Steve777: You are wonderfully brave to take apart a mixer gearbox! I am in awe. The only question I have concerns the material of the gearbox case. Is it a steel case, or is it plastic? If it is a plastic case, then the problem could be caused by heating up due to the load, followed by distortion due to softening of the warm case. Several reviewers on another site encountered plastic gearbox cases in the newer mixers. But with a bit of luck, you might have one of the golden-oldies with a steel case. best regards, Peter-A

I think there are a few mistaken ideas above. 1) The idea that you're going to use a mechanical device more or less often, or stress it with a greater or lesser load doesn't exactly tell you whether you need a certain size machine. If you buy a mixer with modest power output and overload it, you begin to damage it regardless of whether this is once a week, once a month, or ten times a day. This is because overloading an electric motor creates more heat in the motor windings than the design is built to handle. The heat begins to melt the insulation in the motor windings (a mass of copper wire wound in a 'pile' and separated only by a coating of varnish on each strand of wire). Melting this insulation completely between any adjacent wires creates a short circuit in the windings. Unlike a short circuit in your house wiring, this usually won't make the unit fail all at once, but it will reduce the power, however slightly, causing it to overheat more on the next use, causing yet more overheating, and on and on. So the real question is, how much of an overload can a particular machine take before this happens, and no one is going to give out that info. Some commercial machines of all kinds are rated for a certain constant load, with the extra advice that they can take a certain occasional or transient overload. They may say something like "approved for occasional use at 112% rated power not exceeding xxx minutes". Smoke from the mixer is a definite sign of the insulation melting as mentioned above. You get to decide (gamble) how much of this you're going to do. 2) readinglady says: "Ignore the wattage. Most companies list the watts a mixer pulls from the outlet. Wattage is not a reliable indicator of power" This is incorrect. No, don't ignore the wattage because power is what wattage tells you; it is is precisely a measure of power. 3) The Hobart (commercial) mixers differ from others in that they use a geared transmission. This is a set of gears just like the ones in your car. For a heavy load, like going uphill in your car, you shift to the low gear to avoid over-stressing or overheating the motor. Lower gear settings give lower mixing speeds. The consumer mixers don't have gears. Rather, they produce different speeds via an electrical switch similar to a lighting dimmer. The different speeds here aren't to allow for load size, but for different mixing options - slow for cake batter, high for egg whites, etc. This arrangement does nothing to protect you against overheating the motor. If your motor is overheating, that's a sign saying you have too much stuff in the bowl. A mixer with a 5 qt bowl or 6 qt bowl doesn't mean you can load it with 5 or 6 quarts of anything. A mixer could have a ten gallon bowl, but if it has a toy motor it might only mix a handful of bread dough. The difficult thing here is, sad to say, that you can get some hints at a forum such as this one, but in the end you will buy something based on a best guess. If you plan to make large batches of heavy dough, regardless of how often, you may be well advised to go for the highest power machine you can get. Also, mentioning the Hobart mixers is academic for most of us. Hobart is now commecial only and mighty expensive; Hobart no longer makes the Kitchen Aid machines. A Hobart mixer would be great, but you're talking about $2,000 plus.

My advice is to return the KA and buy the Cuisinart 5.5-qt, 800 watts at Overstock (last link below). The sale is on the white color. KA no longer has the reputation it used to have. Its quality has gone sour since the DeLonghi made a strong stand mixer for Cuisinart. After alot of research & readings, I changed my mind on a KA purchase and got me a Cuisinart 7-qt. Originally, I had my eyes on the Viking but price was still bigger than my pocket. I was happy to find the Cuisinart has a 3/5-yr. warranty; whereas, KA has only 1 year. I had my Cuisinart for 2 yrs. now and just love using it for just about everything. Mine is the brushed chrome and it looks sleek on my granite coutertop too ;o) If you'd like to read more reviews from customers who purchased it, go to Amazaon and find out. America's Test Kitchen also agreed that the Cuisinart is a better purchase than any KA model. For reviews on Amazon: http://www.amazon.com/Cuisinart-SM-55BC-2-Quart-12-Speed-Brushed/dp/B000MTIUSS Here is a link that might be useful: Cuisinart 5.5-qt. White @ Overstock.com

I also had a more than 30 year old KA (Hobart) mixer. Mine was white in the bowl lift model - I don't think they even had colors when we got it. It was still going strong but I wanted to upgrade the capacity and get something that went better with my new kitchen so we replaced it with a dark pewter Pro 600 KA. The old KA was passed on to one of my sons. I had read that KA had problems with plastic in the gear box for a while but they have resolved that. I hope so - we have had the new mixer for almost a year and it has been doing fine so far - including big bread batches. The slow start is a nice improvement - flour doesn't fly everywhere when I start it up like it did with the old model. I also like having burnished (i.e. metal surface) beater and dough hook instead of plastic covered - the plastic covered beater had to be replaced a couple of times over the years when the plastic started to flake off. I wish they would do stainless steel beaters that could go in the dishwasher - the one bad thing about the burnished ones is having to hand wash. If you put them in the dishwasher, the detergent reacts with the surface and they get rough.