I have a 2000 4 door 4 cyl 5 speed 4wd.
It's my own fault.  I let it get away from me.  The main cross member (welded not the bolt in one I already replaced a few years back) is rotting out. I can put my fingers through it in a number of spots.  Also the rear drivers side shock mount has a hole in it too. 
It just snuck up on me.  I'm trying to figure out my options.  The truck only has 108000 miles on it, runs great, shifter is still tight, clutch seems fine, new tires and brakes within the last year. 
Anybody have any experience with frame repair?  I'm not sure what I am going to do with it right now.
I may just try to soak everything with mineral oil really good to slow it down.
You may want to take a good close peek under your rides.
You might not like what you find under there.

It might sound extreme... but if the truck is sound except for major parts of the frame, put another frame or frame section under it.  I found a complete frame at one of my favorite pick-n-pulls late last summer, already stripped completely down to just the front control arms.  No rust anywhere on it.  I made a note of it on my last visit.  I visited this same pick-n-pull a month ago and the  place had been sold and the 'metal guys' were on site crunching up all the hulks.  Before long it will be damned difficult to find anything at the junk yards because they will all be a thing of the past.  Grab the parts where and while you can find them!

I wonder how hard it would be to weld in a new main cross member......

It's all doable if your truck is worth keeping.

Well, the body with the exception of the rockers is in really good shape.  108000 miles, original clutch, the shifter is still tight, drives great.  I just don't know how much $ it's going to cost to patch up the frame. OR if it's been done

I went on GMPARTS>COM and SUZUKIAUTOPARTS.com  They have the Frame rail $169 before shipping.  It just might be worth looking into replacing.

if i'd be at your place, i'd keep the one you have and buy another one to drive on the road,keeping the old one for parts or a wood buggy,that's my though on it,do as you like , i

 have seen trackers and vitara goes as low as 400$-1000$ and mostly have the same issues: 4x4 dosent work (wire or air leak),tire is fair and has rusty rocker panels or... a broken timing belt. i bought two 2002 vitara's for 900$ both has perfect frame, one the body is a bit bad but still repairable. the one i drive now only had bad rockers and needed front brake pads.

most of the time wen you weld a frame it will rust not far from the patch as the metal is thiner at sum spots due to the rust, you can sure put in a patch but it will rust at another spot.

That was what I was wondering, no matter how good you paint it when your done, how will it hold up?  It's just such a shame, I was driving home today, the gear shift is still tight, no play, clutch is great, runs like a top, great millage , I just don't know, I have a little time before Ihave to really worry about it.  The book value on a trade in is $1700 US.. I need to stay under that, because if a deer ran out in front of me, or if I had a bad accident, and it was totalled, that's all I'd get from the insurance.

just wondering, is it the crosmember that holds the power steering rack and radiator that is rusted out or the one under the oil pan were the a-arm bolt on too? if its the one were the a-arm bolt on too (the one under the engine) id forget about it really,it is a huge job to fix it, you would need to remove the front diff and remove the a-arm and coil springs to replace it, then get the job of putting it strait after. but if its the one holding the radiator and power steering rack that one is not that bad to replace. if you have the time and patience and can make the repair yourself it is a project and would be doable, but if it need to be done by another person i would think it is too much of a repair in labour.

i have checked my 2002 vitara and i got a hole witch looks like the welder from factory missed about a 1-2 inch long on the front crossmember holding the power steering rack, and on the very end rear on the passenger side starts to show a flaky frame, i have sprayed on motorcycle chain lube for now as it all i have for now. not a good time of year to undercoat a truck with the salty roads

Unfortunately its the main one that everything bolts onto.  Either I'm going to try to shoot something on it to stop the rust and seal it, or just keep soaking it with oil.

i find mortocycle chain lube work best on rust spots, its waterproof and made to stick on for a long period of time, i did the bottom doors of my girl friend mazda protege last winter and the grease is still on the bottom doors and tacky. and at 6-7$ a can its fairly cheap too.

trackinstile, are you referring to the solid crossmember the front diff bolts to... or what?  That's a pretty solid piece of steel or... are you referring to one of the tubed cross members in the frame?  IF it is the solid crossmember the front diff bolts to that should be "fixable".  If it is one of the tubed crossmembers, they should be "fixable".  You can pound a tube sleeve through a couple of those.  The rear shock mount should be "fixable" as well.   Even if the patch does eventually rust again, how many more thousands of miles will you have put on your truck and how many years later will it be?  If you got five more years out of it the cost of the repair would be justified.

It's the main cross member that everything bolts onto.  Not the bolt on one.  A buddy of mine just recommended a frame guy that's really good.  Youcan buy the cross member on suzukiparts.com for $150 (I think it's part number 13, you'll see it) also they sell the shock mount too.  I am going to find out how much $ it will cost.  Unfortunately I am not gifted in the welding dept.