3rd Gen Poll: Rear End Noise howling when feathering throttle

Your 2020 has the TSB materials from the factory.

 

Yeah I should hope so, Toyota. Thanks for confirming.

 

I replaced my rear leaf springs with a new non-OEM pack (new shocks too) and do not have the noise anymore. Had been made quieter by the tsb leaf pack “dampers” but it’s gone now.

 

It would follow with Toyota's logic in their TSB. They're saying the noise is originating from the gears in the diff, taking a sound path through the axle tubes, up through the leaf springs, frame, and into the cab through the cab mounts. That's why they replaced leaf springs (although I don't know if the design is different on the TSB ones?), and added dynamic dampers to the cab mounts.

If adding a bunch of sound insulation behind the rear seats was the answer they probably would have done that instead as it would have been cheaper than replacing leaf packs.

 

Very interesting. I've also read that spraying fluid film on the springs has eliminated or drastically reduced the noise for people as well.

May be worth trying.

 

Interesting. Those springs are so damned noisy it's best to keep them soaked with lube. Rust prevention is a good side benefit.

 

Yeah there are posts in this thread about it.

I don't know if they had to disassemble the leaf pack and spray each leaf or if they just sprayed it directly on the installed pack.

 

The leaf pack squeak is entirely separate from the howl. Replacing the leaf pack removed the howl. However, I still have to apply penetrant (or substitute with another lube like fluid film) to get rid of the squeaking after dusty offroad trips

 

Gotcha. Yeah I remember a few people had mentioned that the fluid film also helped with the howl in particular. Again, all hearsay, but who knows...

https://www.tacomaworld.com/threads...-rear-of-vehicle.532809/page-43#post-21815851

 

I must have lucked out, my springs do not squeak one bit, and they're getting muddy at least once a month.

 

That is my experience. The howl is almost completely gone after fluid film application

 

I fluid filmed for rust protection before the howl started actually. So it didn't help for the howl but happy that it's protected and squeak free (not that it was ever squeaky). I just rinse the bottom every few weeks with clean water no soap. Planning on lift with new leaf pack, wheels and tires in 2020 so we'll see what happens then.

 

LOL...... gotta love it

 

I'll be following along with anyone who gets a lift, tires, and/or gears to see if anything solves the noise. In theory any or all of the above should at least change the frequency of vibrations.

I don't want to spend all my time at the service dept with my brand new truck, then go without my truck for days or weeks, only to have them replace the rear axle and the howl come back in a month or two.

About a year ago, only two weeks after buying a brand new F150, I was at the service dept for my door latches freezing. I couldn't even shut the doors once I opened them! They wouldn't latch at all. Had to put a hair dryer right up to the door latches for several minutes each to thaw them. This happened multiple times. Any time it was below freezing temps.

They did eventually fix the issue, but long story short I spent alot of time on this and I ended up going back for a brake system TSB and other complaints.

That was my Ford experience. I don't wanna go thru any of this BS with Toyota. I will tolerate the howl for now since it's not bad with my seats in the normal position. I'll definitely have them document it at my first service visit, though.

 

In Nov, of '18 I bought an '18 SR5 auto 4X4. It now has ~5500 miles on it, so I'm a bit of an outlier here not being an OR, but in the first couple of hundred miles (before I Fluid Film-ed) I noticed a slight whine at around 30 MPH. Before the snow flew, I was able to FF the truck, making sure that I thoroughly soaked the leaf springs, (no, I didn't separate the springs) hoping to avoid the squeaky leaf spring issue that I read about on this forum. I didn't notice the whine after that, but didn't know if it was related to temperature. I haven't heard the whine since.

In an effort to insure (as much as practical) that I don't "contract" the dreaded whine disease, I plan on changing the rear diff fluid. (Yes, I know that it isn't necessary, but I'm going to do it anyway.) After skimming through the article shared by member ryan760 back in post 5440 (tough read) I have come to the conclusion that this issue is far more complicated than I had assumed. With that said, the contact friction between the ring and pinion gears appears to be a "higher order function" in the generation of the NVH. I have used, liked, and will probably end up using the Amsoil Severe Gear, but I'm also looking into the Red Line Shock Proof. I can't find too much information on the Shock Proof lube.

 

Toyota's stance on the issue is that it's normal gear mesh vibrations from the ring and pinion being amplified by the axle housing through the springs, frame, and into the cab via the rear cab mounts. This is the engineering logic laid out in T-SB-0013-18.

Obviously there's a lot of debate on this... many owners are blaming the diffs being made with poor tolerances, but these arguments are not based on anything concrete, just speculation. Some members have claimed to have their diffs examined by independent shops and those shops said there were no issues with preload, shiming, or wear patterns. Others have had their diffs fail for no particular or apparent reason (@The Real Moondog ).

It's a very complicated issue IMO. Personally, I'm inclined to side with Toyota on this as they have likely had engineers take a closer look at the issue to avoid any potential liability should the diffs turn out to be a safety hazard. There's an incentive for them to at least investigate the issue to avoid lawsuits. And they're probably right... it's probably just NVH.

 

This sums it up well. I tend to think the diffs are just noisy. Why? I don’t know. My diff was examined by Toyota and found to have ground gears and the pinion angle was off. I think the tolerances could be off on some (as they could be with any manufacturer) but in the end some set ups just make more noise than others. I have yet to hear of a 3rd gen diff grenading. I can tell you that I have had that happen in an old Chevy and you’ll sure as heck know when the difference between this howl and the howl a diff that is about to grenade makes. No matter what the reason, this is an issue that should be properly fixed by Toyota (so I can get another one). Be well and I’m back to work....

 

I hope this works but I think so far we are batting 0 on the diff replacement working. @nDub and I are living proof.....

 

I think we would all be curious to see some updates on this after some miles with the new diff.