Highway drone and loud idle?

Jean Mercier said:

There are 0 countries in the European Union where English is the official language, therefore it is indeed not used

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Is English the official language of the Republic of Ireland?, still in the EU.
Interesting whilst the Republic of Ireland is an EU country, UK residents can still enter it directly from Britain without a passport.

Eric said:

Is English the official language of the Republic of Ireland?, still in the EU.
Interesting whilst the Republic of Ireland is an EU country, UK residents can still enter it directly without a passport.

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Oooh, yes, shit, big mistake, excuse me Ireland

Eric said:

Is English the official language of the Republic of Ireland?, still in the EU.
Interesting whilst the Republic of Ireland is an EU country, UK residents can still enter it directly from Britain without a passport.

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It's called the Common Travel Area, applicable to The Channel Islands and Isle of Man too. 100% freedom of movement, you can even vote if you move to the any other areas.
Correct, no passport requirements (Except Ryan Air) but identity required if you are flying (one of my colleagues used his library card!)

Earthwatcher said:

Running a Grenadier alongside a new Defender, both bought about six months apart (Defender first while the Gren was on order waiting for launch - I got impatient!), I'm amazed that anyone could describe the Defender as the noisier of the two. The new Defender is a fantastic car - smooth to drive and great for the kind of offroading I do, mainly gravelly rutted tracks on fishing beats. The interior arrangement for gear and dogs works so well. I like the Grenadier, it feels as solid as a rock, and the on road drive noise is kind of what I'd expect, but for sure it's noticeably whiny. I didn't buy the Grenadier for sophistication but I didn't bargain for all the software issues and generally poor interior - plastics a bit naff, not great storage in front for sunglasses, phone etc, folding rear seat "ledge". LR sorted all that in the Defender. Yes, the ND is a million miles from the original and a completely different look, unlike the generic Grenadier, moulded in the traditionally rugged values of the Defender. We can argue all day about "better" but for most needs, the Defender is my "go to" vehicle. I've had 22,000 trouble free miles, while I've clocked just over 4,000 in the Gren which has been back to the dealers for software fixes a couple of times plus an eye-wateringly expensive first service.

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Did you shop around for the service?
Usually around the £500 mark which included a diff oil change.

Earthwatcher said:

Running a Grenadier alongside a new Defender, both bought about six months apart (Defender first while the Gren was on order waiting for launch - I got impatient!), I'm amazed that anyone could describe the Defender as the noisier of the two. The new Defender is a fantastic car - smooth to drive and great for the kind of offroading I do, mainly gravelly rutted tracks on fishing beats. The interior arrangement for gear and dogs works so well. I like the Grenadier, it feels as solid as a rock, and the on road drive noise is kind of what I'd expect, but for sure it's noticeably whiny. I didn't buy the Grenadier for sophistication but I didn't bargain for all the software issues and generally poor interior - plastics a bit naff, not great storage in front for sunglasses, phone etc, folding rear seat "ledge". LR sorted all that in the Defender. Yes, the ND is a million miles from the original and a completely different look, unlike the generic Grenadier, moulded in the traditionally rugged values of the Defender. We can argue all day about "better" but for most needs, the Defender is my "go to" vehicle. I've had 22,000 trouble free miles, while I've clocked just over 4,000 in the Gren which has been back to the dealers for software fixes a couple of times plus an eye-wateringly expensive first service.

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Yea, if you took two parties disinterested in cars, had them drive them, and asked which one cost more, none would get it right. Between the two, for me, it came down to the lockers. I cannot fathom why anyone would want this truck without them.

Dave Rosenthal said:

@Quartermaster Thanks for the suggestion on removing the spare. I really thought that would make a big difference, but oddly the spare doesn't seem very involved at all... Alas the vibration seems to be is something far more complex than just the door moving in and out.
@zvakanaka It's totally possible for exhaust harmonics to stimulate a resonance. But, at ~1800 rpm where the drone is stimulated, the engine would be turning at 30Hz, and the 1st harmonic would be 60hz (neither 47 Hz) so I think it's unlikely that what's happening here. (Also changing gear/engine speed doesn't change it.) Driveshafts are why 65 mph is particularly noticeable.
@Chadd7 Yes, totally possible the process of repairing the transfer case somehow put the driveshafts and gears in better balance and reduced your drone at 65.
@Catpaw4x4 Profession: software, with a side of robotics. Acoustics is a hobby.
@Mike Morrison If spray foam was reversible I would have already tried it It might come to that...
@Skydance I have sound deadening sheets on order. But I'm not optimistic... The frequency is fairly low, and access to the inside of the tailgate is very limited due to the welded-shut construction.
@Karearea Cold temps tends to make compliant materials stiffer, which could help dampen things. Interesting observation...

