NEW TSB, Whine Noise From Rear of Vehicle

Thanks for this. Gotta stop by and get er done.

 

I will be curious how the dealer will handle my truck. I had the rear diff replaced around 12k ago and there is still a slight whine
at times. I guess I will stop in to see what happens.

 

My 18 has what i would call gear whine when feathering the throttle.

I noticed it right away but it doesn't bother me since i know what it is. The 4.30 ring gear is big and some resonance is to be expected. That and the fact that there's really no isolation between the pumpkin and suspension, i totally get why the noise gets transferred to the cab.

My mustang had a silent rear end until i swapped bushings. Sure enough, same whine under similar conditions. There's nothing wrong with the pumpkin, just the fact there's no isolation.

Based on the TSB, it looks like toyota engineers believe the back corner of the cab is where the noise intrudes into the cabin hence the insulation and new cab mount bushing thing.

Unless mine gets substantially louder over time, i'm not bringing it in. But I will hold onto the TSB for reference.

 

Just called and left a message for my service adviser to get this taken care of. I have had mine documented a couple of times, so hopefully he will just order the parts.

 

I had a clank from the front of my truck. Dealer just fixed it for me. Turned out the skid plate was bent and hitting the frame. Just something to look at.

 

Thank you I will look into that.

 

Nope. Rear end is going to explode. Ask any arm chair mechanic....they’ll tell you the same.

They’ll also tell you that mechanical components aren’t supposed to make ANY noise....oh, and your resale value is going to plummet because of this.

If you think I’m kidding, next time you need to drop a deuce sit down and cozy up to the howling rear end thread. Wade thru 200 plus pages of doom and gloom.

 

I agree. Hopefully the TSB will fix the howl and this won’t be an issue anymore.

 

It’s not going to “fix” the howl.

The point of the tsb is to reduce resonance and deaden what Toyota considers a normal operating noise from the diff so we don’t hear it.

 

I agree.

Poor tolerance on the set up plus resonance into the body creates the howl I can hear. Once the gears are worn in and set they’ll howl their entire life. I don’t believe they’ll blow up by any means but a properly set up r&p will make very minimal noise. I’ve personally set up a few rear ends.

But if I don’t hear it anymore I’ll be happy.

If when I sell the truck the person test driving it doesn’t hear the howl they’ll also be happy.

I have a fairly high tolerance for noise but...

I would have never purchased this truck if it howled this bad and I’m pretty sure no one else would either. Hence my comments of diminishing value.

I would have just bought the other Tacoma that didn’t howl.

 

Several reports here of them being examined with proper backlash and tolerances reported. These guys build 17K of these a month, not a couple. Pretty sure setup is the first place they looked.

 

You’re right. I’m sure they have been checking it. Who’s to say they aren’t out of spec. Toyota hasn’t. The only official diagnosis for me was a bad pinion bearing and that seems to be false.

The noise is apparently hit or miss with these trucks so I’m just guessing there is a tolerance issue here. Certainly sounds like badly set gears.

As far as I can tell you can’t buy a stock gear ratio r&p without having to buy the whole third from whoever Toyota is buying it from. Might be a quality issue too. Who knows.

If this TSB doesn’t fix the issue, I’ll certainly give it a go but I’ll wait until a third party offers gears, like Yukon.

 

Personally, I think the tolerance problem is the contact point of the spring/differential. Something in the spring wants to conduct and amplify the natural diff sound. Every gearset makes noise. In some of these trucks (My first one) that sound is being transmitted through resonance. I think this TSB will accomplish the job. We will see. My new truck makes no loud sound at 4K miles.

 

There might be some sound amplification occurring too.

The resonance might be making the sound sound worse than it actually is.

So I’m hopeful that dampening will at least make it less noticeable.

Again I’m not worried about the thing grenading.

 

Ah yeah. I was just typing that.

You probably won’t get it then, hopefully.

My first diff did it at 2k and it was barely noticeable; second diff has been crazy loud from mile one.

 

Yeah, I know exactly what a gearset sounds like when it is getting ready to grenade, and this little whine when feathering the throttle is not it. Drive me batshit crazy but it wasn't going to fail.

 

Oh yikes. I’ve never been that far but I did try and go cheap by buying used gears once... I sure thought they were going to explode but after tearing back into it everything checked out. I swapped those gears out as soon as I could.

That’s how I learned that once gears set there is no unringing that bell no matter how well the pattern looks.

