Well, I finally took my 4Runner into the shop today. The road noise was unbearable. From 5mph up, the whir would start. Makes the noise while in neutral and when decelerating. Online research suggested either pinion bearing or carrier bearing. After inspection it was determined that it was 1 of 3 things, which by the way, are all costly. 1) Front Pinion Bearing=$835+tax 2) The 3rd member assembly=$1,358 3)Axel Bearing=$921!!!! I am currently waiting for the tech to call me back, but they are going to have to open it up to fully determine what's going one. The tech is leaning towards the #1, which is most likely the cause. The fluid was changed 30K miles ago with Mobil 1 diff fluid. The plug had no metal on the end when changed last year, so I doubt the 3rd member assembly will be required. The dealership admitted that there hasn't been hardly any cases of this on my gen 4Runner. It has never towed anything in its life, but parts are parts, and they will fail sooner or later. I am just glad I am getting it taken care of before a possible diff lockup, which could cause either a wreck, or destroying itself and doing more damage. Sucks because I have no truck for a couple of days. I don't have any extended warranties, and this is the first major issue to arise. Also forced to take it to dealer, many people wouldn't touch the thing. Said Toyota's setup is too complicated (granted I live in MS...) I will keep everyone posted.

Thanks for all the replies guys. Well, just thought I would let you know it was the first one, costing $889 out the door. New bearing, gasket, and seals etc... Anyways, hope this helps for anyone else having this loud roaring noise!

That sucks. Surprising no indy shops would touch that. Plenty in my area would hav no problems working on that. Have you owned the 4Runner since new? Just wondering if there has been other owner(s), that might have been a factor, too.

w/ p pnut

Any idea how many times the diff fluid was changed?

I am the second owner. From what I can tell, it had one owner, which was in Houston,Texas. I purchased the car in 2007 with around 93K. I talked with the mechanic, and he showed me the own bearing. Sure enough it was pitted, and he said that water had entered the axle bearing and wrecked havoc on the pinion. Luckily, it was only the front pinion bearing and not the axle bearing. He removed the rust inside the axle, cleaned it up, and checked the axle bearings (they were ok), but resealed them, replaced diff gasket, fluid, and seals. Everything checked out ok, so no new 3rd member. I have never taken it on any serious trails, and it has never towed anything in its life. Doesn't make much sense, Carfax came out ok, but who knows. Doubt it was wrecked, can't tell the signs, but they may have done something stupid to damage the seal early. It was worth getting fixed because now it is so quite. I can't even tell I am driving. So nice! All I need now are some new shocks and I will be good to go! Also, doubt the diff fluid had been changed at all during it's first 100k. I changed it around 100K with Mobil 1 75-90W, but one the invoice I noticed he put 80-90W in there, which was interesting.

The water makes sense... The OE vent system stinks IMHO. Click the axle vent link in my sig for more info.


Glad it worked out and you're enjoying it again.