What gear am I running?
#1
04-20-2004, 03:43 PM
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What gear am I running?
I have looked through some of the threads concerning rear end ratios and pretty much have figured that my 90 Bronco should be a 3.55 stock ratio. However, my RPM's at 65 mph are no where near what it should be and I am wondering if I have an off the wall ratio. At 65 mph I am running about 1750-1800 rpm's. I have 31 in tires. Anyone have any idea what the rearend might be???? Thanks in advanced.
#2
04-20-2004, 04:00 PM
Check out http://www.4lo.com/ I just punched in some of the numbers you provided (and I assumed AOD, but you didnt tell us), and got 3.71 for gearing at 1750rpms. So....by that logic, 3.73s sound right. You might want to mess around on that site, and see what you can determine. Another way to "eyeball" it is to see how many rotations of the driveshaft (approx) there are for 1 revolution of the tire (<--safety comes first here!). That number should indicate what you have for gearing.
Rich
Rich
#3
04-20-2004, 08:00 PM
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Hey, I've got family in Chillicothe! Anyhow, the numbers on that site are not accurate, at least for me. Knowing what I have already, I tried their formulas, and the numbers were way off.
The lower the gear you go (numerically higher), the faster the engine has to turn to spin the tires, right? So if you have 3.73s your rpm will be higher. The higher the gear you go (numerically lower) the slower the engine has to turn. There is a metal tag on one of the cover bolts on the rear end (or at least there should be) that will tell you what your ratio is, and there should be a sticker on the front end that shows as well.
This is a little more accurate:
http://www.samsoffroad.com/samsoffro...RatioGuide.htm
In fact, just do this: gear ratio = rpm x tire diameter, Divided by- mph x 336
This is from the Four Wheeler magazine archives
I bet that was the standard ratio for that year from the factory. Who knows.
The lower the gear you go (numerically higher), the faster the engine has to turn to spin the tires, right? So if you have 3.73s your rpm will be higher. The higher the gear you go (numerically lower) the slower the engine has to turn. There is a metal tag on one of the cover bolts on the rear end (or at least there should be) that will tell you what your ratio is, and there should be a sticker on the front end that shows as well.
This is a little more accurate:
http://www.samsoffroad.com/samsoffro...RatioGuide.htm
In fact, just do this: gear ratio = rpm x tire diameter, Divided by- mph x 336
This is from the Four Wheeler magazine archives
I bet that was the standard ratio for that year from the factory. Who knows.
Last edited by threefiftyone; 04-20-2004 at 08:03 PM.
#5
04-21-2004, 10:00 AM
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Originally Posted by threefiftyone
Hey, I've got family in Chillicothe! Anyhow, the numbers on that site are not accurate, at least for me. Knowing what I have already, I tried their formulas, and the numbers were way off.
The lower the gear you go (numerically higher), the faster the engine has to turn to spin the tires, right? So if you have 3.73s your rpm will be higher. The higher the gear you go (numerically lower) the slower the engine has to turn. There is a metal tag on one of the cover bolts on the rear end (or at least there should be) that will tell you what your ratio is, and there should be a sticker on the front end that shows as well.
This is a little more accurate:
http://www.samsoffroad.com/samsoffroadsto/GearRatioGuide.htm
In fact, just do this: gear ratio = rpm x tire diameter, Divided by- mph x 336
This is from the Four Wheeler magazine archives
I bet that was the standard ratio for that year from the factory. Who knows.
The lower the gear you go (numerically higher), the faster the engine has to turn to spin the tires, right? So if you have 3.73s your rpm will be higher. The higher the gear you go (numerically lower) the slower the engine has to turn. There is a metal tag on one of the cover bolts on the rear end (or at least there should be) that will tell you what your ratio is, and there should be a sticker on the front end that shows as well.
This is a little more accurate:
http://www.samsoffroad.com/samsoffroadsto/GearRatioGuide.htm
In fact, just do this: gear ratio = rpm x tire diameter, Divided by- mph x 336
This is from the Four Wheeler magazine archives
I bet that was the standard ratio for that year from the factory. Who knows.
#6
04-21-2004, 11:42 AM
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I got 3.07 (1800x31, divided by 65x336) Actually its 28844[3.07] I don't know man, I thought there was a guide on this site that converted the axle codes on the door frame to what they mean. Try the driveshaft theory. Hope I could help
Last edited by threefiftyone; 04-21-2004 at 11:46 AM.