My truck is on its 4TH REAR DIFF

Ding! Ding! Ding! "soft metal gears" that answer could be a winner. But I suspect a misaligned carrier bearing housing machine work.

 

If this was a jeep forum, misaligned carrier housing would of been the first and only reply.

 

All oem differentials "axles" from a auto mfg are mass produced by machines or robots . No human interaction is involved so there's imperfections / flaws during the assembly

A driveline shop that has someone assemble a differential by hand will last much longer and be noise free

 

I had a set of US gears , 3:73 ratio in my Camaro that would howl at 50-70 mph . Replaced them with a higher end set and noise went away . Found out later the US gears were soft metal and found alot of similar complaints online

Carrier bearings would produce a low frequency rumbling sound not a high pitch whine

 

I wish a perfect pattern and perfect setup would produce no noise. I have an excellent pattern, preload at 15 in-lbs, backlash at 0.006 and I still get coast noise between 55-65mph (on Nitro 5.29s). This is right around where I got nose on OEM gears too. Like I said previously, Toyota has determined this noise to be normal but has released a TSB to "dampen it" from entering the cabin for lack of a better term.

 

Here is the TSB. It only applies to 2016-2017 vehicles. I got it done on my 2017 OR, it did help. Not sure if it has been expanded to any other years or not.

 

For what it’s worth, my diff is perfectly quiet. Reading this thread makes me think I’m the only lucky one of the bunch. ;>

 

No, you probably have the same problem but likely already have some version of the TSB parts from the factory in your 2020.

 

Good luck OP

 

Is that what you think? I walk through a large plant every month and shit gets tacked in jigs by humans before it is even moved over for robotic welding.

Yes they sometimes have defects in the scrap bin.

 

I think you are on the way to a solution. Good luck.

 

Technically the differential is just housed inside the carrier.

But in a Toyota axle the entire gear, carrier, differential assembly is a drop out third member. The carrier bearings are affixed in the third member, not the axle housing. The entire 3rd member bolts into the axle housing.

 

Back in the day when i setup a 12 bolt chevy posi differential with 4.56 zoom gears, it would howl pretty good. Asked if this was normal for zoom gears... was told it it is, just the nature of what they are.

 

Isn’t this normal? Mines been doing it for about 4000 miles.

 

I would bet it has something to do with bearing preload and gear backlash as well.

 

Didn't read everything here but at this point I'd think you have a bent or defective axle housing? I'm not %100 sure but I believe dealers just swap the whole third member with rear gear problems (the whole clamshell with the front) which would rule out a bad tech lol.

I'd like to see the carrier/side bearings on these diffs.

 

wait... are you running twin turbos and a 3500 rpm stall converter? If no never mind lol.

 

did U but truck new / used ??

the line mechanic/dealer guy is into the void of just switching out parts

as opposed to having a discerning look & assessing what is wrong

NOT knowing & simply replacing is stepping in the SAME pile

9 out o 10 mechanics dont KNOW How to ' set up ' the many types o differentials

fewer still that are experts

the set up on the pinion .............

the actual axle housing could be tweaked

id take to a Real Axle shop

 

Crazy they are replacing the rear diff.. NVH from the rear diff is normal on these trucks. Well documented

 

A lot of people are quick to jump on the "not setup" thing because gears make noise. The fact is some gears and some gear cuts make more noise than others and some vehicles amplify that noise into the cab rather than attenuate them. At this point we've realized gear whine in these trucks is common and normal and not a sign of a mechanical problem or pending failure. Not to say there aren't other noises that could be problematic, however.

For those that think that gear whine means there is a mechanical problem it's important to understand gears make noise and some of the stronger methods of manufacturing and installing gears creates loud, unavoidable gear whine and many OEM gears are actually weaker designs in the interest of reducing noise. So sometimes gear noise = strength and it's just not so simple to assume noise equals problem unless you consider the noise alone the problem, which is justifiable in this day.

I'd bet the OP is just at a dealer willing to chase their tail on a problem that technically isn't one. Not every person/tech/dealer is clued in to all issues or nuances in the same way.