratio produces the expected performance improvement without a noticable increase in fuel consumption. In fact, when operating close to the Gross Vehicle Weight Rating (GVWR), or trailer towing, you can expect the 4.10 ratio to actually provide a gain in fuel economy.
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Yakmar
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« Reply #4 on: 06/26/04 04:01 PM »

Quote
In fact, when operating close to the Gross Vehicle Weight Rating (GVWR), or trailer towing, you can expect the 4.10 ratio to actually provide a gain in fuel economy.

yes, when TOWING there may be better fuel economy, but for THOSE of us who DO NOT tow, the 3.73 gives better fuel economy.  

When driving at normal highway speeds of 100km/hr, my tach is not even as high as 1780rpm as stated in that quote.  

At higher speeds, due to fewer spins at a given speed as a 4.10 , there are LESS rpm, and therefore usually BETTER fuel economy  (once again, when NOT towing)
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« Reply #5 on: 06/26/04 08:24 PM »



yes, when TOWING there may be better fuel economy, but for THOSE of us who DO NOT tow, the 3.73 gives better fuel economy.  




   you got it.
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« Reply #6 on: 06/27/04 11:45 AM »

I love the comparison of engine RPM between the 3.73 and the 4.10 but with different sized tires.  Of course the RPMs are going to be similar...

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« Reply #7 on: 06/29/04 08:53 AM »

This makes me feel a little better since I have the 4.10's
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Desert Rat
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« Reply #8 on: 06/29/04 06:40 PM »


When driving at normal highway speeds of 100km/hr,

When did they start actually paving roads in Newfoundland?  
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« Reply #9 on: 06/29/04 07:47 PM »

I love the comparison of engine RPM between the 3.73 and the 4.10 but with different sized tires.  Of course the RPMs are going to be similar...
HAH! Never noticed that!
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