I live in Tucson and have Cox Preferred Internet. I am using a new Motorola SB6141 modem. I say new because I had another modem a month ago and had the same issue with upload speeds and the Cox rep that came to check my lines told me he thought the problem was my modem. I spent over $100 on a new modem and the problem persists.
Here is the problem. When things are going right, I get 64 Mbps download and 6 Mbps or more upload. Sometimes the upload is as high as 20+. After a day or two, my download remains the same, holding at 64 Mbps and the upload dwindles to less than 1 Mbps until it bottoms out at 0 and I lose the Internet totally. Each time this happens I cycle the power to the modem, just as I did with the old modem, and the Internet connects and appears back to normal, i.e., 64 Mbps down and 6 Mbps or more up.
If I call Cox and hold for an eternal about of time, and I get a person on the line, they always say the same thing. They can see my download speeds and upload speeds and agree something is wrong. A technician comes out, cycles the modem, all looks normal and he leaves saying there is nothing wrong on his end. The last tech that came to the house rewired everything from the tap to my modem, i.e., there is no splitters, not nothing between me and the tap.
This problem began occurring about the time Cox doubled the download speeds. Tonight, after experiencing the same issue and after resetting the modem last night, I called Cox and have been on hold now for 38 minutes listening to the same lousy music and some chick telling me "Thanks for holding. We'll be back in just a minute." While holding my internet dropped off completely dropping my phone call to Cox because I have VoIP through Vonage phone service. I cycled the modem, called Cox back and have been holding 45 more minutes.
This is a serious issue. My ADT runs through the Internet, my phone is VoIP, and my Dish Sling works through the Internet. This is really messed up! Wonder why I got rid of Cox television and Cox phone service?