2008 Gear Ratio
02-17-2012, 05:03 PM
#1
Member
Thread Starter
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...
02-17-2012, 05:34 PM
#2
Senior Member
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.
02-17-2012, 05:36 PM
#3
Jerry
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.
02-17-2012, 05:42 PM
#4
Jerry
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
02-17-2012, 05:44 PM
#5
I Like Tires
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.
02-17-2012, 06:00 PM
#6
Jerry
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.
02-17-2012, 06:00 PM
#7
kanga2311 FISO
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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02-17-2012, 06:05 PM
#8
Member
Thread Starter
It used to be off till I bought an Edge, plugged in tire size and 3.73 gear ratio (stock) and it appears to have corrected itself. I think i put in 2700mm
02-17-2012, 06:51 PM
#10
Senior Member
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
