2004 grand cherokee is slipping in multiple gears

SOURCE: 1994 JEEP GRAND CHEROKEE-TRANSMISSION "SLIPS" ON TAKE OFF.

First of all make sure you are checking the fluid right. Some people do not know that in order to check transmission fluid the engine needs to be running and the temperature needs to be sort of warm althought you should be able to get a good Idea just by the engine running. In this instance you might have a governer valve that isn't properly working to shift the engine when hydraulic pressure reaches a certain PSI. I would suggest having it flushed and put in new fluid and filter. If this doesn't work the problem is more serious and might need some professional assistance.

SOURCE: 1997 Jeep Grand Cherokee transmission or transfer case

As I said, trans fluid keeps the internal components "alive"... Low fluid level can cause burning of internal clutches, premature hardening of seals (essential to proper transmission of fluid pressure) as well as lubrication of necessary gear components such as planetary gear set (which can cause whine etc. which you now have) All of these components rely upon a constant flow of fluid for both cooling and lubrication. Depending upon how low and how long these parts had interrupted fluid flow, directly influences how much damage was done. I take no joy in telling you that you may have damaged your unit, I'd be far happier if I could give you a quick, inexpensive fix. But based upon what you have said, If I was working hands-on with this problem, I would make the recommendation I've already made. There are pressure tests etc that can be done at a transmission shop to verify to some degree of certainty what is going on within your unit. Hopefully they may find something other than what I've said. At this point though, it is wise to have it checked out by a professional, before you become stranded at a time when you can least afford to be.

SOURCE: 1994 jeep cherokee linkage

Problem sounds like an internal pressure problem not a cable. If you are able to shift into all gears using the shifter, the linkage is being moved properly. It cannot "come out of gear" by way of the shifter.
In reality, if you were able to manually put the shift lever on the transmission into any particular gear without any shift cable at all attached, it would stay in that selected position forever till you got under there and moved it again. Depending upon what transmission you are using you may have a throttle cable running between the trans and throttle lever on the throttle body...this may have something to do with your problem but would also affect shift points. Any electronic shift controls are also suspect at this point. have it checked by a competent shop. In not being there myself, I can only offer my thoughts on what I would test going into the problem...after testing a better evaluation can be made. Good luck...Hope it's something simple.

SOURCE: Transmission slipping or stalling around 45 mph and down shifts

if fluid isn't burned, shifts aren't slipping or flairing and you did not find a large amount of debris in the pan, chances are that the electronic shift control is malfunctioning. Have someone check it out.

SOURCE: My 1995 Jeep Grand Cherokee transmission slips in overdrive

sounds like a possible shift solenoid. If it's due for a fluid change, do that and add a container of lucas trans conditioner. Likely you have a drain plug on the pan so if the fluid was recently serviced, just drain a quart out and replace with the additive, then top off.
If the condition does not change within a week, likely you will need better diagnosis from a reputable trans shop.