axle ratio |
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dodjh
Member Joined: 18 July 2012 Location: ms Status: Offline Points: 1325 |
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Posted: 25 Apr. 2015 at 1:24am |
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I've searched the site for posts on finding axle ratio and have come up short.
How do you determine axle ratio by counting rotations of wheel and drive shaft? Thanks |
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jpet
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1. Jack up rear tire (one side only)
2. Spin the wheel 2 times 3. Count revolutions of the drive shaft. That's your ratio Edited by jpet - 25 Apr. 2015 at 1:36am |
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CJ2A #29110 "General Willys"
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danover321
Member Joined: 30 May 2012 Location: Smithville, MO Status: Offline Points: 357 |
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If you have the standard CJ2a Dana 30 and Dana 41 you will have a 5:38 gear ratio. If you have the military Dana 27/23 you will have a 4:88 gear ratio.
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44 Willys MB 379XXX
45 Willys MB 459XXX 46 Willys CJ2A 38008 46 Willys CJ2A 38136 47 Willys CJ2A 97474 US Army Active/Reserve 1989 to 2005 Desert Storm, Bosnia, Kosovo, Iraq Invasion 2003 |
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Thorholt
Member Joined: 31 Mar. 2015 Location: MN Status: Offline Points: 52 |
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Put a mark on each rear tire on the inside of it so you can see it easily then mark the pinion the same way, then using both hands turn both rear tires exactly one turn in the same direction while counting how many times the pinion rotates, if the pinion turns about 4 and 1\4 turns you have 4.27 ratio, if it turns 5 and a 1\3 turn you have 5.38. It's not exact but will get you close on ratio. |
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dodjh
Member Joined: 18 July 2012 Location: ms Status: Offline Points: 1325 |
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It is the military Dana....so if I spin the rear tires 2 complete revolutions and the drive shaft spins 4 times, that would be a 4.88 ratio? |
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dodjh
Member Joined: 18 July 2012 Location: ms Status: Offline Points: 1325 |
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Okay, I marked D.S. and 1 rear tire that was off the ground. I spun the tire 2 complete revolutions and the D.S. spun 5 1/3 times. 5.38?
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dodjh
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Thorholt...I don't follow your method....do I remove the pumpkin cover to mark the pinion gear or mark the D.S. yoke on the outside?
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JeepFever
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Yes :) 5.38 |
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Thorholt
Member Joined: 31 Mar. 2015 Location: MN Status: Offline Points: 52 |
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Just make a mark on the yoke, drive shaft, what ever that is easy to mark, you just need that mark to count how many times the pinion turns. Spinning one tire might work on a Jeep but if you spin only one tire you are including the spider gears into the equation, they don't effect the actual ratio but they might give you a false ratio, do what you want, I am just giving you the easy way to do it
Edited by Thorholt - 25 Apr. 2015 at 9:09am |
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jpet
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With all due respect, This is incorrect . One tire is jacked up. One tire is solidly on the ground and can't turn. This is why you spin the wheel twice. Because the differentials distribute the power for both wheels to the one that is free spinning. Both wheels going down the road straight, is even distribution (1:1). When you make a turn, if the inside wheel is turning 33 percent slower, the ratio would be .5:1.5 inside to outside wheel. .... so when one wheel is held solid, all the drive is distributed to the spinning wheel (2:0) so in a nutshell, one wheel spun twice is equal to two wheels spun once.
No. That method requires you to jack both wheels up, spin both wheel in perfect sync, while trying to look at the driveshaft. If you jack one wheel up, and leave the other on the pavement, you can spin the wheel twice with one hand, not worry about trying to spin two wheel together equally, and never take your eyes off the drive shaft. Easier, safer, more accurate. To answer the original posters question, your ratio is 5.38 since you got 5-1/3 revolutions after spinning one wheel twice. The true ration is 5.375:1. If you want to do a dead nuts confirmation, jack up one wheel, put a timing mark on the drive shaft, spin the wheel 16 times. When you stop the drive shaft timing mark should be in time with the pointer because the drive shaft would have spun exactly 43 times. 5.375:1 = 43:8. Differential ratio (spinning wheel twice) = 2:0 Final ratio: 43:16 Edited by jpet - 26 Apr. 2015 at 12:57pm |
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CJ2A #29110 "General Willys"
MB #204827 "BAM BAM" "We do what we can, and we try what we can't" |
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52 M38
Member Joined: 26 Nov. 2012 Location: New England Status: Offline Points: 1286 |
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And in our next episode JPet will explain the equations behind Eistein-Rosen Bridge Wormhole theory and how that relates to twin stick D18 warp drives.
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rocketeer
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When someone says "military" they mean a WWII full floater. Is that what you have? Larry |
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jpet
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.... I suppose I should add then that if you jack up one wheel, spin it 16 times and the drive shaft makes exactly 39 revolutions, you have a 4.88 ratio or actually 4.875:1
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CJ2A #29110 "General Willys"
MB #204827 "BAM BAM" "We do what we can, and we try what we can't" |
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dodjh
Member Joined: 18 July 2012 Location: ms Status: Offline Points: 1325 |
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rocketeer, it is a post WWII Jeep....'53'.
jpet, thank you for your post. JeepFever, thank you for your post. Thorholt,thank you for your advice. |
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"COURAGE IS BEING SCARED TO DEATH
-BUT SADDLING UP ANYWAY" JOHN WAYNE |
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danover321
Member Joined: 30 May 2012 Location: Smithville, MO Status: Offline Points: 357 |
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Did the early CJ2a's with the full floating axle have 4:88 or 5:38? I had the belief they were 4:88 until the production change to the Dana 41.
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44 Willys MB 379XXX
45 Willys MB 459XXX 46 Willys CJ2A 38008 46 Willys CJ2A 38136 47 Willys CJ2A 97474 US Army Active/Reserve 1989 to 2005 Desert Storm, Bosnia, Kosovo, Iraq Invasion 2003 |
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autolite
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All came with 5:38's. Only WWII M.B./GPW came with 4:88.
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willys jeep
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danover321
Member Joined: 30 May 2012 Location: Smithville, MO Status: Offline Points: 357 |
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My eyes have been opened! Thanks, Dan |
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44 Willys MB 379XXX
45 Willys MB 459XXX 46 Willys CJ2A 38008 46 Willys CJ2A 38136 47 Willys CJ2A 97474 US Army Active/Reserve 1989 to 2005 Desert Storm, Bosnia, Kosovo, Iraq Invasion 2003 |
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dodjh
Member Joined: 18 July 2012 Location: ms Status: Offline Points: 1325 |
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If I jack up one rear tire, put trans. and T/C in neutral, mark drive shaft and tire, after one revolution the DS spins 2 1/3 revolutions.
If I spin the tire 2 revolutions the DS spins 5 1/4 revolutions. What is my axle ratio? Thanks |
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"COURAGE IS BEING SCARED TO DEATH
-BUT SADDLING UP ANYWAY" JOHN WAYNE |
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