The mixer makes noise at stir speed. If I press down on the black contact plate at the rear of the mixer, the grinding goes away. I am not sure if it is the rear motor bearing or something else.

Good Morning,

There is a spring inside your mixer attached to the speed control switch and speed control arm, the spring can sometimes get caught on the slide bar that is just below it inside the mixer. The other reason is that the speed control switch plate in the rear of the machine (that the spring attaches to) vibrates the three speed adjustment screws out or in and the spring will pull the speed switch (control arm that you use to control mixing speed when using the mixer) back to the stir position after you try to turn the mixer off.

If it is a spring problem you will have to do a full tear down to get at the spring and either free it or replace it. If it is a problem with the adjustment screws on the speed plate, that can be handled at the rear of the machine and is twice as easy to get at but sometimes much more frustrating to adjust. There are "YouTube" videos on the internet that will walk you through the process of adjusting your speed control plate just Google "adjusting speed on kitchenaid mixer" I hope this helps. please let us know if it does and if you have other questions just post them here and we will "FixYa"

Something is out of balance, the front or rear bearing sounds like the culprit. the rear bearing is a relatively easy fix from the rear of the machine the front bearing is a little harder and will require a full tear down,


There is a sometimes problem that can fix a bearing problem that is actually not a bearing problem but a loose nut problem. At the rear of the mixer after you have removed the rear end cover get down to eye level with the rear of the mixer look to the right and left of the copper and black plastic speed switch plate and you will see a 3/8 nut on each side of the rearing housing, these sometimes get over tightened or come loose, you need a nut driver to operate them. tighten them up and turn on the mixer if there is a noticeable change in the pitch or sound of the mixer or the knocking gets worse turn them back the other way and listen again, if the knocking goes away then it was the nuts, it is only a sometimes fix, but it can be the problem,
if it is not the bearings i would generally start my fix by going to the gears first, The worm gear can be going and that will also take a tear down to fix but easy to do, you will need a new gasket, grease, a new worm gear and plenty of paper towels, it's messy. how long has it been thumping? how old is the machine? the worm gear fix has several really good you tube vids for this, just type in broken kitchenaid and you will get several, please let us know if this helps

Did it start clattering before or after it was re-greased? The K5ss by Hobart is an excellent mixer and there is no reason why it can't go on for a bunch more years. First you can get clattering if the brushes are less than 5/16th inch long, But that is not usual.

I would think that the rear bearing which is in the center at the rear may be more your problem, That bearing is behind the speed control switch and behind the governor (don't discount the governor being the problem) and is attached by two 3/8th nuts and slides onto the two guide slides that hold the motor parts in place. What i have found over the years is that 1.) the studs can bend (happens but not often) 2.) the bearing which is in the center of the big aluminum housing, (Called rear bearing assembly) moves over the years and causes humming and clattering.
So what to do about it? Loosen the two nuts a turn or two (do not remove) look at the top of the the bearing assembly and you will see a metal tab (used to attach the rear cover) (make sure the bowl and beaters are not attached to the machine) now plug it in and turn it to stir speed or number 2 position, put your finger on top of the tab and press down while the mixer is running, you should hear a change in pitch, and it should effect the clattering noise, (It will go up or down, or you may hear a new noise a light humming) (The humming is caused by the armature no longer in the center of the motor field and getting to close to the stator of the motor while it is operating, when it is out of center the developed magnetic field that causes the armature to turn gives off the humming noise because it is out of center or balance) if you notice that the clattering gets louder or softer by pushing down or pulling up you have to play with it to find the sweet spot, when you find it tighten the two nuts down just enough to hold it in place and no more. It takes a while and you wont hurt the machine but never go above speed two while doing this. If that fixes the problem you may have to do it more than once as the machine continues to age or if you move the machine around a lot. the real problem is the armature needs replacing (if this is the problem). Next you may have the machine timed wrong and that has to do with the speed control switch entirely, let us know what you find if these are not the problems we have a ways to go but they are the usual culprits with your symtom.

it was stuck on high speed because the phase control board went out, your fix may not be absolutely 100% and it is now causing an uneven distribution of the electric charge in the mixer and it is arching. My recommendation is to replace the speed control board (black and copper plate) and the phase control board. i bet it fixes the problem as these are the two parts that regulate the electricity in the mixer. Hope that helps. Buy the way if you don't fix the problem and continue to use the mixer you may have to replace the motor eventually as you can cause the armature and stator to short or burn out.

Get a Copy of the Repair Part List from Kitchenaid.com.
First thing I would do is to check the two Motor Brushes (one on each
side of the Motor Housing). Make sure they are not worn out, and when
inserted, they must both make contact with the Motor Coils. If even
one of them is not in contact with the coils, the motor will not run.
You can also remove the Motor Housing and visually verify that they
are touching the Coils.
You may also need to adjust the mixer speeds:

Remove the screw holding the End Cover and locate the three screws from the Control Plate.
All three (2 top left and right, and 1 bottom) must be adjusted. Make sure that the Control
Plate is not damaged in any way, contacts are not charred or burnt,etc...

