Low Frequency Pulsing Noise @ 40 MPH - Toyota 4Runner Forum

zonzin · 05-10-2021, 07:41 PM

Recently my 4runner has been making a low frequency pulsing noise peaking at 40 mph. It is very pronounced and clocks at 80 decibels , 20 above normal ambient driving noise. At first I thought it was the dreaded needle bearing issue but this noise does not go away when in 4H. In fact, it continues in all gears, and in neutral as well. It starts at about 25 mph peaks at 40, and fades away at 55. I also thought maybe it was the tires, Ridge Grapplers with 32K on them but I replaced them with Toyo AT3's and the noise continues. There is no associated vibration or anything else, just the loud, pulsing noise. Any suggestions?

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mo_mo · 05-10-2021, 07:46 PM

Quote:

Originally Posted by zonzin

Recently my 4runner has been making a low frequency pulsing noise peaking at 40 mph. It is very pronounced and clocks at 80 decibels , 20 above normal ambient driving noise. At first I thought it was the dreaded needle bearing issue but this noise does not go away when in 4H. In fact, it continues in all gears, and in neutral as well. It starts at about 25 mph peaks at 40, and fades away at 55. I also thought maybe it was the tires, Ridge Grapplers with 32K on them but I replaced them with Toyo AT3's and the noise continues. There is no associated vibration or anything else, just the loud, pulsing noise. Any suggestions?

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Are your windows, including the rear, fully closed?

zonzin · 05-10-2021, 08:12 PM

Quote:

Originally Posted by mo_mo

Are your windows, including the rear, fully closed?

Yes they are.

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Bry n · 05-11-2021, 04:19 AM

Have you ever been abducted by aliens? I’m just trying to think outside the box here

Jivewalker · 05-11-2021, 07:38 AM

Drive shaft spiders lubed? how many miles on the runner? Changed the oil in the diffs? Transfer case? Check your wheel bearings. Alignment? I would think tires, but you say you swapped them.

zonzin · 05-11-2021, 11:08 AM

Quote:

Originally Posted by Jivewalker

Drive shaft spiders lubed? how many miles on the runner? Changed the oil in the diffs? Transfer case? Check your wheel bearings. Alignment? I would think tires, but you say you swapped them.

It has 90,000 on it, mobile one 75/90 front and rear diffs, changed every 20,000 . Drive shafts lubed every 5,000 transfer case changed every 20,000 with royal purple. Alignment done dead on.
Maybe it is the needle bearings and mine just presents it a little different than everybody else's?
Ironically I have a set of East Coast gear front rear diffs on the way (4.56). Maybe that'll take care of the issue.

ahtoxa11 · 05-11-2021, 11:51 AM

Quote:

Originally Posted by zonzin

It has 90,000 on it, mobile one 75/90 front and rear diffs, changed every 20,000 . Drive shafts lubed every 5,000 transfer case changed every 20,000 with royal purple. Alignment done dead on.
Maybe it is the needle bearings and mine just presents it a little different than everybody else's?
Ironically I have a set of East Coast gear front rear diffs on the way (4.56). Maybe that'll take care of the issue.

When my needle bearings were noisy, the symptom was exactly as yours except that it did go away win 4hi. But, the speed, the type of sound -- all that was identical. Of course, ECGS bushing fixed it for good.

zonzin · 06-03-2021, 01:01 PM

Quote:

Originally Posted by ahtoxa11

When my needle bearings were noisy, the symptom was exactly as yours except that it did go away win 4hi. But, the speed, the type of sound -- all that was identical. Of course, ECGS bushing fixed it for good.

Yeah because it does not go away in 4hi on mine I'm looking into wheel bearing failure. Researching now.

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Jivewalker · 06-03-2021, 01:11 PM

Quote:

Originally Posted by zonzin

Yeah because it does not go away in 4hi on mine I'm looking into wheel bearing failure. Researching now.

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Jack your truck up, spin wheel, place hand on spring. If you feel vibration in spring there's a good chance wheel bearing is bad. this isn't a tell all, it could still be bad even if you don't feel vibrations.

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