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Pulsating Low Pitch Hum/Drone

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22 Aug 2024 16:05 #257279 by LLsJnA
Please help with mystery pulsating low pitch drone/hum2018 S. Jimny, purchased used in '22, low kilometers, WITH the noise (unfortunately noticed post-purchase). Non-modified, has factory recommend road tires. The sound is especially noticable on smooth roads between 40-70 km/hr but at any speed. It is not very loud and most people assume it is tire noise but it is not an even sound like you would get from tire tread, it is more of a pulsating sound. Going around turns or braking does not seem to make a diifference with the noise, applying clutch and gearing up or down or coasting out of gear (when it's best heard) makes no change in the sound. Important to note that the pulsation increases/decreases with velocity, suggesting rotational... I have installed a new set of tires since the noise started and it made no difference, and rotating tires did not help. The sound seems to come from the drivers side front (when windows up) but reading of this, the noise could be referring from the rear. When windows down, can't be determined (center?) It sounds like it could be a bad wheel bearing but after two years and a LOT of kilometers I would expect a wheel bearing to get louder and that has not happened. The sound has remained the same. I've had mechanics check and all systems  appear sound (brakes, bearings, gear related, etc.)I appreciate any help/suggestions. The noise drives me out of my mind, mostly due to that I don't  know what it is and if it would pose a danger while underway and cause us to drive off of a cliff if whatever it is gives out or leaves us stranded in remote areas (of which we travel through often).

 Important to note (and possibly related but probably a separate issue):when at speeds of 60-70km/hr and brakes are lightly applied, only when down hill (doesn't happen on flat smooth road) there's a slight vibration. Could this be the beginning of the infamous Jimny death wobble?  

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22 Aug 2024 16:17 #257280 by mlines
This sounds like normal transfer box noise to be honest.  If the tyres are at the correct pressure (23/26 PSI) and the bearings are ok all round then it could be standard noise from the transfer chain.

The Jimny has a reputation for warping disks, sounds like you might have a slightly warped disk

Martin

2003 M13 early KAP build.
3" Trailmaster lift with 1.5 Spacers on front
Customised winch bumper and roll cage
235/85R16 Maxxis Bighorns on 16" Rims, 4:1 Rocklobster, Rear ARB locker and on-board air
Corrected arms all-round, rear disks, Recaro seats and harnesses

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22 Aug 2024 17:16 #257281 by LLsJnA
Thank you Martin, this makes me feel a bit better.
The slightly warped disk:
Could you tell me which disk? I'm not a mechanic and would like to ask the mechanic I've been using to check the things suggested to consider here.
We are very rural in location and mechanics are few, and their resources even fewer.
Your help is much appreciated

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22 Aug 2024 17:23 #257282 by yakuza
Could try to change the tire pressure to see if the noise changes to rule out the tires. for a short period there is no harm in trying with a low pressure like 1.5 bar or a higher up to nearer to what the marking on the tire says is max

Norway 2005 Jimny M16A VVT, 235 BFG MT, 2" Trailmaster, ARB rear lck, 17%/87% high/low gears.

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22 Aug 2024 17:43 #257283 by fordem
Do a Google search for "chassis ear" - essentially a set of microphones that can be attached to various parts of the car and you can switch from one to the next to narrow down the origin of the noise.

The original "Steelman" product is quite expensive, but there are reasonably priced chinese models that will do the job.

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24 Aug 2024 14:50 #257321 by jackonlyjack
Change oil in transfer box
And replace the rear engine mount found at the back of the gearbox 

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24 Aug 2024 14:57 #257322 by Rogerzilla
Does it change (or go away) when cornering?

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25 Aug 2024 13:54 #257342 by LLsJnA
Thank you, we are locating high quality gear oil, what is available (I'm told) isn't good quality. I will notify you on the results.

The rear engine mount at the back of the gear box. I will look in to this... would this be (if broken or worn) be causing a sound such as described?

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25 Aug 2024 14:00 #257343 by LLsJnA
No. The sound is very steady, wether upon cornering or taking the car out of gear and coasting, the sounds remains. The "pulsation" decreases with the decrease in velocity.

It's hard to describe; pulsating is the best I can come up with. It would be similar to the sound of a truck tire in balanced perhaps.

The tires on this little car have been replaced, balanced and the alignment numerous times which lends to another possible clue. Regardless of multiple alignments, it wants to pull to the right

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26 Aug 2024 17:23 - 26 Aug 2024 17:28 #257358 by jackonlyjack
I replace the rear engine mount every year
Not to expensive and takes 10 minutes to change 
Will reduce vibration if it's worn or failed 
Your problem could be a worn uj joint on the propshaft

After a short drive place a hand on each front wheel if one side feels hot you have a sticking caliper this could cause pulling to one side 
Last edit: 26 Aug 2024 17:28 by jackonlyjack.

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28 Aug 2024 17:03 #257365 by LLsJnA
This is fantastic información! Thank you.

Once I am able to do your troubleshooting discovery methods and gather parts (I prefer original Suz parts and have to order from agency) and oils, I will let you know how things go!

Any other things you can offer, I'm all near hearing it and sharing with the mecanico. He too is open to suggestions. Your help is much appreciated!

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