I am confused about how the 4x4 mechanism on the newer Trackers works (I am looking at a 2dr 4WD Chevy Tracker ZR2) Is there a tech document or link someone can direct me to for info on how it actually works. 

Is the system as good as the older Sidekicks for off-roading, or lets say a Jeep Wrangler?

Thanks so much.  Jill

It is very simple - when you engage 4WD (4Hi or 4Lo) the transfer lever sends a signal to the electronic controller, which runs the air pump, which causes the clutch mechanism in the front "axle" to engage, so the drive axles are locked to the front driveshaft through the differential.  You don't need freewheel hubs (manual or auto) - the wheels are locked to the axles with drive flanges.

When you move the lever away from 4Hi or 4Lo, the air pressure is released and the clutch disengages.

The rest of the Transfer Case works pretty well the same as the Gen 1 vehicles, except that there is now a synchro mechanism included to make shifting on the fly easier on the gears.

The upside is that you don't have to get out and engage manual hubs, nor suffer unintentional disengagement with auto hubs when backing.  And (for me its the big deal) it's easy to fit a switch to have 2WDLo.  See http://bbs.zuwharrie.com/content?topic=38056.0 

The downside is that the front axle shafts are always rotating, so more wear, and seals can fail earlier.  (Some people say it uses more fuel, but the effect is so small it's impossible to notice.)  Also, there's more to go wrong - the air pump can fail, or the air pipe can pull off.

If you are concerned about the seals, you can remove the drive flanges and fit manual hubs - then you can just engage them for the Winter, or for going off-road.  That gives you pretty much the best of both worlds - just don't expect to save fuel 

Thanks for the reply Ian.  What I was confused about was the following statement I found when searching this forum about the 4wd mechanism on the Gen 2. 

"What happens when you are in 2wd, the front tires rotate the speed of the vehicle* due to the drive flanges and the diff housing is free.. Once you pull the shifter (or push the dash button) to shift the t-case into 4wd hi, the case engages the front ds, the air pump pressurizes the sleeve (if the front tires and vehicle speed match), then you have 2 axle capability. Notice it's not exactly 4wd as the axles are open, and the tires with minimal friction, front axle and rear axle, get the torque/hp. If the front tires and vehicle speed do not match, the sleeve won't engage fully till there is."

The part that concerns me is the "Notice it's not exactly 4wd as the axles are open, and the tires with minimal friction, front axle and rear axle, get the torque/hp".  I understand that 2 wheel drive is really just 1 wheel drive and 4 wheel drive is really just 2 wheel drive (1 wheel/ axle) unless you have lockers.  Is this all this guy is saying or does the linkage between the axles stay open on the Gen2 and you just have 1 wheel drive all the time, but with the choice of any of the 4 wheels.  Man I hope that makes sense!

Cheers,
Jill

The part that concerns me is the "Notice it's not exactly 4wd as the axles are open, and the tires with minimal friction, front axle and rear axle, get the torque/hp".  I understand that 2 wheel drive is really just 1 wheel drive and 4 wheel drive is really just 2 wheel drive (1 wheel/ axle) unless you have lockers.  Is this all this guy is saying or does the linkage between the axles stay open on the Gen2 and you just have 1 wheel drive all the time, but with the choice of any of the 4 wheels.

All he means (or should mean) is that the front and rear diffs are open, so if a wheel loses adhesion, it gets all the torque and rotates in the air, and the other wheel on that axle cannot provide any drive.  If the wheels on the other axle are both gripping, they will be unaffected.  This is exactly the same as Gen1.