Images of welch plug on jeep grand cherokee overland 2.7 CRD

SOURCE: jeep cherokee 2001 box shape

Check your coolant to see how low a temp it's good for. What u are describing is the failure of a freeze out plug. They are there to protect your block and head from cracking in cold weather, if you don't have sufficient anit-freeze protection (old anti-freeze, or not enough anti-freeze). If the water in the engine freezes, the freeze out plugs are designed to be a weak point, popping out to relieve the pressure of the freezing water, hopefully saving the head and block from cracking. The other reason for failure is corrosion due to, again, insufficient or old anti-freeze. To remove, u just need an old screwdriver and hammer, knock a hole in the plug w/ the screwdriver, pry it out. Clean up opening, install new one w/ block of wood and hammer. Of course, the location of the freeze out plug is what determines how much room u have to do this, so u have to decide if it's easier to pull the engine, or remove the head. It would be wise to pull the engine, and change all the plugs as angelo63 suggest, when done flush the system, adding a 50/50 mix of anti-freeze/water.

SOURCE: i need to drain my radiator on a 2002 jeep grand cherokee

On many of these, the drain is on the right front of the radiator, sometimes requiring removal of a small panel in the grille or the entire grille. The ones I've serviced, after geting to the drain I've found that it dosen't turn. It is far easier to ignore the drain altogether and remove the lower hose at the radiator. Don't do this on a hot engine unless you like hot antifreeze baths! (I don't)
Good luck

SOURCE: 2004 Jeep Grandcherokee - Transmission Maintenance

I'm going to guess since you didn't mention which fluid...Transmission?
First find out which unit you have (usually an id tag on it somewhere ) Then look up what kind and how much fluid in your owners manual (usually around four quarts...unit holds more but you can't remove it from the pan) Remove all pan bolts and lower pan. (some units have a drain plug, use it first if you have one ) you will see the filter attached to the valve body. remove it and install the new one, Make sure all gasket material is removed from pan and trans. Clean any metal etc from pan and internal magnet (there is always some in there but should not be a ton of it) Then put pan and gasket back. Make sure you can turn each fastener easily to make sure they are not cross threaded and only tighten them after they are all in there. Bolts do not have to be tightened down like they never should be removed again (snug then a little bit more)tighten in an X pattern not a circle.Replace about half of the fluid with car off, then put in remainder while running. Put your foot on the brake and shift to reverse then drive a few times then check fluid level.Low is bad, a tiny bit (less than half inch) over is OK.
Drive for a short ride, check again for leaks and re-tighten if any are found.
If trans was exceptionally dirty and yours has a drain plug, I recommend that you use a generic oil on the first change, then in a week, drain oil again and re-fill with good brand name stuff. and perhaps a bottle of lucas conditioner.
Good luck!

SOURCE: 2004 jeep grand cherokee overland, 2.7 CRD, half

Sounds like it is in 4 wheel drive mode.
If you have a switch to disconnect the 4 wheel drive it may not be working.
If the vehicle is full time 4 wheel drive or computer controlled 4 wheel drive you have most likely a locked in full 4 wheel drive mode situation.
Not good on dry pavement.