so i have a chance to pick up both front and rear carriers with 5.12 gears installed for a pretty cheap price.  my question is this, I have 31/10.5s on my samurai with stock gears and the 1.3L.  it is my daily driver and sees a bit of the highway, not much, but enough that it gets rather annoying topping out at 50-55 in 5th gear.  would 5.12 gearing be too low for highway driving or would it match up nicely with my tires? 

What do you have in there now?

i said i have the stock gears... so 3.73's i believe.

Can you even use 5th year now? I would think the 5.12 would work good!

If your wound up tight in 5th with 31" tires at 50-55 mph. You are allready re geard somewhere.....
 Are you sure that you know the correct history of your Zuke?
.....Boxcar...

5.12 gears and 31" tires =  15% change over stock.
3.73 gears and 31" tires =  -16% change over stock
here is a great table to get his info from :
http://www.lepayne.com/gears.html

here is a great online calculator for playing with gearing :
http://www.grimmjeeper.com/gears.html
Keep in mind a gearing calculator will NOT take into account the available (or lack of) hp of the engine.

- stock t-case and 3.73 R&P and 31" tires should have you spinning around 2500rpm at 55mph.
  with a low range crawl ratio of 30:1

- stock t-case and 5.12 R&P and 31" tires should have you spinning around 3450rpm at 55mph.
  with a low range crawl ratio of 42:1

- GRSII t-case and 3.73 R&P and 31" tires should have you spinning around 2950rpm at 55mph
  with a low range crawl ratio of 66:1

Not sure if you also run your Sami off road but if you do plan on dirving both on and off road, I would avoid 5.12 R&P gears.
I tried 5.12 R&P, stock t-case, and 31" tires... and they are just geared too low to also do the t-case (to get a good low range crawl ratio) for a dual purpose setup.
I would run the GRSII tcase with stock R&P if it was mine and I wanted to run the highway and have a decent low range crawl.

_

...  I would run the GRSII tcase with stock R&P if it was mine and I wanted to run the highway and have a decent low range crawl. _

X2. He said it!
True 31" tires are about 18% oversize (stock 205/70R15s are around 26.3"). Most are slightly less. Assuming Suzuki engineers got gearing about right, you'll need to make up about that amount in additional reduction, a combination of T-case and R&P gearing in high-range for the highway.  The additional reduction of a 4:1 low-range T-case is great for off-road, once you get the high-range about right.  The two 4.9:1 T-case gearsets available offer 16% & 18% additional reduction, with the Petroworks GRSII (18%) being a slightly better choice for 31s, IMHO.  Greater than 31s, most Zukers add additional reduction in the R&P gears, reducing drivetrain stresses.  With increasing tire size, eventually the rear axles become a weak link. When you put all the reduction in the T-case, you also should consider augmenting the T-case mounting, as it's a common problem area (as evidenced by all the mounting schemes available). The TrailTough Mighty Kong and ZOR's Snatch are popular.  With smaller tires, you may be OK by simply having your stock mounting arms reinforced.  I'm on 29's and had mine "strengthened" by Petroworks (for around $30 each).

Just because I like graphs, don't have anything to add to the discussion. 

Here is a stock Sammy with 28" tires:
http://www.solemnwarning.net/transmission/?id=103

Here is your stock ratio's with the 3.89 and 31" tires:
http://www.solemnwarning.net/transmission/?id=102

Here is a set of 5.12 gears with 31" tires:
http://www.solemnwarning.net/transmission/?id=104

KJ-  yes i have a 5th gear, although its not much of one haha.  i usually accelerate to the speed i want in 4th and then shift to 5th and cruise.  and i guess my top speed with 5th is between 50-60, depending on wind speed .   i'm about to make a 180 mile trip that i didn't want to take 4 hours, but i have a feeling that it will end up being just that.   happen to find the carriers with the gears for 300 on craigslist in my local area, so thats why i was asking.  but i think i will go ahead and stick with stock gears for now and save up for the tcase upgrade.

It sounds like you need more ponys under the hood.

You could also try a set of gear out of an automatic. They are 4.62 I think.

It sounds like you need more ponys under the hood.
You could also try a set of gear out of an automatic. They are 4.62 I think.  

Yet another option...  
If you have the early transmission with the the higher 5th OD gear (lower numerically), 4.625 R&P gears (8/37) could be a good choice if you want to keep the OEM T-case gears.  You'd be about 5% lower through the gears (no problem) and get most (over 60%) of the benefit of the later 5th OD transmission gear. But with a low range of (only) 2.268:1, you'd not have the deep 4:1 low range ratio of the aftermarket T-case gearsets.  This could probably be OK if you don't do a lot of difficult slow-speed off-roading.   Changing R&P gears is a bit technical (both front and rear!), and you might want to get help from someone who has done it (correctly) before.  With the limited power of the OEM 1.3L engine, it's especially important to get the gearing right.

It sounds like you need more ponys under the hood.

not an option for me right now.  frankly i was just looking for a way to make my soon to be trip a little bit of a shorter drive timewise, however i'm just going to save and do a transfercase gear swap and upgrade the Tcase mount and fix my problem.  should only be another month and i will be able to do that.

frankly i was just looking for a way to make my soon to be trip a little bit of a shorter drive timewise

www.hertz.com  :