I really don't know a whole lot on the subject, but I too have been contemplating the differences between the 242 and 247. I think I would prefer the 242, because I like to be in control, but the 247 is very nice for "set it and forget it" EXCEPT that you have to use MOPAR specific fluid in the 247, which increases the cost of maintenance on the 247. Granted I don't know the price difference between the oils used, but it is something to think about.
A 247 coupled with Vari-lok axles (QuadraDrive), is a very capable system, as long as it's not "Hardcore", but if you want hardcore, you probably need to swap axles anyway.
The 247 uses a mopar specific fluid only from the dealer and is expensive not to mention that stupid progressive coupler. The 242 uses ATF+4 and is cheap (Supertech brand from wal-mart, ALL ATF+4 FLUID IS THE SAME REGARDLESS OF WHAT YOUR DEALER TELLS YOU) so theres points right there. If you want your Jeep to be more like a wrangler then the 242 is the way to go. It offers all the benefits of a full locking 2 speed transfer case and the benefits of a all wheel drive transfer case and you choose if and when its necessary. Add the quadradrive axles and bam, you have the most capable grand cherokee possible (Using factory parts).
Bear - 1999 Jeep Grand Cherokee Laredo - 250,000 Miles, BDS 2" lift, Overland rock rails, Dynomax cat back exhaust, 245/75/16 Kumho KL78's, Rebuilt 4.0 @ 244,000 miles.
Apollo - 2008 Mazdaspeed3 - Mazdaspeed CAI, Mazdaspeed CBE, Prosport boost gauge.
Velvet - 2005 Ford Focus ST - Wife's ride
The 247 is a tough case even behind a V8 in jeep's heaviest and most powerful model at the time. The 247s don't blow up any more than the 242s do so far as I can tell. The progressive coupler is a serviceable item, and it will wear. The 242 has no similar part, but that doesn't mean it's fair to say that the 247 is less reliable for that. That's like saying an open diff is better than a trac lok because the trak lok will need to be rebuilt eventually
Further to that, most of the PC failures are due to neglect or poor maintenance.
As TJ pointed out, most reported 247 failures aren't the 247 at all, or at worst are the PC. I have yet to see one "blow up". I'm sure it's happened, but I've not seen it. I'm not shy about crapping on the WJ's for being junk either, but the 247 is nothing to complain about.
So back to my question earlier. Am I doing any harm by waiting to fix my PC??? I can use 4lo if I need 4x4 in a pinch.
Change your fluid, purge the air out of it and see what happens.
Will do. My jeep is in the shop now having a new jasper motor put in. When I get my jeep back I plan on changing the TC Fluid. hasn't been changed since I bought it in march. That being said its been setting in my driveway for close to 2 months.
Thanks for all the help everyone . If the fluid change doesn't help I will fix the PC in the fall.