Definitely check lug bolts. Lost two days of planting time trying to find a squeak in the rear of a tractor.
Sounded more like an axle bearing. Pulled the dual, didn't notice any shiny spots. Pulled the inner tire, pulled the taper lock hub. Found a 10 foot 4 inch piece of pipe to slide over the axle for leverage, could not make the axle wiggle, seal was still good, ergo not a bearing. Wire wheeled everything till shiny and reassembled. Hooked back up to mounted bean planter, squeak was back. Pulled just the dual and aired the inside tire up, no squeak. Reinstalled the dual, then used the one inch impact to run the dual bolts down, no squeak for a day then it was back.
Rim and hub was a aftermarket unit, just loose enough where the rim fits over the hub for the tiniest amount of movement, not even enough to shine anything up but enough to make noise. Uses regular grade 8 fine threaded one inch bolts with big flat washers instead of a standard lug bolt with a taper. Pulled the dual back off, applied quick metal to the hub boss where the rim is supposed to ride, then bought special cupped washers that would dig a little into the rim, ran em all back on with the one inch impact, no squeak as of yet.