2008 Gear Ratio
Thread Starter
Member
Joined: Feb 2011
Posts: 77
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From: League City, Texas
2008 Gear Ratio
I bought my truck used with its lift and tires already on it. Is there a way for me to check the gear ratio and see if the previous owner changed them from factory? I know about reading the axel tag, door jam, blah blah...but if it was changed from factory then those id# would be wrong...
Senior Member
Joined: Dec 2010
Posts: 260
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From: Texas
Unless u got paperwork or was told from the pervious owner what aftermarket gears were installed, there's no way to tell unless u open the housing up. I could be wrong but that seems to be the only way.
Jerry
Joined: Oct 2011
Posts: 1,473
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From: meridian, idaho
What size tires do you have and what are your rpms at different speeds? Say at 60,65,70 and 75. There are charts online that tell u what your rpms will be at certain speeds depending on what gears u have. Also decide if u are going to do a speed test with or without overdrive.
Jerry
Joined: Oct 2011
Posts: 1,473
Likes: 32
From: meridian, idaho
Like this one. U will have to put in different gear ratios to see which one matches the data u gather from speed and rpm. 3.55, 3.73, 4.10 or 4.56. It figures out rpm at different speeds with whatever gears u put in, so if u just change them up one should come close to your data and u can figure out what u have.
http://www.ringpinion.com/Calculators/Calc_RPM.aspx
http://www.ringpinion.com/Calculators/Calc_RPM.aspx
I Like Tires
Joined: Aug 2010
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From: Texas
Originally Posted by jerrybizzle
What size tires do you have and what are your rpms at different speeds? Say at 60,65,70 and 75. There are charts online that tell u what your rpms will be at certain speeds depending on what gears u have. Also decide if u are going to do a speed test with or without overdrive.
Not to be harsh OP but these are questions that should have been asked before you purchased the truck. Your best bet is to call the last owner up again and ask him if he ever re-calibrated the speedometer and if he changed the gear ratio.
Jerry
Joined: Oct 2011
Posts: 1,473
Likes: 32
From: meridian, idaho
This would also be assuming his speedometer has been re-calibrated.
Not to be harsh OP but these are questions that should have been asked before you purchased the truck. Your best bet is to call the last owner up again and ask him if he ever re-calibrated the speedometer and if he changed the gear ratio.
Not to be harsh OP but these are questions that should have been asked before you purchased the truck. Your best bet is to call the last owner up again and ask him if he ever re-calibrated the speedometer and if he changed the gear ratio.
kanga2311 FISO
Joined: Apr 2009
Posts: 201
Likes: 12
From: Viroqua, WI
You could check the speedometer with a gps system(Garmin, tom tom), or possibly with a smartphone. There is probably an app for that. I like the GPS because even from factory, the speed is off 2 or 3 MPH. But I guess as the tires wear, the speedo becomes a little off.
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Joined: Apr 2011
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From: Bucks County Pa.
http://www.jedi.com/obiwan/jeep/misc/gearratio.html Look here -lift the truck off the ground and ....well you'll get it
Senior Member
Joined: Sep 2007
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From: Las Vegas
Jack the rear end up. Spin the rear tires one full rotation. Count the number of times the drives shaft spins. If it spins about 3.75 Times you have 3.73. If it spins 4.5 Times then you have 4.56
You get the idea. Tranny must be in neutral
You get the idea. Tranny must be in neutral