gear ratio...
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Posting Guru
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From: San Antonio, Texas
gear ratio...
Hey fellas, trying to figure my rear end ratio on my 82 bronco.
I marked the tire and driveshaft and spun the tire 1 rev and the driveshaft spun 1 1/2 revs.
I did this with 1 tire off the ground and I also jacked up the whole rear end and tried but only one tire spun again.
Thanks in advance.
I marked the tire and driveshaft and spun the tire 1 rev and the driveshaft spun 1 1/2 revs.
I did this with 1 tire off the ground and I also jacked up the whole rear end and tried but only one tire spun again.
Thanks in advance.
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3.50:1, when you lift only 1 wheel you have to spin it twice, the reason is the spiders walk around half way and the case only makes half a turn becuase the other wheel isn't turning.
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
It actually sounds like a 3.00:1 ratio.
If you take the number of revolutions that each rear tire makes over a period of time, say 100 miles, the number of times the carrier revolves will be an average of the two tires.
Breaking it down, if you spin one rear tire one time, and the other hasn't moved at all, then the carrier has spun 1/2 a revolution. (1+0/2)
So in order to get the effect of spinning both tires once, you have to spin one tire twice. From there you can figure your ratio.
If you take the number of revolutions that each rear tire makes over a period of time, say 100 miles, the number of times the carrier revolves will be an average of the two tires.
Breaking it down, if you spin one rear tire one time, and the other hasn't moved at all, then the carrier has spun 1/2 a revolution. (1+0/2)
So in order to get the effect of spinning both tires once, you have to spin one tire twice. From there you can figure your ratio.
Cargo Master
Joined: Aug 2004
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From: Lynnwood, WA
I assume you need to do this because there is no tag on the rear end. But you can also check the tag on the front differential since it should be the same, or very close.
When you count revolutions you should put up some markers and and turn the wheel(s) until the markers on the wheel and shaft all align up again -- that may require quite a few revolutions (i.e. 11 on wheel and 39 on shaft) but the result will usually be unambiguous and very precise.
When you count revolutions you should put up some markers and and turn the wheel(s) until the markers on the wheel and shaft all align up again -- that may require quite a few revolutions (i.e. 11 on wheel and 39 on shaft) but the result will usually be unambiguous and very precise.
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From: San Antonio, Texas
Well, all the tags are there and they say 3.00:1 as does the door tag, but this truck takes off the line better than my old 83 that had a 351w.
Im mechanically inclined but I cant do math to save my life.
Could you find a lame way to tell me how to get 3.00:1 from 2 tire revs and 3 driveshaft revs?
Maybe you already stated it and I just didnt see it or I just didnt understand it.
I have a friend that rebuilt his c6 in a bronco and he says with the shift kit he bought he was able to run the tranny in a low and high gear mode depending on how he setup the valvebody, maybe the last owner had this done.
Thanks all.
Im mechanically inclined but I cant do math to save my life.
Could you find a lame way to tell me how to get 3.00:1 from 2 tire revs and 3 driveshaft revs?
Maybe you already stated it and I just didnt see it or I just didnt understand it.
I have a friend that rebuilt his c6 in a bronco and he says with the shift kit he bought he was able to run the tranny in a low and high gear mode depending on how he setup the valvebody, maybe the last owner had this done.
Thanks all.
Last edited by BroncoRoadKill; Feb 15, 2006 at 06:02 PM.
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Posting Guru
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From: the side of a mountain
i have seen it on here before and it made sence to me but for the life of me i cant find a way to explain it espc right now with my brain being toast. the way i checked mine was jacking up the whole rear, marking a spot on the tire and drive shaft, spun the drive shaft and counted how many times it took to spin the tire once. you just got to make sure the front end is blocked becuase you have have it in neutral.
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Posting Guru
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From: San Antonio, Texas
I found some time to tumble it over in my head and I think I got it.
Well, tell me if I'm right, somebody.
by turning the tire twice your making the carrier make 1 full rev, cause of the spiders, so if the carrier makes 1 rev then the driveshaft makes 3 revs to every 1 carrier rev and hence 3:1 ratio. right?
I think what was confusing me was the fact that to make the carrier make 1 rev you had to spin the tire twice and then count it as 1 rev.
Well, tell me if I'm right, somebody.
by turning the tire twice your making the carrier make 1 full rev, cause of the spiders, so if the carrier makes 1 rev then the driveshaft makes 3 revs to every 1 carrier rev and hence 3:1 ratio. right?
I think what was confusing me was the fact that to make the carrier make 1 rev you had to spin the tire twice and then count it as 1 rev.
Last edited by BroncoRoadKill; Feb 15, 2006 at 07:11 PM.
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Originally Posted by 76 F-150 390FE
3.50:1, when you lift only 1 wheel you have to spin it twice, the reason is the spiders walk around half way and the case only makes half a turn becuase the other wheel isn't turning.
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From: San Antonio, Texas
Originally Posted by The SnoMan
3.08, 1.5 times 2 is 3 to 1 not 3.5 and ford does not have a 3 to 1 but they have a 3.08
Thanks for all the help fellas.
This would mean that when the owner last had the tranny rebuilt, he must have had a shift kit with the ability to run the tranny in a lower range. cause as I said, the truck has 33s and it takes off like it has 3.55s or 3.73s
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Originally Posted by 76 F-150 390FE
no ford does use 3:1 in the 9" rear which that year bronco would be, and also if you read what i said earlier i said my math was off.
broncoroadkill, YES that is it exactly.
broncoroadkill, YES that is it exactly.
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well if you look in my gallery under "other crap" and look at the axle codes chart you can see that ford never used 3.08 they used 3, 3.25, 3.5, 3.7 and 4.11. now dana use a 3.07 and a 3.54 but not ford and not in the 9".
