Low, flat hum from rear at 145k. Dealer says replace rear diff

This is partly to ask for advice and partly just to rant/vent about dealing with shops.

My '08 (5.7L 4x4 SR5 DC 145k) miles suddenly presented a very distinct (for me) low hum from the rear.

The noise comes on sharply at ~28mph and continues consistently until it steps up in intensity around 68mph. At that point, it noticeably loudens with speed and can gradually be felt in the floor. It does not change with side-loading and has minimal, if any, change under accel/decel. The noise is low volume, 'flat', and consistent, so it understandably blends in with the background.

The rear diff oil (40k old) level, color, and consistency were fine.
To rule it out, I DIY'd the driveshaft carrier bearing and U-joints. No change.

I started calling shops, assuming it's a wheel bearing or possibly the diff. It quickly became evident how difficult it is to get an estimate or competent conversation. Half the stops (including dealers) wouldn't/couldn't give a quote over the phone - "we don't know what type of axle it is".
From my perspective, that shows inexperience, and that's easy to look up by VIN, no? It's not like Toyota had a myriad of axles like Ford.
I need to 'bring it in for a diagnosis', from $150-250 for "1 shop hour" to 1/2 day.
My takeaway was a large liability for it to turn into a wild goose chase at my expense. At that point, I dismissed them as not being qualified. Am I wrong for this? I'm not trying to be difficult but looking for an ESTIMATE! Such as - IF it is the differential, then what?

I ultimately took it to a dealer that told me what I hoped to hear: "should just take a few minutes to know if it's a wheel bearing or a diff. We'll put it on the lift and use a stethoscope."
YES! THANK YOU!

I drop it off expecting ~1/2hr of confirmation, then proceed with wheel bearing replacement.
~$1000 to fix the noise and I'm a happy camper.

The exact thing happens that I was worried about. "We've done 3 test drives with 'chassis ears' and put it on a lift with a stethoscope. We're overbudget for a diagnosis and we can't hear the noise."
You can't be serious!

I go back and test drive with the master mechanic. At 30mph I point it out - "oh, right, yeah I hear it". At 70mph, it's impossible to miss. He even comments 'you can feel it in the floor'.

They drained the diff and 'used a magnet to find larger metal flakes than normal in the fluid', according to the invoice. The noise is now ~10% quieter, so I guess that is some confirmation it's the diff, but not certainty. They quote me $4k for rear diff replacement, as rebuild cost was even higher, and parts are backordered until unknown.

I then call an "axle and transmission specialty shop" recommended by an indy shop. They need to do their own diagnosis, for another $200, despite Toyota already having done theirs. They have no idea what type of axle the truck has, claim they cannot look it up by VIN, and will not discuss price without their diagnosis.
I understand trying to be thorough, but I just cannot continue this $200+ 'price of entry' just to get a ballpark estimate.

What are my options here? Used/new replacement, rebuild? What type of shop should I look for? What questions should I ask?

 

I'm just gonna shoot straight. You seem to be a difficult customer. You want a problem diagnosed, apparently for free, and then question the outcome because it's at odds with your opinion? I get it to a point. 145k on a rear end is not much unless you tow a lot. Or do burnouts. Do you?
According to you, they found excessive metal in the fluid. What more confirmation do you need that it has an issue?
Your options are new, used or rebuilt. Pick a reputable shop and go.

 

If you wanna do it yourself, you can replace just the third member pretty easily. Hardest part is finding one. You have to pop the axle shafts out to do it and at that point you're a brake hose and parking brake cable away from fully removing them and dropping them off at a shop that can press on new wheel bearings.

 

I'm guessing a bad pinion bearing. Was it run low on fluid?

 

I wouldn't worry about it until it got worse. I worked for a glass company that had an 88 1 ton Toyota pickup. Over the years (probably at least 15) the oil leaked out of the rear diff. It just got noisier and noisier. It finally got to the point where you could feel the slop in the ring and pinion gear. I found a used 3rd member in a junk yard and had it swapped (use the lower geared 4wd one since it struggled at highway speeds). The shop that swapped it showed me the old one. The teeth on both the pinion and ring gears were worn so badly there was more than a 1/4" of play (it should be something like .008"). The ends of the teeth were sharp points.

For the most part things like a axle bearing just starting to go bad or a u-joint aren't going to suddenly fail and cause major problems either. But as they get worse it'll be easier to figure out where the problem is. You can try draining and replacing the oil in the diff. You could even use a thicker grade gear oil to see if the noise/feeling changes. I would crawl under your Tundra and check to see if oil is leaking out (most likely you already looked) and check the cap on the breather to make sure is can be spun freely. The breather caps get plugged up and that can cause issues.

 

I'm actually not a difficult customer, but I do appreciate you felt the liberty to say so.
Maybe to you, anyone that doesn't write a blank check with no questions asked is a 'difficult customer'?

