I have a 99 blazer 4x4 it is humming in he rear end we had the rear bearings n seals changed new diff cover new fluid and it is still humming what is it??? PLEASE HELP!!!

ok does noise change when turning left or right if not its not a wheel bearing next try putting in neutral at 55 does noise change what you are looking for these is pinion and carrier bearings in differential the noise can be coming from several places have you checked all your fluid levels front and rear diffs and transfer case also check fluid condition also check for metal in fluids if you stick finger or paper towel in and if you see metal you will know where your noise is coming from

If its a 4x4 remove rear drive shaft from vehicle, remove large nut (pinion nut) at front of diff which is generally hidden when driveshaft is in place. with a bearing puller remove pinion bearing replace with new one, install new pinion seal reinstall pinion cover and pinion nut tighten to specified torgue reinstall driveshaft check diff oil for proper amount

first swap to a front tyre to eliminate that issue


new bearing shouldn't be rumbling
to get the bearing square on and home
did you use a press to fit the bearing to the rear axle
or tube method ?

and did the seal kit have this nifty plastic seal fitter so axle didn;t rip the seal surface

have you check fluid level and it might need to be change and put new fluid and additive to diff

first remothe the diff cover and drain, find the bolt that retains diff gears and remove then remove pin holding the diff gears, at this point do not rotate any part at all, axle or crown, push axle inward and remove c clip holdin axle in, pull axle out and using a bearing puller remove bearing, lubricate new bearing and install using new seal, examine axle for damage to bearing contact surface is good install , reverse procedure to finnish and fill rear end with new oil

this is very hard if you do not know what you are doing. Ill try to step you through this

• pull wheels
• drain pun-kin case
• pull rear cover
• in between the spider and axle sets pull C ring with needle nose pliers
• pull hub and axle out CAREFULLY as there are roller bearings on the end of the axle housing
• pull seal out at the end of axle housing
• tap in new seal CAREFULLY and straight DO NOT BEND IT or it will be junk
• replace axle carefully as the roller bearings are still there
• replace C clip to original position
• replace axle diff cover and replace the gasket with a new one
• refill diff case
  
• install tire
• your good to go
  

Hi, there, Check your break pads. Could be from there.
cheers

That will be a Huge job. The whole front diff must come out of the car and the case will need to be taken apart to even gain acess to the carrier side bearings.
The hub bearing is where the wheel bolts up is that maybe what you are talking about?
Also the axle seal isn't that bad to do you need to remove the cv shaft then it's just a simple remove the seal and install the new one.
But all of these jobs will be big ones.

4x4 actuator may be bad. its has an elctrical switch. this is the part that pushes your front drive shaft forword to engage the front diff. it also may not be aligned properly. You should also check your transfer case fluid level and the front diffs fluid.

Sounds like the front hub bearing assembly.