To try and review, the SOTF has problems.  Mostly IN the front differential. 
http://www.zukiworld.com/forum/index.php?topic=21016.0
http://www.zukiworld.com/forum/index.php?topic=20825.0
Replacement of the front differential and removal of the air SOTF seems to be favoured by many.
http://www.zukiworld.com/month_030104/feature_tsb_shiftontheflyremoval.htm
Though for a daily driver, these opinions seem to gray a bit.

I'm hoping to keep the SOTF (daily driver, and my wife would hate manual hubs).  I've ordered a new actuator, and some new bearings and seals since it'll be open.  The parts so far a close to $400cdn.  I'll try and take pics and document the time and $$ (I'm not a mechanic so 1hr for me shouldn't be more then an hour for anyone with sense).

I tow a small camper and would like to get 31-32" tires soon.  I need to know more about re-gearing, specially the cost and where.  I have a '99, 2L, Convertable, and I'm not sure of the gearing.  I see this was looked at last year.
http://www.zukiworld.com/forum/index.php?topic=18779.msg159793;topicseen#msg159793

Info and opinions would be great before I get to far. 

According to this

http://bbs.zuwharrie.com/content/topic,18763.0.html you have 4.625 in your diffs.

Stock tires (235/60-R16) are about 27".

To restore the overall gearing with 31" tires, you need 4.625*31/27 = 5.310

The nearest to that, from:

http://bbs.zuwharrie.com/content/topic,15579.0.html is 5.38, but that's said to be rare, so you may have to settle for 5.125.

The "right" tires for 5.125 are 5.125/4.625*27 = about 30"

i'm currently running 4.62's on my 2003 zr2 2door 2.0L, running 31x9.5 swamper radials.  i have no real power issues other than on the highway running 5th gear uphills or into really strong wind.  i imagine if i were pulling a little trailer it would be getting weak though.  also occasionally on rocky terrain i wouldn't mind being geared a little lower but i don't know how much difference the diff gears would really make.  anybody done this swap want to clear this up?  also how much better does the gas mileage get?  i was getting almost 500km per tank when new, now i'm getting more like 400 and a bit km per tank.

I'm running 5.12s in my GV with 31s.  Not much over the stock 4.88s, but every bit helps.

Thanks for the response so far..

Soooo, if I was to do the gear swap I'm guessing that the rings are interchangable.  Do I also need to change the pinion??  Would it be difficult or not worth it to check the auto wreckers, or should I buy new??

I have have not done much off roading yet, I just don't wont to later wish I had done the swap when I had a chance.

Soooo, if I was to do the gear swap I'm guessing that the rings are interchangable.  Do I also need to change the pinion??

Ring and pinion are a matched set - no mixing between ratios.

Ring and pinion work should be done by a pro.  It requires a very precise setup.  Good luck.

Get the front and rear 3rd members complete from a 96-98 sidekick with either manual or 4spd auto 1.6L 16V and they *should* be 5.12's, that way you won't have to set up any R&Ps, just bolt them in (and do the rest of the SOTF elimination)

Can't seem to find a front and rear diff from a '96-'98.  The sidekicks seem to be slowly dissapearing form the wreckers.

Did get a line on a '99 front and rear diff for not that much $$$.  I'm told no air leaks, I'm going to check with him again that I mean IN THE DIFF, not the pump.  They have the 5.125 gearing.

I'm thinking of just swaping the diff's.  Hopefully I'll have my 4wd back and lower gears.  If not, I HAVE LOWER GEARS and still need to fix the front diff OR swap it out.

Later, if I have the air leak in the diff again.  Do I have to stick with the Front Diff from a '96-'98 if I have a mechanic swap out the R&P.  Is the 26 spline (on the Pinion's transfere case side, right?) on the 96-98 front diff the ONLY reason that the swap must be done with those???  Using an easier to find (cheaper?) diff and swaping the R&P would be a good excuse for having lockers installed. 

Thanks for everyones input, I've learned that R&P setup is for those with way more experience then myself.

The reason I said 96-98 is that is the only years that Sidekicks came with 26 spline sidegears, which is the spline count (and axle size) you currently have.  Earlier years are 22 spline and smaller axles.

I know I'm dragging my feet with doing this.  I hate spending money and I get worried about doing the wrong thing.  
I thought I had a line on a front and rear diff of a '99 with 5.13 gears, but no luck.

Still planning to swap out the front and rear 3rd member (no R&P setup concerns) with something with 5.13 gears and keeping the SOTF.  Hopefully the front 3rd wont have the air leak problem (yet?) and I've ordered some manual hubs to install after the fix.  The hubs should help decrease wear and hopefully the chance of air leak problem.

Now looking at front and rear differentials from a 2002 XL7 auto (5.13 gears).  Only concern is will they fit?? 
-Are the XL7 '01 to '05 the same as the GV's and Vitara's (pretty sure but gotta ask)??
-Does the rear carrier use 8 bolts to attach to the axle??
-Does the front Carrier use the same mounting bracket to attach to the cross member??
-Is the XL7's front Axle the same as the Vitara's (except hopefully steel)??

Hopefully this will be all yes, yes, yes, and yes, with a bonus yes for the steel axle.  If this works out, I'm wasting no more time worrying about right parts and trying to find the cheapest price.

The XL-7 rear is pretty much totally different.  No parts cross-reference with your truck (your driveshaft won't even bolt up to it), and there are no known locker/lsd upgrade options for it.  Walk away.

Thanks.
I just took a peek in the XL7 forum.  I don't need that type of stress and "McGivering". 

5.13's are hard to find in 99 and later. I think I found a rear from 99 vitara with 5.13, but no front.
Would the front diff from the XL7 still fit in??  I'm guessing so since the SOTF removal article included XL7 as well.  I know I can get an XL7 front.

Thanks for the quick reply. 

Would the front diff from the XL7 still fit in??  I'm guessing so since the SOTF removal article included XL7 as well.  I know I can get an XL7 front.

Thanks for the quick reply. 

The Front XL diff will bolt in, provided you get the mount with it.  Otherwise, it won't.  The steel housing are stronger than the aluminum ones, BTW.

I noticed you said you are getting manual hubs to eliminate the wear.  Great idea, but you might as well do the SOTF elimination at the same time, since you have to lock the hubs anyway.  Even with a Kick open diff, as long as the hubs are locked, you can SOTF at any speed.

You can leave the hubs locked during the winter months.  In my sammy, when it was a DD, I used to lock up in late november, and unlock in late march, so I could SOTF.

By the sounds of it, finding late model Kick 5.12 stuff to ditch the air diff might be the path of least resistance.

5.13's are hard to find in 99 and later.

I'm pretty sure every automatic '99-up Track/Vit has the 5.125s.