Also, just so that everyone can hear what we are talking about, attached is an audio clip of my grenadier going down a road at only 25mph, and another at 65mph. Frequency analysis shows a strong peak at 46Hz in both situations, and you can hear that very low resonance (like a subwoofer) constantly. You will have to put on headphones to hear it; your phone or desktop speakers will not reproduce that low.

I did a fair bit of work tonight on trying to tame the resonance, but with limited success (best result so far was impractically wedging something between the spare tire and outside rear glass to dampen the glass, which was a measurable, but not massive improvement) So, nothing I can recommend yet. Oh, and I further strengthened the case for the role of the tailgate by running my controlled test loop and confirming the resonance was gone with the tailgates open.

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It’s fantastic research you’ve actually done.

I have a feeling that the resonance is affecting most Grenadiers in different ways. Root cause my dealer said is from the heavy duty engine mounts and the engine.

My resonance is metallic, underload, going up hill, certain rev range. Spent 1 year bending heat shields and it’s 95% gone. I can only hear it if I go looking for it or under heavy load but I can feel the vibrations, it’s not silky smooth.

Dave Rosenthal said:

@Quartermaster Thanks for the suggestion on removing the spare. I really thought that would make a big difference, but oddly the spare doesn't seem very involved at all... Alas the vibration seems to be is something far more complex than just the door moving in and out.
@zvakanaka It's totally possible for exhaust harmonics to stimulate a resonance. But, at ~1800 rpm where the drone is stimulated, the engine would be turning at 30Hz, and the 1st harmonic would be 60hz (neither 47 Hz) so I think it's unlikely that what's happening here. (Also changing gear/engine speed doesn't change it.) Driveshafts are why 65 mph is particularly noticeable.
@Chadd7 Yes, totally possible the process of repairing the transfer case somehow put the driveshafts and gears in better balance and reduced your drone at 65.
@Catpaw4x4 Profession: software, with a side of robotics. Acoustics is a hobby.
@Mike Morrison If spray foam was reversible I would have already tried it It might come to that...
@Skydance I have sound deadening sheets on order. But I'm not optimistic... The frequency is fairly low, and access to the inside of the tailgate is very limited due to the welded-shut construction.
@Karearea Cold temps tends to make compliant materials stiffer, which could help dampen things. Interesting observation...

Also, just so that everyone can hear what we are talking about, attached is an audio clip of my grenadier going down a road at only 25mph, and another at 65mph. Frequency analysis shows a strong peak at 46Hz in both situations, and you can hear that very low resonance (like a subwoofer) constantly. You will have to put on headphones to hear it; your phone or desktop speakers will not reproduce that low.

I did a fair bit of work tonight on trying to tame the resonance, but with limited success (best result so far was impractically wedging something between the spare tire and outside rear glass to dampen the glass, which was a measurable, but not massive improvement) So, nothing I can recommend yet. Oh, and I further strengthened the case for the role of the tailgate by running my controlled test loop and confirming the resonance was gone with the tailgates open.

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Incredible hobby/passion!
Question - some have bent heat shields and for them that has reduced the noise / harmonics which I am thinking is due to an airflow change as subtle as it is. So would adding underbody protection plates help further? worsen?
Look forward to hearing your thoughts and others (those that have added the protection plates esp!)!
Cheers!

Skydance said:

My resonance is metallic, underload, going up hill, certain rev range. Spent 1 year bending heat shields and it’s 95% gone. I can only hear it if I go looking for it or under heavy load but I can feel the vibrations, it’s not silky smooth.

