The blend door of the Cherokee is like most things with the Cherokee you either have it or will have it. Hopefully my findings here will help you out.
1. Remove the blend door motor module by pulling back the carpet along the transmission tunnel wall on the passenger side and removing the (3) 8mm screws with a ¼ socket set with a universal joint makes things easier.
2. Remove the Philips screws on the plastic carefully as you want to maintain the alignment of the blend door shaft and the internal potentiometer (BLUE POT). Take a photo or make a drawing of these positions before going further.
3. Now pull all the gears out and using a clean rag and toothbrush remove all the old dried up white lithium grease from the gears and motor shaft. Also do not to forget to clean the grease out of the module case, use the rag and cotton swabs to get into the gear shaft holes.
4. Apply a thin coating of NEW FRESH white lithium grease to the gears, motor shaft and onto the case module where these points contact and reinstall everything back into the module case and reseal it back up replacing the philips screws. (Remember to keep that blue pot and blend door shaft alignment).
4A. NOTE this should be the first step after removing or reinstalling the blend door module back into the vehicle. But, test the blend door by using your fingers and make sure the door moves freely and that the shaft is not broken and that the door itself is not just outright jammed/jamming up when you move it. There is some fair amount of torque needed to move that blend door back and forth hence all those gears in the module but it should be movable by using your fingers, if this door is not moving properly this repair will most likely not fix the issue you are having.
5. Reinstall the blend door module back into the vehicle and you should be DONE!
NOW FOR THE FUN SH!7 STUFF
3A. (Violet Arrow) If the small gear going to the motor seems tight then you are most likely correct. This gear has a tendency to swell up and becomes so tight on the shaft that most of the power from the little motor is wasted just trying to turn this gear alone. (How to test for this issue; Gently pry the motor out and install just this gear into the plastic case with new grease applied, if you have tension while trying to finger turn this gear you need to carefully use a rounded needle file to open the gear hole up. (DO THIS SLOWLY AND INCREMENTALLY CLEANING THE GEAR HOLE OUT WITH A COTTON SWAB TO REMOVE ANY PLASTIC, RE-APLLYING GREASE AND TESTING UNTIL YOU HAVE REMOVED THE TIGHTNESS ON THIS GEAR. DON’T RUSH THIS JOB AS YOU DO NOT WANT ANY SHAFT WOBBLE ON THIS PRIMARY DRIVE GEAR, YOU JUST NEED TO REMOVE THE TENSION FROM THE SHAFT THAT IS ROBBING THE TORQUE FROM GETTING TO THE BLEND DOOR).
3B. YES, this first gear is a different color because it is a different plastic then all the other gears. It’s a harder plastic as it should be for meshing with the worm gear on the motor.
3C. YES, my metal notches are chewed up a bit from me using a quarter to manually get the motor to rotate back over from HEAT. But, yes a quarter fits these metal notches perfectly.