Hum in 5th gear only

Hey folks,

I know there has been some discussions in the past on the 5th gear hum pulsating drone from 45-65 mph. Is this a normal thing? Truck is a 2018 tundra trd sport with 61k miles. Grandpa driven with regular maintenance etc. I just need to know if I have to spend some money getting this thing diagnosed.

recent work: Toyota dealership replaced tranny fluid and I put new tires on. Wildpeak aT4ws.

no vibrations, just the weird pulse sound.

 

I am currently having the same issue with my 2019 Tundra. Have you figured out what was causing the problem?

 

Welcome from OKC! 45 mph in 5th? Why? These trucks can be limited by downshifting out of D and selecting the appropriate highest gear for the terrain. In the city, I usually roll iaround with it limited to 4th unless expressway cruising around 65+. Never see 6th unless out on the highway pouring on the coal.

 

This is a great threat as I'm having this "whaa, whaa, whaa, whaa," droning sound at lower speeds and then seems to go away at higher speeds. I though maybe it was that needle bearing in the front axle that tends to go bad, but a quick switch into 4wheel high dismissed that issue. Does anyone have any idea on the noise? I've rotated and balanced tires, new suspension, have 123k miles. recently did all dif fluid changes.

 

You sure it's not an exhaust drone?

 

My truck is doing this, did you ever figure it out?

 

Maybe it's just particular noise of differential at that rpm or exhaust harmonics as finally mentioned? Might be the tires too. Mine hump a little at 45-48, im sure if i listened super carefup, they might be making some particular noise. I hear other cars often have this hump-hump-hump noises with their oversize tires.

Also, 5th gear at 45, why not? I often cruise in 6th as soon as she shifts, which is 45 onwards. No need to waste gas. We aren't at a racetrack, she can downshift if necessary.

 

Mine makes a whomping vibration through the entire vehicle. And as soon as it shifts it goes away.

i occasionally have some minor shudder between gears.
Transmission was serviced but it did not resolve it. Truck is a 2019 with 58k miles.

toyota had the truck for about two weeks and acknowledged that it makes the noise but was unable to come to any decisive conclusion.

it makes driving the truck a pretty unpleasant experience.

unfortunately so far this truck has been very unreliable, and a regrettable purchase.

my 4.0 2008 Tacoma lasted 465k before I sold it.
I am meticulous with maintenance coming from an Aircraft mechanic background.

 

I noticed the same thing in 5th gear between about 50 and 60 mph when my truck was bone stock with low miles. I can't say exactly what it was, but it was for sure there. The good thing is, it disappeared at some point, but I've also made a few modifications to the truck. I suspect it was/is an odd harmonic in the drivetrain.

A couple of things you can try just for funsies:

- on a straight road, click it in to 4wd and see if it changes. There's a bushing in the front differential that interfaces with the driver side CV axle; it can have issues and make an odd noise, though it usually happens no matter what gear.

- service the differentials and transfer case with a quality synthetic oil. Since your truck is a 2019, the transfer case takes straight 75w which is a $$$ from the dealer. You can use a 75w equivalent from Redline or Ravenol for 1/4 the cost, or simply use 75w90. Most dealers use 75w90, mine included. I will switch it out for Redline 75w eventually.

- Throw some weight in the bed. Seriously. I know that may not sound like it would affect anything, but the way these vehicles are sprung and damped, they ride better with some weight in the bed. Or with some suspension mods, but adding weight doesn't cost very much. IMO, the captured rubber bushing in rear leaf spring eye, combined with the tuning of the leaf spring pack can cause some shimmy and vibration in the rear end from the busing rapidly twisting and unloading. I have no idea if that's part of the harmonic or simply related to the minor shudder between gears.

- I'd say to grease your u-joints, but I believe that Toyota switched to non-greasable units by 2019. So perhaps simply inspect them. Inspect the carrier bearing as well - that can often be the cause of a shimmy/shudder, especially on vehicles with a mild lift in the rear. On a totally stock, unloaded truck, I suspect it can also have an effect.

- Play with your tire inflation pressure and see if anything changes.

Hopefully you can get if figured out. The other good news is, my '13 has 230k virtually trouble free miles on it. My '21 just rolled past 70k miles and doesn't seem to have the same issue in 5th. The '13 has some mods, the '21 is stock except for new suspension that is close to stock height.

 

Hey guys,

sorry for the late reply. The issue was a rear wheel bearing that was on its way out. The hum from the RR wheel bearing was bouncing off the exhaust harmonics is my best guess.

The bearing failed on me during a trip with the family in August. Once repaired, I have no more hum or pulse and now as quiet the day I drove it off the lot.

Take a temp gun with you after a good drive and see if your hubs have some inconsistent heat temps. That worked for me.

cheers,

Ryan

 

5th and 6th gears have torque converter lockup modes and a strange hybrid mode that pulses the lockup on and off very quickly. It’s possible other drivetrain wear plus this torque converter pulsing on/off creates a harmonic/humming effect.

 

I think you may be correct. I mostly drive in S4 and the overdrive gears do have both a different sound and feel as well. More noticable if you don't use them regularly.