Hello Everyone,

I have a 1997 4Runner, 272,000 miles, 4WD, AT, 3.4L I purchased about a year ago. Just ordered all the bushings to do the front upper/lower control arms and new oem Toyota LBJ’s. I also replaced the engine when I first got it due to failed cylinder #2. So im now getting the rest of it in order.

I have a rear end humming/whirring at 30-50mph I am trying to diagnose. Becomes more audible when you let off the gas and coast at these speeds, you can even feel a very faint vibration. Seems to be it might be the rear diff/3rd member. I did replace the gear oil when I first got it, still topped off and not leaking. But I’m also worried the rear driveline might be part of the issue as I get a clunk whenever I first start driving after the vehicle has been sitting.

I considered road noise from newer cooper AT3’s or wheel bearing. But no play in the wheels and I’m still getting this coasting noise when the car is in the air, see videos.

At this point I am considering getting a used 4.10 3rd member from B&R and replacing it. And possibly also having my rear driveline spider bearings replaced and balanced.

I’m hoping someone can help conform what I’m thinking from the description and video. I don’t think this noise is normal and I assume it will only get worse if I leave it.

4Runner rear noise2:
[IMG]YouTube[/IMG]

4Runner rear noise3:
[IMG]YouTube[/IMG]

Thanks.

Im going to take a stab at this for you! For one your ring gear and pinion are more than likely still good. (This is the good news). Im thinking youre going to need to replace your pinion bearings. However, If you take out your 3rd member and you see a lot of material worn from the pinion and ring gear and if there is a lip that you can feel with your fingernail, your gears are too worn out which means you probably have excessive backlash in this case also causing a loud noise on deceleration. To sum it up, either pinion bearing or ring gear and pinion are too worn. First and foremost you need to go ahead and drop the 3rd member and when its out of the truck on a table or bench you need to roll it over yourself and pinpoint where your noise is coming from.

Thanks for the advice. im getting a used good 3rd member coming with much less miles to swap it out. I dont have experience rebuilding these so dont want to take my chances. and a used one for $250 is worth a shot.
If the original gears are ok maybe ill take a stab at it, but i also cant be without the rig driving for too long.
Hopefully the replacement part does the trick, but i will report back once its done.
Thanks.

I had an ARB locker installed and they forgot to torque the carrier bolts. it made a strange kind of tire road noise whirring sound to it. it's hard to get sounds from vids but maybe I think mine was very similar to yours. also very similar speed range to what you report. I drove on mine like this for quite some time.



and here is what I found when I pulled the 3rd.



sounds like your doing the right thing and just grab another 3rd. I have now replaced the bearings in one and have about 5K miles on it. it was not hard but very tedious and it took me 2x crush sleeves. you don't really need any special tools but the learning curve is steep.


2 cents on the shaft

I would also suggest since your going to the trouble? just grab a new rear driveshaft. if you have a good driveline shop local just have them make you a new shaft. probably cheaper in the long run. driveshafts do wear out and that front double cardan joint sucks.

I have found the clunk is from the slip joint being worn and your 3rd member not having the correct backlash.

At about 225K miles my e-locker rear diff started making a little whining noise. About what you describe. I'd have probably ignored it a bit longer but I got lucky and found another locker third member in a PnP junkyard. $50 SCORE!! So I swapped that in, noise gone. The one I took out had great looking ring and pinion gears, no problem at all there. And no unusual gear lash either. But the pinion bearings, although they were still snug and had no perceptible slack, just had a faint bit of 'noisyness' to them, they'd just rumble ever so slightly when spun. And the flange felt noticeably easier to turn than the replacement, too easy.

I figure if I ever have any other issues with a locker diff (my wife also has an e-locker 3rd gen) I'll just haul this one off and have it rebuilt, and do a quick swap again.

PS: Me later figuring out I'd swapped a common 4.30 locker for my original rare 4.10 locker... that's a different story...

I had the pinion bearing go out on a Toyota 4WD truck rear diff, and that noise fits your verbal description.

Thanks for the added confirmation! Sounds like my pinion bearing is going out..

So i do have used diff and rear driveline coming for $325 together. im thinking of getting the driveline serviced locally (balanced and spider bearings replaced) for piece of mind.
And B&R says they full inspect the rear diffs so hopefully its good to go but worst case ill have one out i can get serviced.

Will be interesting to see what i find on the 3rd member once i pull it, never would have thought loose bolts.. ill report back hopefully in a week or less.
I did do the spin test i was so worried about getting the correct ratio.

Thanks!

I was preparing for some sound deadening today and removed my rear seats and cargo area carpet. Went for a quick drive in the mountains and when I was back in town going slower I noticed a whirring that had literally just cropped up (wasn't doing it on the way up the mountains or even on the highway back down). Almost sounds like something getting turned on a lathe or perhaps even a jet turbine noise. Changes pitch slightly when coasting vs accelerating. Is this likely to be my pinion bearing. How long do I likely have if this just cropped up to take care of it?

If you just noticed this after removing the rear seats and carpet then it's probably been like that for a long time and not excessive. Rear diffs will make some noise during operation so it's likely that you can just hear it better now with that stuff removed.

The weird part is I only heard it a bit after driving around like that for a bit. Maybe it needed to warm up to make that noise, I suppose I'll find out when I get home.