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Gear Ratios

Rear Gear Ratio

Gear Ratios

Postby lilmagoo1 [OP] » Aug 12 2011, 1:13pm

I have a question out there wondering a few things i guess. I have a 07 1500 5.3l new body style. What gear ratio is in the vehicle. what would happen if i changed the ratio, to a faster one, what would happen to a lower ratio? seems like the reason my mileage isnt the best. It seems like this because i had a dodge and when cruising down the highway it felt like it was in a higher gear or something seemed like it just had lower rpms going down the highway. this chevy seems almost like it needs another gear or something. wondering if gear ratio would help?
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Re: Gear Ratios

Postby Jim08SLE » Aug 12 2011, 1:34pm

Easiest way find out would be to look on the window sticker... :lol:

If that is not available to you... enter your VIN at http://www.compnine.com/vid.php

That should tell you more about your truck than you probably need to know.

As far as faster... well, that would depend on what you currently have. Best of luck!
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Re: Gear Ratios

Postby jocko463 » Aug 12 2011, 1:58pm

Look in the glovebox. There should be a decal in there with a bunch of cryptic numbers and letters ...those are the RPO codes for the options on your truck.

Get the VIN number and go here: http://www.compnine.com/vid.php

This is a comprehensive VIN decoder that not only lists all the options/RPO codes for the vehicle in question but will possibly also tell you when/where it was built and possibly provide a window sticker. Compare what you get as a result with the decal in the glovebox.

Oh, and your axle ratio will be among the RPO codes.

Final drive ratios are designated in mechanical and numerical terms ...and the two are opposite. So, for instance, a 4.11 rear end would be a high numerical ratio but a low mechanical one; a 2.73 would be a low numerical ratio but a high mechanical one.

If you are having mileage issues and the engine is running at a higher cruise RPM on the highway then swapping in a lower numerical/higher mechanical ratio will help in that department. What this new ratio will do is: reduce engine RPM for any given cruise conditions; reduce your acceleration rate; and, if you don't adjust for it, screw up your odometer and speedometer (since it is set to work with the existing final drive ratio). The reduced engine RPM is what will, theoretically, improve your mileage. You have to be careful not to raise the ratio too high or you'll kill acceleration and to compensate you'll push harder on the go pedal ergo negating some of the benefit of the taller final drive. It's all a compromise. Your truck may have had some heavy duty trailering package ....the VIN decoder will reveal that info ...and may be the reason for the high numerical final drive. Also, consider what you are going to use the truck for ...do you tow or plan on towing on a regular basis? If so, then be careful if you do replace the high numerical drive with a lower one.

My '06 has a trailering package and it's final drive is 3.23:1. That equates to about 1700-2000RPM in highway cruise. Real life mileage varies from 15-17mpg depending on the mix of highway vs local driving.
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Re: Gear Ratios

Postby lilmagoo1 [OP] » Aug 12 2011, 2:23pm

alright well i did that site and it was pretty cool man, it has 3.73 rear end in it.
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Re: Gear Ratios

Postby jocko463 » Aug 12 2011, 2:34pm

Well, there ya go ....3.73 is a little on the low side for everyday driving. Sounds like maybe it was part of a tow package or this guy liked to drag race ;-)
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Re: Gear Ratios

Postby lilmagoo1 [OP] » Aug 12 2011, 2:56pm

thats even what the vin # says came stock, my old 5 speed have 373 rear end in it and it ran like a raped ape
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: 18" MBmotoring V-drive rims W/ 00 offset :
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Re: Gear Ratios

Postby Jim08SLE » Aug 12 2011, 2:56pm

I like my 3.73... :twisted:
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Re: Gear Ratios

Postby Chasmanian » Aug 12 2011, 5:35pm

What do you have on your truck for tires? Stock? Taller tire than stock?
I know when my truck was stock it got way better mpg than with the lift and bigger tires. I also have 3.73 gears. Truck still has good power but does kick down a gear in the hills more than when stock. The tuner helped quite a bit, you may want to look into one.
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Re: Gear Ratios

Postby lilmagoo1 [OP] » Aug 12 2011, 5:59pm

i run a 285/70/18 bfg all terrain. ive had lifted trucks but they were all manual. i know bigger tires makes less gas milage takes more muscle to spin em and more rev for a full rotation of the tire.
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: 07.5 Silverado : 3"lift & 1.25" body lift : 295/70R18 Trail Grapplers :
: 18" MBmotoring V-drive rims W/ 00 offset :
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Extra Info: 5.3 L 4x4
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Re: Gear Ratios

Postby DRK4X4 » Aug 12 2011, 8:33pm

3:73 is my favorite gear to have, it pulls good and has some take-off power. My 04 Z71 x cab had 3:73 with the 5.3/ 4 spd auto and it got much better gas mileage than my 11 reg cab with the 4.8 /4 spd auto. I think my 11 has 3:42 gears and it makes the truck feel sluggish to me on take-off.
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