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Yeah, that’s why I uploaded the sound files to clairify what I meant by “drone” and what other people are experiencing at ~65 mph. It sounds like you were experiencing something different—the 47hz drone is not “metallic” at all. I did play with the heat shields myself and found a couple of places where they were nearly touching and not pushed up all the way to connect securely to the frame. Mine didn’t make a noise, but I see how they could!

We had an old model Defender, bought new in 2006. lt had a bad low frequency vibration at around 65mph which made your ears go funny after a while.

After much investigation it turned out to be an out of balance prop shaft between the transmission and rear axle.

Dave Rosenthal said:

@Quartermaster Thanks for the suggestion on removing the spare. I really thought that would make a big difference, but oddly the spare doesn't seem very involved at all... Alas the vibration seems to be is something far more complex than just the door moving in and out.
@zvakanaka It's totally possible for exhaust harmonics to stimulate a resonance. But, at ~1800 rpm where the drone is stimulated, the engine would be turning at 30Hz, and the 1st harmonic would be 60hz (neither 47 Hz) so I think it's unlikely that what's happening here. (Also changing gear/engine speed doesn't change it.) Driveshafts are why 65 mph is particularly noticeable.
@Chadd7 Yes, totally possible the process of repairing the transfer case somehow put the driveshafts and gears in better balance and reduced your drone at 65.
@Catpaw4x4 Profession: software, with a side of robotics. Acoustics is a hobby.
@Mike Morrison If spray foam was reversible I would have already tried it It might come to that...
@Skydance I have sound deadening sheets on order. But I'm not optimistic... The frequency is fairly low, and access to the inside of the tailgate is very limited due to the welded-shut construction.
@Karearea Cold temps tends to make compliant materials stiffer, which could help dampen things. Interesting observation...

Also, just so that everyone can hear what we are talking about, attached is an audio clip of my grenadier going down a road at only 25mph, and another at 65mph. Frequency analysis shows a strong peak at 46Hz in both situations, and you can hear that very low resonance (like a subwoofer) constantly. You will have to put on headphones to hear it; your phone or desktop speakers will not reproduce that low.

I did a fair bit of work tonight on trying to tame the resonance, but with limited success (best result so far was impractically wedging something between the spare tire and outside rear glass to dampen the glass, which was a measurable, but not massive improvement) So, nothing I can recommend yet. Oh, and I further strengthened the case for the role of the tailgate by running my controlled test loop and confirming the resonance was gone with the tailgates open.

Click to expand...

That’s exactly the deep hum I used to get. After a while my ears would almost ache.

lightning said:

We had an old model Defender, bought new in 2006. lt had a bad low frequency vibration at around 65mph which made your ears go funny after a while.

After much investigation it turned out to be an out of balance prop shaft between the transmission and rear axle.

Click to expand...

Had something similar on my 96 Discovery. Just got used to it doing its vibration at 47-51mph - as long as knew what it was, I was much less worried.

Skydance said:

Did you shop around for the service?
Usually around the £500 mark which included a diff oil change.

Click to expand...

I'd have to go quite a way to shop around but yes, I'll probably do that next time.

Zimm said:

Yea, if you took two parties disinterested in cars, had them drive them, and asked which one cost more, none would get it right. Between the two, for me, it came down to the lockers. I cannot fathom why anyone would want this truck without them.

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The only reason I'd have ordered front and rear lockers would be for the resale where the potential buyer says "I cannot fathom why you'd want this truck without them." The reality for me personally is that I'm never going to need anything other than the centre diff and that would only be on rare occasions. I find the lockers a pain to engage. If I was going to do hard core offroading I'd buy a second hand Discovery 4 or maybe even a late model old Defender which I wouldn't mind getting beat up. The truth is I don't need a Grenadier. I like it for all its faults, but I don't need it. And yes, that resale could be tricky with only the centre diff. It'd be a concern if I was planning to get rid anytime soon. But I ain't.

Earthwatcher said:

The only reason I'd have ordered front and rear lockers would be for the resale where the potential buyer says "I cannot fathom why you'd want this truck without them." The reality for me personally is that I'm never going to need anything other than the centre diff and that would only be on rare occasions. I find the lockers a pain to engage. If I was going to do hard core offroading I'd buy a second hand Discovery 4 or maybe even a late model old Defender which I wouldn't mind getting beat up. The truth is I don't need a Grenadier. I like it for all its faults, but I don't need it. And yes, that resale could be tricky with only the centre diff. It'd be a concern if I was planning to get rid anytime soon. But I ain't.

