Hobart Mixer D300, When mixing mashed potatoes paddle will only turn in low gear. When product is mashed with milk added it sometimes will turn in 2nd gear, but never in top. When this happens, motor is turning with no appreciable loss in speed or increase in amperage. Could this be a clutch adjustment/replacement problem or a worn gear (gears appear O.K.)?

The Hobart H600 is a 2 horse power, 60 quart mixer, it can be used for many things in the kitchen. It can be used to make about any kind of food that needs mixed, wiped or kneaded. It works well in a pizzeria for all facets of making pizza from the dough, to shredding the cheese with an attachment, to a restaurant that makes mashed potatoes and fresh bread, to a full service bakery.
However, the biggest thing that you need to know is the capacity of the machine. As overloading the machine can cause damage that may be costly and take a technician to fix. I do not know what attachments you currently have so I will go over a few of them.

The main attachments are a Wire whip, Flat beater, and Dough hook. There are three different types a "D" wire whip (has many wires and is evenly spaced) this is used to whip egg whites, whipping whip cream, etc. The "C Wing" (has six tines in it) is used for items that are heavy for the D wire whip, like whipping potatoes or icing. The last is the "I" whip is similar to the D wire whip just with less tines. The flat beater is used to mashing or mixing examples are mashed potatoes before they are whipped, cake mixes that do not require whipping, batters and icing. The Dough hook is used for kneading dough examples are pizza dough, bread dough, etc.

The biggest thing when using your mixer is to know its capacity for the material that you are mixing. All though this is one of the bigger machines it still has limits. You should refer to this the following link for the capacity of your machine: https://my.hobartcorp.com/resourcecenter/ProductDocumentation/F-7701.pdf

There are also a few attachments that can be put on to the No. 12 attachment hub. A few of these are a vegetable slicer-grater and meat grinder.

A thermal overload is an option on the D300 and is self resetting. Assuming your machine is being operated at it's full rated voltage, you might have to cut down on the amount of dough you are mixing. If I recall correctly, the relay and overload is located in the base or behind the speed selector plate.

I have a D300 mixer and the 2nd gear kind of misses or just vibrates a little what is this?

Keys are removed using a small punch and a hammer. The punch of choice is called a ***** punch

You have a gear with broken teeth or one sliding out of place because the brass shims are eaten up. Hobarts have what is called a planetary, round head where the grease caps are, and there are no clutches for this planetary. These units are not made to change gears while unit is running (#1 problem of gear failure) (#2 is overloading the bowl) Hobarts need a really stiff GREASE, not oil. If you decide to take the planetary apart, get all the syrup out and replace with a stiff axel grease. It is a very difficult job replacing a gear & ALL the shims. The round head where the grease caps are can easily be removed to do this.

more than likely you have an electrical problem,loose wire, bare wire.
check your cord then open up the back see if you have a bare wire or see if you can spot a black spot were it may have arked

All that I could find for you is the manual

seems their website is not up and running at the momment sorry I Could be of any more assitance to you nice mixer by the way.

in what speed?any noise?what were you mixing?it may be a sheared key or broken gear.let me know.

Sorry so late for the reply.When the product slows down---how slow?can you grab the shaft and stop it from moving?What product are you mixing?