So...after replacing calipers/brakes/pads (brake job) and getting new tires earlier this week, the tire-shop owner mentioned to me that he thought I may have a wheel bearing going out. I did know of a roaring noise, but I mostly just assumed it was a noisier vehicle than those I have had in the past.

I took it to a local shop mechanic's shop today and asked they diagnose it. They are known for doing good work but also expensive work.

They called me back, told me the good news was that my bearings seemed fine but rather that my rear differential is the source of the noise.

$3,000 was the quote because he said they don't rebuild Toyota differentials because he's had too many issues in the past out of the rebuilds. The $3,000 was a replacement from Toyota, but what he described to me almost sounded like a rebuild. I suppose it could be tomato/tomato.

I cannot spend $3,000 on a vehicle I only have about $13,000 in to begin with. I currently have 140,000 miles on it.

I figure my options are (which I'll probably be doing research on Youtube over the weekend):

1. Junkyard Replacement (I've done this in the past on a Chevrolet I had)
2. Rebuilt Myself (I've tried it before, not exactly thrilled at the idea)
3. East Coast Gear Supply (More on this below)

I'm open to any and all input. I'm considering taking it to a second shop to get a second diagnosis and quote.

ASSEMBLED 3RDS & CLAMSHELLS - 03-09 4 Runner

I've seen numerous suggestions for ECGS today while researching this. I think I need one of the two options in the above link, although I'm not sure what those are (unless one is a front and one is a rear differential?).

A buddy suggested it may be very prudent to change the fluid in that differential, both to clean-out whatever shavings I can as well as make sure the fluid is good and has proper fill. It may be too late for this to do anything regarding a fix but is there any chance at all that this may "fix" the issue?

If I hadn't just spent close to $1,600 I may be in a better mood to fix this but right now this is incredibly stressing me out. After I pressed him, the mechanic essentially told me that I shouldn't drive it until fixed.

I agree with your thoughts. What size are the tires? Is there any reason the diff would be stressed more than usual?

Are one of the rear axle seals leaking and so its out of fluid?

Youre certainly not going to make it worse by draining and refilling the diff fluid and its easy to do.

If you note its low on fluid or the fluid looks nasty it may give you information

-certainly a cheap option that I would do first.

Did the mechanic note exactly what was failing in the differential? Noise doesn't always equate to imminent failure IMO. Do you have record of the last diff fluid change? I'd start there and inspect the fluid that comes out and, while you're down there, verify that your diff breather is functional.

The front driveshaft at the tcase output is notorious for that u-joint wearing out. That would give you some noise in the front driveline.

How did he diagnose the front diff without inspecting the fluid or backlash? It seems a bit pre-emptive to make assumptions.

Start by draining and replacing the fluid. Since you know you are going to change it you can use really cheap 75W-90 from walmart. They have some real cheap options that people use to break in diffs before they drain it.

If you find really dirty fluid and large shaving on the magnetic plug then you have your answer. If you need to swap the diff I recommend buying a used one and swapping in. car-part.com or lkq junk yard website is a good start to find a used one.

If you are worried about hurting your diff in the mean time you can pull the front driveshaft and turn on your diff lock. This will keep it from driving and instead would just be turning with no load applied. (I assume you are an AWD V8?) If not disregard my last thought.

It would be helpful to know the history of your T4R. I am suspicious of the rear diff diagnosis. To find a bad rear diff you usually have to drain the gear oil and take a look at it as randy88 suggested. Did your shop do this? I would not spend any money on a replacement diff until you find out exactly how your shop determined it needs replacement. The rear diff in these vehicles are not the strongest diffs for the weight of the T4R. It is an 8 inch ring gear that started life in the original small pickup, but are an OK diff if you don't abuse it. Are you towing heavy loads? Trail riding in difficult terrain? These conditions will definately shorten the life of that 8 inch rear or make it fail completely. I have replaced my rear wheel bearings but my rear diff fluid always looks clean when I check it (regularly). If you are just using you T4R for normal street driving I doubt your diff would be failing. I would guess that it is more likely the rear wheel bearings. The rear bearings are not an easy fix. There is a special press tool and a 20 ton press you need to get that job done. I am a little handy when it comes to things like that and had welded up my own press tool and I already have a 20 ton press so I do know of which I speak. Just trying to help you find the cause...Take your T4R to someone who knows Toyota's. Not the stealership! There should be a decent 4wd shop around you. Get a second opinion. Please keep everyone up to date on what it turns out to be, thanks.

