Got the dreaded rear axle hum

[gm350reratliff]

So lately I've been hearing this hum like a set of mud tires or a u-joint going. I was hoping it was just the tires cupping. Tonight I put it on jack stands and crawled underneath. Can't find anything loose so I put it in drive and took it up to about 45. Definitely coming from rear diff but I can't tell if its coming from the pinion or the driver side wheel bearing. Seems to make noise at both places. Without the rotor on, spinning the hub by hand it does feel slightly rough but I can't tell if its just the spider gears in the diff. Nothing leaking, nothing getting hot, just a noise (for now). Just about to turn 114k miles. I also realized I forgot to change the diff oil ever. I guess I will try that first. What's your take on it?

 

[4runnerAzGuy]

If it were me I would pull it apart and take a look since your going to change diff fluid anyway. Might be able to obviously see what the issue is.

Maybe someone has experience with this though and can give better advice.

 

[gm350reratliff]

Did a little more checking and it is definitely the driver side rear wheel bearing. So the next question is, does anyone have the FSM or link to repair this? Also, does anyone near Albuquerque have the special tool to press off the bearing? I feel like I should go ahead and replace the passenger side as well.

Another question is, how much time do I have before this bearing totally gives out and locks up? This 4runner sees anywhere from 20-350 miles per week so I need to plan accordingly.

 

[lehiguy]

Been there, done that

Mine had a bad driver's side rear axle bearing too. At first I thought it was the passenger side, look closely before you buy the bearing. It is pressed on, not really in the realm of doable in most people's garages, (I gave up and that is highly unusual). There is a retainer ring pressed on behind it which will need to be replaced as well. The bearings can be had for around $100 from sources like Rock Auto. Get a good brand, Koyo, NSK, etc. There are some garbage Chinese ones out there too. Removing the axle is easy enough, but you do have to disassemble the park brake mechanism in order to disconnect the park brake cable. Do yourself a favor and drill out or grind off the spot welds that hold the brake hose/hard line union to the backing plate. Put some bolts in its place. Then you can remove the caliper and set it aside without having to open the brake line. Take the axle and your new bearing to a shop that does that sort of thing. I paid a guy $50.00 and I consider it money very well spent.