 

The last rear diff that I had which seized (old Chevy) many years ago started out sounding exactly like what my Taco’s howling sounds like. But, the difference between the two is that old diff got progressively louder and to me mine has stayed close enough to the same that I’m thinking it’s safe. I may be wrong. I hope I’m not. I’ve stayed silent for a while over this issue because I said all along my plan was to wait as long as I could on a fix. The date I had in my mind was this spring. If a fix was not out I planned to quickly LL my truck and be done with it. If this TSB works then I’m good to go and all is well. Gears make noise but these make more than they should, or we are hearing more than we should. In the end, I’m happy to have a fix and I hope it is truly a fix and that the diff is not in any way damaged. I think all should be well and hope we are all happy as Larks by the summer.

 

200+ pages is a lot to go through for people stumbling into this thread. For the sake of clarifying what my truck had and what the tear down revealed, I'll recap it here.

My 2017 OR AC had the howl. After I trained my ear to hear it, I could pick it up quite easily as well as pick it up in other people's trucks. I opened a case with corporate and had my truck checked out by the local dealership. I was told at the dealership that they had replaced a few third members in both second and third gens and the sound always came back. They were the ones that pointed me to the TSB that covered the issue for the entirety of the second gen run.

We have a company mechanic and I have a mechanic for my personal diesel. I had both of them listen to the howl and to my surprise, they both opined that it was "just a noise". That "all rear ends make noise" its just to what degree we can hear them or to what degree the manufacturer muffles them out.

While I took some comfort in this, I was still concerned. Around the same period hiPSI and I exchanged PMs in which he pretty much postulated what both my mechanics said.

We do a lot of crawling (for various reasons) in our Tacoma and with the suspension and wheel/tire mods, decided to go with the 4.88 gears. We are lucky that a fairly nationally renowned rear end shop is about an hour away. We selected our setup and made an appointment to bring the truck in.

I have withheld the name of the shop at the request of the manager. Apparently someone else on a forum named them and they were inundated with calls regarding the howl.

Anyway, I did a ride along with the foreman and he immediately heard the howl. To my surprise he shrugged it off and began stating all the vehicles manufacturers and models with noisy rear end setups. The bottom line was this, the nature of the noise was not indicative of anything other than what he referred to as a NVH issue. I asked them to do a tear down of the old gears as part of the work. They charged me a nominal fee. I left the truck there for two days and returned.

The manager had the old set neatly laid out on an old canvas tarp in one of the storage bays. He proceeded to walk me through the condition of the gears, what they looked for as they were removing them and gave me a fairly detailed outline of what we should have seen at this mileage if there was an issue.

There was nothing of note. Everything was fine. The noise, he said, was due to the nature of the gears, the set up and the NVH characteristics of the truck. Calimed that he's had quite a few tacoma owners come in over the years worried about similar noises, but that the hino rear ends were fairly stout. He said that there was nothing in the setup or the condition of the old set that would have indicated a problem that needed to be addressed. He asked me if I had noted an increase or decrease in the noise depending on the number of passengers, there load in the back, the gear I was in etc. I told him I had not gotten down to that level of scrutiny. He also informed me that the V8 4runners and Lexus GXs were infamous for having a similar resonance that was addressed through a TSB.

Here's the bottom line. I've heard a lot of theories on what this may or may not be. For awhile I was seriously convinced my truck had a problem. After talking to some people who wrench for a living, my fears abated a bit. After talking to someone who sets up rear ends for a living over a wide variety of vehicles and having been taken through a teardown, I would have had no issues keeping the old gears in the truck and not spending another minute worrying about it.

As a hobby, I breed several species of snakes and dwarf varanids....some venomous some not. I've been in that hobby for over 40 years. I have mentored other venomous handlers at both zoos and at veterinary schools. I have consulted with the setup of certain species at zoos and museums. I do lectures and have been cited in scientific literature. While I do not consider myself an expert at anything, I have sent a lot of time working with several specialized species and have a fairly accurate ability to work with the animals both in regards to behavioral issues and in regards to their overall captive well being.

I am also a member of several snake forums. Not a day goes by where someone who claims to be an expert in the field spouts off about something I patently know to be bullshit. I have seen people given advice that probably caused them countless worry or that probably resulted in potential harm to the individual or the animal.

I am well aware that forums in general have given rise to a new breed of experts who have received their knowledge form "Google". They are experts only in parroting what they read on other forums or in various online articles.

nDub, this is not directed at you, but in general this thread has been littered with the opinions of people who arrived at their "knowledge" in a similar manner. While I personally think there may be several things going on with these rear ends, the non-intrusive howl at certain speeds is a resonance issue. Those with noises that are completely invasive and spread over a wider range may have something else going on....but for what I experienced, I can positively attest to the fact that there were no issues with my rear end other than resonance.

 

Well written.

My experience with gearboxes started long before Google and almost before the internet lol.