Driveline and engine harshness accelerating in 4H

[MarkAW]

Think I have jinxed myself discussing 4H on here.

For the last 3months and 15,000km or so I’ve been towing the caravan in 4H without a drama.

Today I was pulling into Alice Springs on the way back to Melbourne and the front wheel super select lights started flashing whilst in 4H. Switched to 2H no problem and then back into 4H. After a few km they started flashing again then went solid and flashed again.

Back to 2H for 50km or so and back into 4H now without flashing front wheels for the last 30km of the Stuart and around town. Hopefully nothing major was planning on going into Palm Valley in Finke Gorge on the weekend.

Any ideas out there? Cheers

[oscaroo]

I have a 1 week old MY18 Pajero with 2500km

In 4wd it is a bit rougher than 2wd but nothing I would be concerned about.
however, I do feel a *something* under my feet when I start off after having come to a full stop.

The something feels like something disengaging, a bit clunky but also a bit coarse sandpapery.
*shrug

[old Jack]

Thank you all so far. As you can see we’re starting to gather a few accounts of gen 4’s and it’s leaning towards mainly occurring in the later gen 4s.
(My previous vehicle was a petrol ‘06 Kia Sorento that had a full chassis and part-time 4wd selectable 2H to 4H on the fly off road and could not tell the difference).
While I am yet to start the process of eliminating the different 4wd components as suggested by admin these are some questions that I’d like to put to the forum:
1) What’s changed or different between the older gen 4s and the later models?
2) is this something to do with the more powerful engine in the later gen 4s?
3) is this something to do with the different gearbox in the later gen 4s?
4) Due to cost cutting is the flywheel cheaper but not actually up to the job?

Does anyone know of a Pajero guru in the Brisbane area? TIA

Controlling NVH is a huge challenge for all vehicle manufacturers particularly for vehicles that have monocoque body construction rather than a body on chassis. In a vehicle with a full chassis the body/passenger compartment is completely isolated from the engine and driveline by rubber body mounts so with minimal sound deadening compound and insulation it is reasonably easy to achieve low levels of NVH.The body and chassis have considerable flex and this deters harmonic vibrations from being concentrated and amplified.

However a monocoque construction has a much stiffer body and it flexes much less, so it amplifies any noise and vibrations more. The engine and driveline are rubber mounted to subframe chassis that are then bolted on to the monocoque body, the size, shape and hardness of these rubber mounts will determine what frequency harmonics are absorbed by the mount or transmitted through to the body. The Gen 4 Pajero, by design, has always been more susceptible to NVH problems and Mitsubihi have gone to significant efforts to minimise this. There a 4 Dynamic Dampeners fitted, these are heavy steel brackets that are fitted with heavy/dense rubber blocks, there are 3 on the rear diff and another 1 on the gearbox. I do not know if all 4 of these dynamic dampeners have been fitted since day 1, or have they have been progressively added as the engines, transmissions, drivelines and tyre's have been changed over the years, which will also effect the NVH. There will also be a difference in the harmonics generated between driving in 2wd and unlocked 4wheel drive as the diff is having to actually "differentiate" the front driveshafts speeds rather than having a driveshaft free wheeling. Load the vehicle up, change tyre's, change suspension, add a bullbar or roof rack, or even change tyre pressures and the harmonic profile will change.

The NX had a significant change from the NW, it has a taller final drive diff ratio by about 10% and I suspect the AT Pulse Width Modulation control of the Torque Convertor lock/unlock positions or the gear change positions have not changed, Marshall from MM4x4 would be able to confirm this. I am not sure if these changes happened when the NX was first released or after the first year or 2, I think the diff ratio changed from 3.917 to 3.692???.

Another factor is every person is different, we actually sense vibrations differently, some people have a much higher sensitivity so it is plausible that a vibration or harshness you feel, many others my not feel it to the same extent or even at all.