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Due to the general impracticality of the truck as a mere dirtroader when compared to the general more luxurious, better riding, more efficient dirtroader crowd, resale most definitely falls under the "unfathomable" moniker. During the preorder phase, when someone asked if they should get the lockers if just ordering the base trim, the answer was 'yes' since it doesn't appear likely any aftermarket options will materialize.

I have a 1000 miles on mine in mixed driving bringing it home from Portland and some additional break in and it sounds like normal "truck noises" to me.

OK, I'm back to report on progress engineering a solution for this darn drone. It's been very tricky. I haven't figured it all the way out yet, but I'm making progress. The first thing I worked to do was to fix the resonating glass. If you recall, the glass resonated strongly:



This resonance at ~60Hz was close enough to the door resonance at ~48Hz that the window was amplifying the issue. I tried putting EPDM gaskets around the glass touching the plastic trim, but it didn't do much. On to something more dramatic: I adhered a 1" aluminum section vertically to the glass. This both dampens the glass, but, more importantly, increases the resonance frequency to well above the door itself. Here's what that looks like:
View attachment IMG_1125.jpeg

And here is the resonance of the glass now:



Quite a difference. Note that the absolute scale (brightness) is not calibrated here, but the strength is way lower and the (minimal) resonance is now up at 80 hz. So, did it do anything the overall drone? Well, I don't have the best testing lab, but with alternating tests my guess is that it helped the overall drone about 2dB. Is that a lot? Not really. It's like turning the volume down one or two clicks. More work to go...

[Insert hours of trying stuff that doesn't do much]. Then, after two days of testing and very little progress I had a miracle run, where the resonance was almost completely gone (down 10dB!) I of course attributed it to the last thing I had changed (lowering the pressure of the spare tire) and wondered how that had helped so much. My joy was short lived when I did another test and the drone came right back. What?!

Racking my brain, I remembered that the door might have shut a little funny for one of the tests. I decided to investigate. It turns out the the lower latch on the larger door has three positions it can "click" into and still report to the truck that it is shut. After more experimentation, I was able to reproduce the miracle. If I am very gentle (push the big tailgate shut, hear the click on the top latch, hear the first click on the bottom latch, but no more, then shut the small tailgate hard) I can get my Grenadier into it's magical state. In this state there is only a "weak shut" on the bottom of the tailgate, but it is actually latched... Also in this state, the vehicle's drone is essentially completely gone! (Presumably due to the looser coupling of the tailgate to the latch). Here are the graphics:

Baseline, with the door shut normally:


And "magical" with the door shut to one click on the large bottom latch:


You can visually see how much less intense this is. Detailed spectrum analysis is even more dramatic, and shows a 8+ dB reduction in the resonance peak (like 5 clicks of volume)! This a massive improvement and essentially completely fixes the issue.

So, I now have a way to reliably shut the tailgate that fixes my drone issue. Will this work for you? Maybe, but this also might partially explain why some people seem to have this worse than others--it's dependent of the exact fit of the latches and how hard you slam your doors! Speculating, the exact amount that the U bars protrude from the vehicle might affect this a lot. If they are aligned perfectly top to bottom the tailgate might be in a nice state of floating (which the latches are designed to allow). If the top and bottom are misaligned, it might preload the latches, undermining their floating design and tuning it into a braced drum.

I'm going to keep the work going. I have a tailgate table coming, and I'm going to experiment with that, and also use it as a mechanism of apply a considerable amount of constrained later damping (CLD) to the tailgate area. I don't expect much, but it's worth the testing. (Quick update: GP Factor tailgate table arrived tonight and I bolted it on. It might have helped a tiny bit--within my margin of error. It stiffened the door a bit and shifted the resonance up 3Hz--not a bit deal.)

I'll be out for a week on a trip so no more progress imminent, but I figured you folks would want the update.

