Intermittent Rumble in drive train - rear bearing replacement did not fix it.

Both of my front bearings went bad recently and I was getting a similar intermittent rumble sound from somewhere in back... sounded right rear. At 125k miles I presumed it was yet another wheel bearing.

So I replaced both rear bearings.

That didn't fix the problem. I'm still getting a rumble.

The rumble sounds exactly like the bad front bearings did, except toward the back: A half second pulse every couple seconds. Sounds like someone's tooting a Tuba in the room next door.

Could the problem be in the differential? A bearing there perhaps? Or one of the drive shaft swivels?

Does that sound seem like what you'd year from a bad bearing inside the differential?

How can I go about diagnosing the actual source of the problem?

Thanks much.

 

Could be carrier bearing possibly or even the pinion bearing(which would be my initial guess) can recreate it by giving it a little gas and changing the pinion angle. Check u joints also.

 

It is very possible.
The first on that seems to go is the pinion bearing.
But it’s not important for carriers to go if the fluid wasn’t maintained.

 

How would I diagnose or rule out each of those three problems:

1. carrier bearings
2. pinion
3. u-joints

?

 

Yeah, I didn't replace my differential fluid until 100k miles. Now I'm at 125k and the problem has popped up. Fluid was real clean when I drained it for the bearings job.

How could I diagnose the problem between the pinion bearings or the carrier bearings? Or should I consider just replacing both?

This rebuild kit from Rock Auto has both bearings.

But I'd like to figure out whether this is really the problem before dumping 2k into it.

 

Get it up on jacks and listen with a stethoscope

 

If it’s bad enough you can disconnect the drive shaft and feel for play.
Sometimes it’s not bearing, but the crush sleeve.
And to check that, you really need to pull the 3rd member.

I’ve only been involved in a few rear differential rebuilds.
And then, I was accompanied by someone that knew what they were doing.