For those that are experiencing NVH issues I suggest this may be reduce by removing 1,2,3 or all 4 Dynamic Dampeners. Do this one at a time, then 2 at a time, then 3 at a time, there will be multiple combinations so record each situation and what if any changes you notice.

I know when testing Lockup and Auto Mate there was a significant change on the NVH on my Challenger and it has a separate body and chassis, it was not noisier or quieter just very different!

Gen 4 Auto owners could see what happens when driving in manual shift mode, if you change down a gear so the engine rpm increases what changes can you feel? Also note what changes there are when the TC is locked and unlocked. A good way to differentiate a noise from a vibration is to wear a pair of earmuffs and see if the feeling changes, by reducing the sensitive of one of your senses will heighten the other senses.

OJ.

[JT8D]

Tks oldjack.
Rather than type it all out again can you please read my reply to Glenno regarding difference between 2H and 4H.
I understand your explanations and have tried removing the only dampener left on my rear diff and it made no difference.
The sensation I get in 4H is as though one or several mounts has lost its isolating properties and has become grounded.
Something comes in to play in 4H so it would make sense if a front diff mount was the culprit.
Tks again.

[old Jack]

Hi JT8D,

I have read your reply on the other thread and find the App tool interesting.
Can you eliminated the driveline by using using App and see what change there is when you place the auto in the neutral position whilst moving?

OJ.

[JT8D]

Hi OJ,
Tks again for yr interest in my problem.
Isolating components is a good way to troubleshoot. Essentially in my case however the NVH in my car literally rears it’s ugly head only when under normal acceleration in 4H. Coasting along in 4H does not exhibit anything like what’s its like under acceleration in 4H but the app would show it on its graph however big or small the amplitude is.
It feels like nothing in the driveline is actually out of balance when coasting in 4H but if I can find a downhill run long enough I’ll follow yr suggestion and see if anything else shows up but it’s sophisticated enough to show up the source of any vibs because you enter all of your driveline details so it knows exactly what it’s testing on your vehicle.
Tks again

[PajeroPaul]

Hi,

I have also a problem with noise / whine occurring under light acceleration when in 4H. Just occurred after a week of 4WD in the Vic high country. Prior to this there was no audible or feel difference between 2H and 4H.

Likewise - MY16 NX GLS (no DPF) with 34k on it, but running noisier D694 LT tyres.

Paul

[old Jack]

Hi OJ,
Tks again for yr interest in my problem.
Isolating components is a good way to troubleshoot. Essentially in my case however the NVH in my car literally rears it’s ugly head only when under normal acceleration in 4H. Coasting along in 4H does not exhibit anything like what’s its like under acceleration in 4H but the app would show it on its graph however big or small the amplitude is.
It feels like nothing in the driveline is actually out of balance when coasting in 4H but if I can find a downhill run long enough I’ll follow yr suggestion and see if anything else shows up but it’s sophisticated enough to show up the source of any vibs because you enter all of your driveline details so it knows exactly what it’s testing on your vehicle.
Tks again

No problem JT8D, I have a suspicion it is related to combination of the auto box changing up a gear too early and the increase in final drive ratio. Another check you could do is when you have the resonance flip the gear lever over to sport and drop down a gear. If the noise disappears or reduces then I can recommend a fix for this.

OJ.

[PajeroPaul]

Took mine to the dealer today. They tested the front diff oil and found metal in the oil. Replacement diff on back order for replacement.

[JT8D]

Wow! That’s no good! I hope that fixes the problem you had.
I’ll keep that in mind for when I take mine to the dealership.
It would be good to know what the findings were after they strip the old front diff down.
Would you be kind enough to describe the issue that led you to take it back to the dealership?
TIA.

[Eski]

Took my new MY2019 NX for a scoot today, first mission in 4H on gravel, yes noticed some increase in vibration and to a lesser extent noise - makes sense in that there are more mechanicals spinning and whirring...
Is it a show stopper - not for me, i wanted a 4x4 for the beach; otherwise i would have bought a camry.

Cheers
Eski