Wow! Awesome work man
I will experiment with the subtle large door closing technique too
Kinda funny as my back doors have an occasional rattle/knock when crossing rough areas on gravel roads, which I am intending to investigate when back home!
Thanks for all the efforts

Dave Rosenthal said:

OK, I'm back to report on progress engineering a solution for this darn drone. It's been very tricky. I haven't figured it all the way out yet, but I'm making progress. The first thing I worked to do was to fix the resonating glass. If you recall, the glass resonated strongly:

View attachment 7869510

This resonance at ~60Hz was close enough to the door resonance at ~48Hz that the window was amplifying the issue. I tried putting EPDM gaskets around the glass touching the plastic trim, but it didn't do much. On to something more dramatic: I adhered a 1" aluminum section vertically to the glass. This both dampens the glass, but, more importantly, increases the resonance frequency to well above the door itself. Here's what that looks like:
View attachment 7869513

And here is the resonance of the glass now:

View attachment 7869514

Quite a difference. Note that the absolute scale (brightness) is not calibrated here, but the strength is way lower and the (minimal) resonance is now up at 80 hz. So, did it do anything the overall drone? Well, I don't have the best testing lab, but with alternating tests my guess is that it helped the overall drone about 2dB. Is that a lot? Not really. It's like turning the volume down one or two clicks. More work to go...

[Insert hours of trying stuff that doesn't do much]. Then, after two days of testing and very little progress I had a miracle run, where the resonance was almost completely gone (down 10dB!) I of course attributed it to the last thing I had changed (lowering the pressure of the spare tire) and wondered how that had helped so much. My joy was short lived when I did another test and the drone came right back. What?!

Racking my brain, I remembered that the door might have shut a little funny for one of the tests. I decided to investigate. It turns out the the lower latch on the larger door has three positions it can "click" into and still report to the truck that it is shut. After more experimentation, I was able to reproduce the miracle. If I am very gentle (push the big tailgate shut, hear the click on the top latch, hear the first click on the bottom latch, but no more, then shut the small tailgate hard) I can get my Grenadier into it's magical state. In this state there is only a "weak shut" on the bottom of the tailgate, but it is actually latched... Also in this state, the vehicle's drone is essentially completely gone! (Presumably due to the looser coupling of the tailgate to the latch). Here are the graphics:

Baseline, with the door shut normally:
View attachment 7869516

And "magical" with the door shut to one click on the large bottom latch:
View attachment 7869519

You can visually see how much less intense this is. Detailed spectrum analysis is even more dramatic, and shows a 8+ dB reduction in the resonance peak (like 5 clicks of volume)! This a massive improvement and essentially completely fixes the issue.

So, I now have a way to reliably shut the tailgate that fixes my drone issue. Will this work for you? Maybe, but this also might partially explain why some people seem to have this worse than others--it's dependent of the exact fit of the latches and how hard you slam your doors! Speculating, the exact amount that the U bars protrude from the vehicle might affect this a lot. If they are aligned perfectly top to bottom the tailgate might be in a nice state of floating (which the latches are designed to allow). If the top and bottom are misaligned, it might preload the latches, undermining their floating design and tuning it into a braced drum.

I'm going to keep the work going. I have a tailgate table coming, and I'm going to experiment with that, and also use it as a mechanism of apply a considerable amount of constrained later damping (CLD) to the tailgate area. I don't expect much, but it's worth the testing. (Quick update: GP Factor tailgate table arrived tonight and I bolted it on. It might have helped a tiny bit--within my margin of error. It stiffened the door a bit and shifted the resonance up 3Hz--not a bit deal.)

I'll be out for a week on a trip so no more progress imminent, but I figured you folks would want the update.

Click to expand...

First: congratulations for your acoustic analysis (I have to say this, as I´m a professor of engeneering in acoustics)! Secound: The advice to have a look on the back-doors closing-behavior is very helpfully. For my car the upper latch was not well alligned so the door was not locked there. This was not signed by the electric door-open-contacts. So I recomend everybody to check this for your car.
Greetings from Germany, Karl

Awesome work

You're doing lneos's R&D for them!

Is it possible it’s not the latch, but the door seal? If it not as tight it can let pressure out eliminating resonance.