Chances are that you'll find this household repair to be pleasantly manageable, even if it's your first.
In fact, the biggest challenge might be managing the greasy situation waiting in the gearbox, so make sure that you have some shop towels handy.
Other than that, disassembly and reassembly of the mixer is easily handled with a couple of screwdrivers, a pin punch, pliers, and a hammer.
There are a few tricks that make parts of the repair easier, so make sure to read each step.
1. Remove the drip ring.
The planetary drip ring decorates the mixer and contributes to the seal around the planetary. It has to come off in order to pry the planetary off of the mixer.
Carefully place a flat head screwdriver against the upper lip of the planetary drip ring, then lightly strike the screwdriver with a hammer.
The drip ring is only held on with a little bit of tension, so a light tap should make it fall right off the mixer.
2. Remove the planetary shaft roll pin.
A roll pin holds the planetary to a shaft coming from the gearbox. Trying to pry the planetary from the mixer won't do any good with the roll pin still in place, so it must be removed.
Using an appropriately-sized pin punch and a hammer, lightly tap the the roll pin out of place.
3. Pry the planetary from the mixer.
With the roll pin and drip ring removed, the planetary is ready to be freed from the mixer, however, it is still held snugly in position by the tight fit of its internal gears.
The best way to remove the planetary is by using a couple of flat head screwdrivers as pry bars.
Position the two screwdrivers in the indentations on the sides of the planetary and carefully pry the planetary off.
4. Remove the five motor housing screws in the front.
Now that the planetary is off the machine, the next order of business is to remove the motor from the mixer.
The motor is located in the top half of the two major sections of the mixer. To lift the motor off the mixer, all fasteners connecting the bottom and top halves of the mixer must first be removed.
The first set of motor housing screws to remove are located in the ring underneath the planetary. Remove the five front motor housing screws with a flat head screwdriver.
5. Remove the four motor housing screws in the back.
There are four more motor housing screws in the back of the mixer that must be removed with a flat head screwdriver.
Attention! One of the rear two motor housing screws will have a lock washer on it. This lock washer screw is a fail-safe in case the other screws shake loose. Take note of the screw when you disassemble, because it must be returned to a rear position in the mixer.
6. Remove the rear housing cover.
The rear housing cover of the mixer helps to hold the two halves of the mixer together.
Only one Phillips head screw holds the rear housing cover to the mixer.
7. Pull the power cord strain relief out.
The power cord strain relief simply pulls out of the rear of the mixer.
8. Lift the motor housing off of the mixer.
With the housing screws removed, the rear cover off, and the strain relief disengaged, the motor is now free from the lower half of the mixer.
The front end of the motor housing is actually part of the mixer's gearbox that attaches onto a gear shaft, so it will still be partially secured onto the mixer.
Lift the motor housing straight up to pull it off the gear shaft and away from the mixer.
Set the motor housing aside. You'll need to transfer grease to the gearbox portion of the motor housing in the next step.
9. Remove all excess grease from the mixer gears.
You will discover a large amount of grease on the mixer gears--this is normal.
However, excess grease on the gears must be temporarily removed in order to access the gear tower assembly and remove the worm gear.
Use a putty knife to scoop the grease off of the gears. Place the grease in the upper portion of the gearbox located on the top half of the mixer.
The grease must be returned to the gears after the worm gear replacement is complete and before returning the motor housing to the mixer stand.
After removing enough grease, the worm gear will be visible in the gear tower assembly. Inspect the gear for wear and damage to verify that it is the cause of the mixer malfunction.
10. Disengage the gear tower assembly.
The easiest way to access the worm gear is to remove the entire assembly
The gear tower assembly is only held into place with two or three Phillips head screws. Unscrew the tower assembly screws and lift it from the mixer.
11. Remove the gear tower roll pin.
A roll pin holds the gear tower gears to each other.
Again using a hammer and a pin punch, gently strike the gear tower roll pin until it comes out of the tower assembly. You may need pull it with a pair of needle nose pliers the last little bit.
12. Pull the tower gear out of the assembly.
The tower gear pulls right out of the bottom end of the assembly after the roll pin is removed.
13. Remove the old worm gear.
The old worm gear is finally ready to come out of the tower assembly, and it will simply pull out.
There is a washer spacer on each side of the old worm gear that must be transferred to the new worm gear.
Make sure to save the two washers and set them aside for reassembly.
14. Install the new worm gear.
Place the two washer spacers you saved on the new worm gear, one on each side.
With the washers on, install the new worm gear into position in the gear tower assembly.
This completes the installation of the new worm gear into the KitchenAid mixer. Finishing the repair is just a matter of reassembly.