Since this happening on wifi i would suggest you to try changing wifi channels will avoid interference and that will give better speed and connection.  

If other Wi-Fi sources such as neighboring wireless access points are using the same wireless channel, this may cause intermittent connectivity issues, even if the competing signal is relatively weak. Changing the wireless channel within the  gateway can improve connectivity.

http://arris.force.com/consumers/articles/General_FAQs/G34-G36-Changing-the-Wi-Fi-Channel

After changing wifi channel as recommended on the link restart the modem then we would request you to monitor the connection for next 24hrs.

I had the same issue, but then I hooked up an older wifi router to my G34.  That solved the problem for me.  I don’t think this helps with a good solution for the G34, but it was a workaround that worked for me.

If you have the same problem after changing the Wi-Fi channels, I suggest to reprovisioning the modem with internet service provider.

If you tried all the possible troubleshooting steps, then I would suggest visiting www.arris.com/consumersupport for further assistance.