1. Loosen the lock nuts enough & Turn the 2 top screws clockwise until they cannot be turned
anymore. Leave the bottom screw alone for now.
2. Use a dab of white paint or paper whiteout to mark the positions of the Phillips screws.
3. Plug in your mixer and Set the speed selector to "Stir".
4. Turn each top screw One full turn couterclockwise (alternating between Left and Right)
Keep making one full turn at the time (for both left and right) until the motor starts running.
5. Put your hand near the Agitator shaft and allow it to brush your finger slightly. Use your
watch or clock and start counting the number of times the shaft touches your finger in
60 seconds. The correct count should be 60 RPM (Rounds Per Minute). If it is less
or more than 60, give each screw 1/4 turn counterclockwise or clockwise and start counting
again. Now tighten both lock nuts.
6. Set the speed selector to "6" and turn the bottom screw either clockwise or counterclockwise
to achieve a speed of 180 RPM.

For your reference, the planetary RPM's for the 5-qt. tilt-head Artisan Stand Mixer are as follows:
Stir speed - 60
Speed 2 - 95
Speed 4 - 135
Speed 6 - 180
Speed 8 - 225
Speed 10 - 280

Get a Copy of the Repair Part List from Kitchenaid.com.
You need to adjust the mixer speeds:

Remove the screw holding the End Cover and locate the three screws from the Control Plate.
All three (2 top left and right, and 1 bottom) must be adjusted. Make sure that the Control
Plate is not damaged in any way, contacts are not charred or burnt,etc...

1. Loosen the lock nuts enough & Turn the 2 top screws clockwise until they cannot be turned
anymore. Leave the bottom screw alone for now.
2. Use a dab of white paint or paper whiteout to mark the positions of the Phillips screws.
3. Plug in your mixer and Set the speed selector to "Stir".
4. Turn each top screw One full turn couterclockwise (alternating between Left and Right)
Keep making one full turn at the time (for both left and right) until the motor starts running.
5. Put your hand near the Agitator shaft and allow it to brush your finger slightly. Use your
watch or clock and start counting the number of times the shaft touches your finger in
60 seconds. The correct count should be 60 RPM (Rounds Per Minute). If it is less
or more than 60, give each screw 1/4 turn counterclockwise or clockwise and start counting
again. Now tighten both lock nuts.
6. Set the speed selector to "6" and turn the bottom screw either clockwise or counterclockwise
to achieve a speed of 180 RPM.

For your reference, the planetary RPM's for the 5-qt. tilt-head Artisan Stand Mixer are as follows:
Stir speed - 60
Speed 2 - 95
Speed 4 - 135
Speed 6 - 180
Speed 8 - 225
Speed 10 - 280

I am not sure what has happened to your mixer but, select
different speeds from Stir to 10. If it runs OK, then there is
nothing to worry about, otherwise do the following to re-adjust the mixer's speeds:

Get a copy of the Repair Part List of your model from Kitchenaid.com
Remove the screw holding the End Cover and locate the three screws from the Control Plate.
All three (2 top left and right, and 1 bottom) must be adjusted.

1. Loosen the lock nuts enough & Turn the 2 top screws clockwise until they cannot be turned
anymore. Leave the bottom screw alone for now.
2. Use a dab of white paint or paper whiteout to mark the positions of the Phillips screws.
3. Plug in your mixer and Set the speed selector to "Stir".
4. Turn each top screw One full turn couterclockwise (alternating between Left and Right)
Keep making one full turn at the time (for both left and right) until the motor starts running.
5. Put your hand near the Agitator shaft and allow it to brush your finger slightly. Use your
watch or clock and start counting the number of times the shaft touches your finger in
60 seconds. The correct count should be 60 RPM (Rounds Per Minute). If it is less
or more than 60, give each screw 1/4 turn counterclockwise or clockwise and start counting
again. Now tighten both lock nuts.
6. Set the speed selector to "6" and turn the bottom screw either clockwise or counterclockwise
to achieve a speed of 180 RPM.
For your reference, the planetary RPM's for the 5-qt. tilt-head Artisan Stand Mixer are as follows:

Stir speed - 60
Speed 2 - 95
Speed 4 - 135
Speed 6 - 180
Speed 8 - 225
Speed 10 - 280

I had the same problem. Part #25, the "control plate assembly" It has a set of points on the lower, inside. These points turn the motor on. You can watch it as you go from off to stir. If at that setting the motor doesn't start, be very careful and bend the lower point contact up just a bit. The 2 points should make contact earlier, and turn the motor on.

I determined that the switch that controls whether the mixer is on or off is controlled by a copper bar with a contact. The contact got fused to the copper bar, possibly due to a short. Since the contact got fused to the copper bar, the circuit was always connected, so the mixer was always on. The solution was to 1) unplug the mixer, and 2) take a screw driver and gently pry the contact away from the copper bar. When the mixer is in the off position, the copper bar and contact are no longer in contact. When the mixer is on, the copper bar and contact make contact. My mixer now works just fine. Yea!

The repair manual says that the mixer can make this grinding sound at slow speed, like stir or 2. This is normal, especially until it warms up. This is the sound of the gears turning at slow speed.