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post #1 of (permalink) Old 01-22-2001, 08:49 PM Thread Starter
 
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Gear ratio program.How do you figure final ratio?

My friend is going to make me a program where you can put your gear ratios in and then it will tell you your final crawl ratio...
What all ratios would I need to know..Anyone know the formula?I saw it in the back of a 4Wheeler a while back

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post #2 of (permalink) Old 01-22-2001, 09:51 PM
 
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Re: Gear ratio program.How do you figure final ratio?

You multiply your axle gear ratio x your 1st gear tranny ratio x your low range T case ratio.
For example when I was running an NP 435 in my YJ it was.
4.56:1 axle
4.0:1 T case(Tera Low kit)
6.69:1 NP 435 Tranny
for an overall ratio of about 122:1(no calculator).
If you have a secondary or stacked T case that would be multiplied also.
For example my new drive train will be.
4.56:1 axle
6.69:1 Tranny
2.47:1 D20 secondary T case
3.70:1 D20 Primary T case
I dont know what that works out too, but you just need to multiply them all together.
Is that about as clear as mud??


Jeff
89 YJ
There is no "TRY", Just "DO" or "DONT DO"
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post #3 of (permalink) Old 01-23-2001, 12:41 PM
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Re: Gear ratio program.How do you figure final ratio?

If your buddy was slick, he would have the program just put in the #'s for the people by choosing the features they have, off-road.com's tech section has tranny first gear info & t-case info.

Me, I had a really sad 19:1 crawl ratio with my stock 999 Auto (2.74:1 - 1st gear) Dana 300 t-case (2.6:1 low range) & 2.73 gears = 2.74 x 2.6 x 2.73 = 19.45 It will increase to around 41:1 when as soon as I put my 3.73 gears & Tera-low kit in.

Jeffs 279:1 crawl ratio is amazing considering that is 14 times slower than a stock 1985 CJ's! Even older 1970's CJ5's with 3.73 stock gears only had a 23:1 crawl ratio (2.99 1st gear T-150, 2.06 D-20 low range & 3.73 gears) Jeffs gears are still 12 times slower!

-Mel

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post #4 of (permalink) Old 01-23-2001, 08:21 PM
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Re: Gear ratio program.How do you figure final ratio?

http://www.dirtroad.com/gears.htm

Try this program!
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post #5 of (permalink) Old 01-23-2001, 08:48 PM
 
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Re: Gear ratio program.How do you figure final ratio?

Jeff-
There's such a thing as 'too low'.
.. unless ya like shifting on the top of every rock...
Even auto trannees skip a beat on shift, the difference of a climb ... or slide.
Mark my words.

JAF
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post #6 of (permalink) Old 01-23-2001, 08:57 PM Thread Starter
 
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Re: Gear ratio program.How do you figure final ratio?

Thanks guys..Damn I didn't know there was already a program out!I wonder what mine is......

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post #7 of (permalink) Old 01-23-2001, 09:19 PM
 
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Re: Gear ratio program.How do you figure final ratio?

Jaffer,
If there is such a thing as too low I dont know how low it would be. I can always shift out of either one of the T cases or up a gera to get where I need.
BUT, I got to drive a wrangler with 210:1 gear ratio, up a rock face that I always fight to get up, its ability to keep slowly grabbing its way forward without ever breaking away was wild. Very impressive to say the least. i deffinitely wouldnt pre judge super low gear ratios with out dated misconceptions until you give it a try, it is awsome. A freind in the club Ive joined in Ridgecrest has climbed 6 of the 7 waterfalls heading up Surprise canyon using his 200:1 Wrangler, previousely only 4 were considered climbable. If you have ever watched the well prepped Marlin set ups in Toyotas, in action, you really cant argue with their climbing prowess either.
But the versatility is really what I like about stacked T cases, rather than going to one low 4.3 t case and being stuck with that I can have the ability to use a 3.7, 2.5, or a combo of both, all with gear driven Iron reliability. Really dont see any down side.

Jeff
89 YJ
There is no "TRY", Just "DO" or "DONT DO"
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