3rd Gen: Pinion Gear or Something Else?

[Alex3rdT4R]

Hey guys, I'm new here and have tried to do some research already but I am stuck.

My new to me 2002 Toyota 4Runner 4WD Limited with 242,000 miles has a loud hum when driving at ALL speeds and doesn't change with my foot on or off the throttle. It was like this once I bought it. I had the truck on a lift and put in drive (2WD) and it still made the noise so I am assuming its the diff. However, I thought that if it was the pinion bearing, the noise would stop and start when pressing on and off on the gas? If it helps the diagnosis, I changed the diff fluid in the rear this weekend and it was black. Any help would be appreciated, thanks!

 

[Alex3rdT4R]

Could this be caused by a driveshaft not being greased? Will greasing the zerk fittings fix the issue?

 

[phattyduck]

You can remove the rear driveshaft and put it in 4H locked (FWD!) and see if the vibration goes away. Check the rear u-joint and double-cardan joint when you remove the shaft.

Could be driveshaft, pinion bearings or transfer case output bearings...

Rear u-joint is replaceable. The double-cardan is more difficult, but complete new shafts are easily available.

-Charlie

 

[kolelt]

How black was it ? Usually a cloudy grey color would indicate a bad pinion bearing in the fluid. Any shavings on the magnet bolt ? If you can get your 4runner into a shop and put it on a lift. Then put in drive. Guaranteed you’ll be able to pin point the noise. As there won’t be a load on anything and a bad bearing will definitely be screaming. In mean time try removing the rear drive shaft and drive it in 4H. If it doesn’t go away, it’s either the front , transmission or transfercase.

 

[T4R2014]

242k is a good diff lifespan. It's time for a rebuild.

 

[kolelt]

242k is a good diff lifespan. It's time for a rebuild.

Only if that is the issue.

 

[Alex3rdT4R]

Thanks for the advice, next time I am in the shop I will put it back on the lift to inspect and to put it in drive. Hopefully it is just the diff. The trans shifts very smoothly, and it engages 4wd H/L and locks the center diff very quickly

 

[dogtail]

Bad pinion bearing will hum with foot on gas or not. When mine was bad I found its sloppiness by putting in neutral, put E brake on. Climb underneath and try to push rear part of driveshaft at u-joint/pinion up and down. Bad wheels bearings sound a bit different but still have hum. Both the pinion bearings and wheel bearings can be bad and make noise without hand movable slop. Having a well balanced driveshaft with good u-joints will help your pinion bearing to hold up better.
You can jack the rearend and put in drive and pin point it that way to.

 

[Alex3rdT4R]

Bringing this back from a couple months ago.

Ended up changing all diff and the transfer case fluid. Noise is still present.

I had the truck up on the lift and put it in gear (both 2wd and 4wd) and could not hear the noise. The noise is ONLY present once the suspension is weighted on the ground and rolling.

Not sure what can be causing this, any thoughts?

Thanks!

 

[Wedgy]

I had the same noise and leaky rear axle seals so I replaced them and the bearings(which were bad) and still had the noise. Replaced the rear Ujoint and still had the noise so I bought an ARB rear locker and I installed it with the new pinion bearing and the noise is gone !

 

[Alex3rdT4R]

I had the same noise and leaky rear axle seals so I replaced them and the bearings(which were bad) and still had the noise. Replaced the rear Ujoint and still had the noise so I bought an ARB rear locker and I installed it with the new pinion bearing and the noise is gone !

Yeah at this point I am just going to wait on replacing the pinion bearing until I find an e-locker full rear axle and will just swap that in since the diff will have to come out anyway.