rear diff queations

So this is ben going on for awhile now and i wana take a roadtrip just kinda worried...now and then driveing my truck it feels like a vibration in the rear of my truck....new u joints and carrier bearing checked all u bolts and drive shaft bolts and leaf spring bolts....had the caddy wheels ballanced.....but now and then it rides rough and sometimes smooth....one of my tires seemed like it had a flat spot cause it looked to be bouncing on the ballancer but ballanced fine...could this be maybe a axle or pinion bearing bad?....I keep the gear oil changed every 30k and never has any off metal floating arond so that's a good sign but still alittle worried.....and ideas?

I would try this check.Jack it up so the rear end is off the ground and remove both tires.I would remove the brake drums.Now simply place a aerosol can as close as you can to the hub and rotate it(have it about a 1/8 to 1/4)and check for any variation.Basically your checking for a bent hub and also check your bearings for any noise and or funny feel.I know the bearings won't last forever but,these can create a vibration.Idk about about the pinion bearing specifically,but these tend to leak around the driveline hook up if going out.If the ring/pinion are sloppy or feel a clunk then this would be really obvious.I had a bent hub shaft idk how but this found MY issue and fixed with a swap,due to no used ones to grab,and chose to do a whole unit.Maybe this will help isolate it.I have no idea how the hub got wacked but it was out about 1/8 on one spot,and tire wobble no noise.

Your brake hub may not be off, have you changed the rear brakes recently within a year? Just curious, drums when they start to wear out the internal springs will loosen allowing the shoes to shake and rub up against the drum, not constantly but occasionally. Just my 2 cents, but i'd do that check 87forever mentioned especially if plan on taking a trip.

Well I have changed the brakes about few months back drums seem to have no burs or odd spots I took the wheels off an the axles seem to spin with no odd feeling or play in them the part ware the drive shaft bolts to the hogs head is dry and no sign of leaking so maybe just a flat spot in the tire and not letting it ballance right

Ok simple thing is rotate your rear tires to the front.Then drive and see if problem moves to the front end.This will answer the ? if in fact it is just a tire issue and not the otherwise.Unless your drive line is a touch out of balance itself which in turn can create a vibration and or noise even with new u joints!I had a issue years ago new joints and carrier but driveline was out of balance.A shop that does driveline work can balance it to solve this low cost.Just some other ideas and also installing the driveline exactly back in the alignment at trans and rear (mark with paint) does make a difference.I have always did this before any trans work or dropping the driveline.Ok

thanks for the ideas i rotated my tires alittle wile back and also had them flipped on the rim itself cause just rotating them didn't help and i was sugested to flip them still no help...the drive shaft was took to the drive-line company to instaled the u joints and bearing and balanced and came back ok...wheels don't have any odd free play like wobble wise and no resistance just turning them by hand