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Old 06-02-2011, 04:08 AM   #1 (permalink)
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Default reduction gears

i'm looking into a set of reduction gears and was wondering what every one else thinks of them and what are all the pro's and con's i already know the give you excellent rock climbing ability's
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Old 06-02-2011, 10:46 AM   #2 (permalink)
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Quote:
Originally Posted by lokdzuk View Post
i'm looking into a set of reduction gears and was wondering what every one else thinks of them and what are all the pro's and con's i already know the give you excellent rock climbing ability's
Everyone? Now that's a TALL order! Transfer-case gearsets are possibly the most popular discussion subject. For the Samurai, they are identified (named) by their low-range ratio, most commonly:
4.16:1, 4.89:1, 5.13:1, 6.5:1 and even 8:1, all with some high-range reduction as well, roughly 12-24%, depending on gearset.

T-case re-gearing is best regarded part of an overall gearing change to adapt to larger tires and your intended application. Low range in the OEM Samurai gearset is 2.268:1, but many folks want more pulling/climbing wheel torque, especially after installing larger tires. Using my rig as an example, I'm on 29" tires (+10% diameter) with a 4:16 T-case with 12% additional high-range reduction (closely matching my larger tires). For me, it's important to preserve 5th (OD) gearing for the highway. My application is (way too much) California freeway driving and desert 4WD trails with no real rock climbing. Your needs will be different.

Edit: Lower T-case gears add stress on the mounting arms from the reaction torque. The many solutions to frequent T-case mount bending and breakage indicate the magnitude of this issue. If you need a lot of reduction, it's generally considered best to change the Ring & Pinion gears as well, and not perform ALL the gear reduction in the T-case. With modest changes, say 4:1 T-case gears and a gentler driving style, you might do well enough with simple mounting arm strengthening, as offered by Petroworks (-- that was my choice).

Last edited by Merlin93; 06-03-2011 at 11:26 AM.
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Old 06-02-2011, 05:45 PM   #3 (permalink)
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T/C gear reduction really helped me do what my buddies in the 'j' crowd could do with the big engines ( 6 & 8 cyls). They are really inexpensive and can be installed with nominal tools and experience on the kitchen table if the significant other is not too close at hand.
There is another caution though...more torque in the T/C needs to be addressed. Heavy duty mounts or another cradle to hang it in. I used the 'Mighty Kong' and find it excellent as a skid plate/hanger/cradle.
I don't notice any loss and still use my 5th gear (overdrive?)
my 2 cents.
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Old 06-06-2011, 03:26 PM   #4 (permalink)
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Im needing to do the same thing because im going to 31's from 235's.Even my 235's caused me to loose most of 5th gear. Im thinking 4.89 at least from all ive been told thats what I need.I may do some trails but no crawling.Mine is on the hwy more than off..
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Old 06-06-2011, 04:17 PM   #5 (permalink)
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Here are a couple of gearing calculators.
Gear Ratio Calculator
Suzuki Samurai Gear Calculator

If you have any questions on how they work be sure to ask. Nothing worse than doing gears to only realize you should have done them differently... ask me how I know.

Gears ............. 4.16:1 / 4.89:1 / 4.9:1 / 5.14:1 / 6.4:1 / 6.5:1
Low Reduction ... 84% / 115% /115% / 127% / 181% / 187%
High Reduction .. 12% / 18% / 16% / 18.3% / 17% / 20%

I went with the Trail Tough 6.4 gears but had thought about the 4.89's. I wanted the least amount of high range reduction but yet still have a good crawl ratio for when I do get into the rocks. The 6.4's only reduce the high range by 17% but still reduce low range by 181%, so for me it was better all around than the 4.89's.
Here is how the math worked out for my setup w/ 4.30 r&p, 31" tires, and early transmission (using the links above):
4.89 t-case = 4025rpm @ 65mph / crawl ratio = 77:1
6.4 t-case = 3996rpm @ 65 mph / crawl ratio = 100:1
So with the lower crawl ratio and the same or less rpm at freeway speed, I was sold on the 6.4 and I am happy with it. I will probably go to a larger tire next time and that will drop my rpm a little bit more at freeway speed.
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Old 06-06-2011, 10:27 PM   #6 (permalink)
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Quote:
Originally Posted by KJ2837 View Post
Im going to 31's from 235's. Even my 235's caused me to lose most of 5th gear. Im thinking 4.89 .... I may do some trails but no crawling.Mine is on the hwy more than off..
True 31's (most aren't) are +18% over stock, so the 4.89 gearset fits nicely for getting your highway gearing back. If you have an early transmission with the tall 5th OD gearing you'll still be rowing the gearshift lever, common with Samurais.

Last edited by Merlin93; 06-07-2011 at 09:56 AM. Reason: spelling
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Old 06-07-2011, 12:40 AM   #7 (permalink)
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What he ^ said !!!
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Old 06-07-2011, 08:55 AM   #8 (permalink)
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Yea,the 4.89 seems to be what everyone has pointed me to.But Im just going to get the T-case complete from Petro Works because im having issues with my shifter popping out of gear in 4H.Plus,ive never replaced gears and Id hate to screw it up!!
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Old 06-07-2011, 10:13 AM   #9 (permalink)
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Quote:
Originally Posted by KJ2837 View Post
... Im just going to get the T-case complete from PetroWorks because im having issues with my shifter popping out of gear in 4H.Plus,ive never replaced gears and Id hate to screw it up!!
Petroworks will do good work for you. I drove there from L.A. a few days ago for a different issue. PW normally installs their split-H shifter, which gives you 2WD Lo with the original single shifter. If you ever plan on towing, you can select 2WD (true) neutral as well (I tow 5-10K miles/year all over creation, so this is important to me).
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Old 06-07-2011, 10:53 AM   #10 (permalink)
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Yep,thats why I want theirs...Its like $900 shipped so I have to wait on the funds...And Id like to do that before the 31's cause its bad enough now with 235"s,lol.
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