1999 jeep grand cherikee 4 wheel drive not working

SOURCE: 4x4 wont work in a 97 jeep

The only Solution to this is 1 of 2 Things ! The Shifter Linkage is Off of the Transfer Case 2 The Transfer Case is Shelled out and needs to be Rebuilt. Check underneath on the Transfer case for any Noises when in 4X4 and Check the Linkages. Please Rate my Response, I need all the Help That I can Get! Thanks!

SOURCE: Service 4 wheel drive

The service 4 wheel drive light comes on because there's a problem. The biggest causes of this I've seen are a software glitch in the final drive control module which the dealer can fix by reprogramming and the other is usually the electric actuator on the front axle housing. The only light that comes on by a timer is the one that says, "perform service" in your overhead console or odometer.

SOURCE: 1999 jeep grand cherokee all time four wheel drive will not engage

Sounds like the splines on your transfer case gear are ground down

SOURCE: Jeep grand Cherokee stuck in 4 wheel drive.

Hello nicky...Check the transfer case linkage and see if it is working freely....the linkage could be hung between 2wd and 4wd. You may be able to keep working the linkage and free it up...the bushings may be worn and the linkage may need adjustment also. The transmission mounts will wear and keep it from moving freely. Try driving in reverse for a block or so...a lot of the wrangler and cherokee owners claim this works for them.
Good luck...i hope this helps, please rate me a fixya.

SOURCE: How to shift a 1998 jeep grand cherokee into 4 wheel drive

Four low is almost never used. I use it on very steep rocky or muddy trails in the woods or to pull someone out of mud or a ditch. Though some will shift standing still it is best do do this while rolling. Four high can be shifted at low speeds of 2 to about 35mph (higher also but not really good idea) Low can only be shifted between 2 to 10mph. If you find yourself stuck and unable to shift because you aren't rolling you can also turn the engine off, engage the transfer case and re-start. That avoids having the gears clashing together. Best rule is if it begins to grind, don't force it.