hey guys how would i go about checking my rear axle bearings on a dually? when i go down rough roads or hit a decent bump i'm hearing a strange rattle from the back of the truck. but i don't hear it when i have a trailer on. then yesterday after the truck sat for a hour i heard a crunching noise from the back end that went away as soon as i was rolling. my truck has 350k on it and i don't know if they have ever been changed before. i haul campers cross country for a living so don't want to end up broke down on the side of the road
btw it's an 08 quad cab cummins dually

thanks
jason

 

Have a look at your shocks too. They can make some interesting noises as they rust away.

Aside from that, jack up the rear of the truck, and spin the tires by hand. See if they feel crunch, or notchy. If they do, time to go digging in there.

 

ok thanks i actually have new shocks,air bags,compressor and tank sitting here waiting to go on was just trying to figure out the noise before i put it all on.i even thought it might be my hub caps so i pulled them but it didn't make a difference .
jason