I don't argue, I don't nitpick, I don't change the agreement after the fact, and I don't negotiate the price. I explain my situation and ask for a quote. As far as I'm concerned, the price is the price. I may ask a few clarifying questions (almost always along the lines of "when can you start?"), but if I don't like the price, I say 'thanks' and move along. For example, this dealer did their 'multi-point inspection', without my request, and quoted me $1750 for a radiator replacement and $4500 to fix the leaking front timing cover. I felt both of these quotes were astronomical and absurd, but I just simply said "thanks for letting me know" and re-aligned the conversation to the rear hum noise. Nothing more.

While not being a bubbly social butterfly, I strive to be very pleasant and non-argumentative. Which is why I bend over backwards and try to be thorough and do my due diligence before hand - to avoid any misunderstandings or 'episodes' after the fact.

Nowhere did I say I expect a free diagnosis. What I did try to articulate is that if I'm paying $200+/hr, I expect to get a plan backed by experience - not a shop that has never worked on this model before and is happy to 'figure it out' at my expense.
I'm looking for "oh, yep, I know that one well. It's either a 9.5 or a 10.5" rear. It's usually the pinion bearing, but I'll have to put it on a lift and taken a listen to know for sure." Sure! Take my money, happily.
At a rate of $200+/hr, I don't think it's unreasonable to expect a certain degree of performance and experience, especially from a shop that specializes in differentials.

What I'm trying to do is evaluate if that shop is competent and I don't appreciate them making it difficult to do so by not entertaining basic conversation. I don't have the time or money to drive all over town, dropping my truck off for 'diagnoses' at $200/pop just to start to have the conversation about rebuilding the rear end. I don't want to be $200 over a barrel just to know they're clueless or incapable.

 

Thanks for the reply.
Not that I know of.
I got the truck at 80k and replaced the fluid soon after. I replaced it again at ~110k.
Neither time was suspicious.
Recently, when I checked the fluid, it was easily felt with the tip of my pinky finger.
The dealer also made no [negative] comment about the level when they did the drain & fill a few days ago.

 

I guess I can keep this in the back of my mind.

Is anything going to get worse by continuing to drive it? The bad bearing will continue to gradually shed metal shavings, which will mostly get caught by the magnet. I guess drive it until the noise is unbearable?

 

If a shop gave me a rough quote on a guess over the phone... I would avoid that shop entirely... They are likely the type to parts cannon shit until you give up financially or take it to a competent shop...

Also, when you call a shop, you are not likely talking to an individual that really knows about cars. They just take the calls and follow a general script. That $200 diag is what gets you to talk to the mechanic.

To add, no shop should accept the diag of another... I wouldn't if you brought it to me. I would take the hour to confirm the diag.

I would look for an independent shop in your area with a history working on Toyotas. Pay their diag and chat with the mechanic about the concerns and let them do their job.

Finally, I feel you here and your experience is partly why I moved to doing my own diag and work. But at some point you need to give some trust, just a bit...

The competency you are looking for does not live in this society anymore. Smartphones and social media are stupifying the population into complacency with laziness.

 

I appreciate your response, but I have to push back a bit.
First of all - "If a shop gave me a rough quote over the phone...I would avoid that shop entirely..." - come on, you're just being contrarian.
For rebuilding an engine, transmission, or even a differential, fine. For pretty much anything else, stop being difficult and just give me the quote.
Again, it's a quote, an estimate. I don't need to know if it's a difference of $1,000 or $1,050. I need to know if we're talking about $800 or $3,000.
No matter what happens in the diagnosis they're just going to the book to generate the quote.

I called a few other shops to ask them about the differential. I asked about the radiator while I was at it, mostly for curiosity since it's a DIY afternoon project. "Usually we need to see it first...do you want to drop it off for a diagnosis?" "Erm...no, it's just a radiator, nothing special". There's nothing to diagnose. There's nothing to look at. The radiator has a leak.
To me, that just screams an unexperienced shop. And yes, this particular interaction was a perfect example of getting someone on the phone who knew nothing about cars. Doesn't really help their case. Just makes things more difficult and more likely to get upset.

I later found a differential rebuild shop on the outskirts of town. I got the exact guy on the phone I was looking for. "Yep, 10-five rear end...third member, rebuild runs from $2000-3500 depending on if it's just bearings or the hard parts are damaged."
That's all I needed to hear. 30 seconds on the phone and he distinguished himself from all the other shops by miles.

 

$4k for a new rear differential replacement or up to $3500 for a guy to replace some parts in your old one.
If I couldn't replace it myself, I know what I would do, but hey you go with the guy that told you what you wanted to hear over the phone.
I hope it works out good for you either way.

 

I was somehow mistaken!

I'm not sure where I got $4k from. Maybe the service advisor said it over the phone and I misunderstood.

I looked at Toyota's diagnosis report, which has pricing on the last page, including the $1750 for radiator and $5000 for the front timing cover oil leak, but I can save $1000 in labor on that if I do it at the same time as the radiator

3 options provided. $7400 for Toyota to rebuild it, $5500 for a new replacement, and $5100 for another option I'm not sure what the difference is.

Either way, the new replacement is backordered from Toyota until unknown.

But thanks for continuing to be helpful!

 

Might be worth trying to find a low mileage wrecked truck and just swap the entire axle if you can find one close to you.
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