I think I've decided to purchase from ECGS one of their rebuilds. I've read so many good things about them and will be calling tomorrow for them to answer a few questions hopefully.

Toyota V6 8''- Pickup, 4runner,FJ Criuser

On my door jamb, I found this: A01A/A750F. I think that means I have a a 3.73 ratio (2007 4WD V6 SR5 Model). Does anyone disagree?

I think on ECGS, I need the following options:

ABS Diff (Unsure. I have ABS, not sure if I have a sensor on my rear differential. I tried looking last night, I didn't see anything that looked like a sensor going in but I couldn't exactly see up top. Does anyone have a clear photo showing 100% exactly what I'm looking for?).

3.73 Gear Ratio (as discussed above)

Solid Spacer (My understanding is that this better and theoretically makes it easier to not screw up during installation? I don't mind spending the few bucks if it is indeed better in any way).

Add Gear Oil (Unsure. I assume this means they are sending you the oil for install? I'll discuss this with them on the phone tomorrow. If they ship something quality then why not, would be more convenient but is the $40.00 overpriced for this?).

Select Flange Style I think I need a used flange specific to my vehicle, correct? I don't have an 04 or older 4Runner, I think my gear ratio is less than 4.56 (this should knockout the double drilled flange) and as far as the harmonic flange goes, I have a 4WD and it insinuates that this one is mainly for 2WD vehicles. This is something they should be able to answer for me.

I won't be adding any lockers unless someone can convince me it's totally worth the money. There are so many options here, some totaling a minimum of $1,195. I am, however, interested in how something like the spartan locker works. I don't want to fool with running electrical or air to my differential, but I'm curious how some of these options work. Are they locked full time? Are they mechanically initiated one way or another? I'm all ears.

So, I ended up ordering from ECGS. After discussing with them, I feel confident I have a 3.73 ratio, no ABS on the differential (that was on older models), and will use a used flange that matches mine.

I know I'll need 3-4 quarts of gear oil, anything beyond Lucas recommended? I know I'll need a gasket, should I use the paper one Toyota species or something silicone (ECGS stated that they use silicone)?

What else will I need on hand? Plan on purchasing what I can from Advance Auto as I have some credit and probably a coupon.

Use the gear oil ECG recommends, it's definitely not Lucas.

Well, the shop I took it to is known for doing quality work in town. They generally have a reputation for being a generally trustworthy...although not cheap...mechanic shop. I took it to the shop and simply asked them to put it on a lift and tell me which/how many bearings needed replacement. That morphed into this. I believe one of the methods used was a stethoscope. As far as my 4Runner goes, I don't tow or off-road in it, but I also never personally checked the fluid. It currently has 140,000 miles on it. I did research the rear bearing and feel much better about replacing the 3rd from ECGS than I would doing the bearings.

I will personally try to diagnose further the issue personally, I can check the fluid and magnet.

Well...on the ECGS...if you add $40.00 worth of gear oil to a purchase...they ship you 3 quarts of Recommended 85w140 Non-Synthetic Lucas. I am however open to using any fluid reasonably priced.

Lucas 85w140 Non-Synthetic Gear Oil

I stand corrected!

Did you check the fluid and plug and/or get a second opinion?

I had very similar symptoms on my car and a new rear dif from ECGS solved it. No problems so far with 20k on it. I use their recommended gear oil


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I had the same issue. Took it to a specialist (they only do differentials and nothing else).

They told me the case sub-assembly (#41302 in this diagram: Rear axle housing & differential. 2003 Toyota 4Runner | Toyota Parts Direct, London ON) in 4th gen T4Rs is notorious for premature wear because the bearing inside diameter is too small for the amount of power being delivered.

Sure enough, when the took it out, the bearing slipped off on its own.

He replaced the whole assembly with one from a Tacoma that was noticeably larger, but re-used my pinion and ring gears in order to keep the same ratio.