Calculating diff ratio!
Thread Starter
Pro
Joined: Mar 2001
Posts: 573
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From: Gold Coast Queensland Australia
Calculating diff ratio!
Hi Guys,
OK, I've read a few posts lately and searched a bunch of archives with no luck so I'll just have to ask the question.
I have a NON posi and have chocked one wheel to prevent rotation and have rotated the other wheel twice and the Driveshaft has rotated just over 3 and a quarter turns.
SO, if it turned 3 and a quarter turns I presume that it would be a ratio of 3.25 and if so as it has turned just over 3 and a quarter turns, would I be correct to assume that the ratio is 3.36 and would this be common on a NON posi unit?
Thanks for the help as usual, Mark.
OK, I've read a few posts lately and searched a bunch of archives with no luck so I'll just have to ask the question.
I have a NON posi and have chocked one wheel to prevent rotation and have rotated the other wheel twice and the Driveshaft has rotated just over 3 and a quarter turns.
SO, if it turned 3 and a quarter turns I presume that it would be a ratio of 3.25 and if so as it has turned just over 3 and a quarter turns, would I be correct to assume that the ratio is 3.36 and would this be common on a NON posi unit?
Thanks for the help as usual, Mark.
Le Mans Master
Joined: Jan 2002
Posts: 8,913
Likes: 283
Re: Calculating diff ratio! (59er)
Just spint the tire once!, note the revolutions of the driveshaft yoke. So if the tire moves one rev, count the revs of the yoke compared to the single tire rev. If the yoke turns around 3.25 times, it is most likely 3:36's. Depending on you tire size you could also note the half shaft yoke for one turn.
Mark
Mark
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
Re: Calculating diff ratio! (ghostrider20)
I believe you rotate the tire once and multiply driveshaft revolutions by two with an open rear end. That's with one wheel on the ground. With a posi, both wheels rotate one turn and read directly the driveshft rotation.
Yes, a 3.36 is a common '63 ratio whether open or posi.
Yes, a 3.36 is a common '63 ratio whether open or posi.
Race Director
Joined: Jan 2003
Posts: 17,682
Likes: 3,678
From: Central Arkansas
Re: Calculating diff ratio! (MikeM)
I think there is a problem in doing this with an open rear end because you don't know how much turn of the tire is translating into rotation of the pinion gear (driveshaft) and how much is translating into rotation of the pinion gears in the differential (opposite tire) unless you are real careful. Sometimes you will turn a tire and the other one will remain motionless for a while and then it will start rotating irregularly in the opposite direction. This gives a bad ratio calculation. If you can be sure that the tire you rotate in one direction, exactly matches the amont of rotation of the opposite side tire in the opposite direction, then multiplying by two should give you the right ratio. Good luck. :flag
Whoops! I just noticed where you said you chocked one wheel. That should work. Forget what I said above. Not awake yet :banghead: :banghead:
[Modified by DansYellow66, 3:50 PM 4/6/2003]
Whoops! I just noticed where you said you chocked one wheel. That should work. Forget what I said above. Not awake yet :banghead: :banghead:
[Modified by DansYellow66, 3:50 PM 4/6/2003]
