DMAX shake/wobble/surge under low RPM

[nmac]

Hi,

Long time forum watcher, first time poster so hoping the brains trust can help solve this problem like i have used this forum to do in the past.
I have a late 2012 auto dual cab SX DMAX and recently it has developed what I'll call a slight wobble. Not sure shake is the correct word to use here.
Scenario is as follows,
Under light acceleration at low rpm in the region of 1500rpm at a speed around 50-60kph there is what i shall call a wobble where it feels as if it is struggling to drive. Similar to a manual car in too high a gear at a low rpm starting to kangeroo down the road.
This sensation goes if i either press the accelerator down further to increase revs and in turn speed or if i manually shift it into a lower gear.
9 times out of 10 it happens on the 60kph roads in traffic where i am feathering the accelerator to maintain a constant speed.
My best guess is something to do with fuel or air but wanted get some more opinions before i start pulling the engine apart to find the source.
Thanks in advance!

[mydmax]

G'day nmac
Not sure if I am reading this correctly but if always around the same speed it could be the EGR valve is sticking due to carbon buildup. Not sure why an EGR would always malfunction at the same time/condition though.
I take it the feeling is in felt in the driveline, is that correct?

The other thing which it may be is, the tailshaft where the yoke goes into the back of the transfer case mght not be engaged sufficiently and the yoke is vibrating in a rotary fashion but not spinning on centre. Perhaps get underneath and look at it and gauge if it is mostly in there. Try to make it wobble sideways with hand pressure, ie, side to side or up and down. If there is any significant movement you may require a spacer in the rear universal flange to hold the tailshaft closer in the transfer case. Some vehicles had this problem and they were not engaged enough.

If this is difficult or you are unsure, have a mechanic who understands these things to give an opinion.

Both are driveline felt but vastly different causes.

[nmac]

Hey mydmax,

Thanks for the response, to answer your queries it has happened at different speeds but is most common/noticed at that lower speed but in all cases it is occurring in that low rev range of 1000-1500rpm with the accelerator only lightly pressed.

I first thought it might be blockage due to its age, but only has 87000 on odo and has been regularly serviced. The feeling is like its being restricted of either fuel or air and i only describe it like that having driven a lot of boats both 2/4stroke and had the same sensation when the fuel line is block or pinched allowing just enough fuel through when throttle is wide open but struggles when just above idle motoring along.

Ill jump under this arvo and check the tail shaft out for excessive play, last service it got inspected and regreased so maybe its not back in its right spot but i would think if that was the case it would be happening at all speeds and rev ranges?
I was planning on giving the intake and throttle body a clean with one of those spray cleaners so might pull the egr out for a look and see if its blocked up at all.

Thanks again.

[mydmax]

Niacin
If an engine fuel system will let sufficient fuel through for high speed the there is/ has to be plenty for slow speed running.
Blocked or restricted filter or fuel line would preven high speed running.

The greasing of your tailshaft has nothing to do with it not in place correctly. It is either running in a good position or it isn’t.
Have you had different rear springs fitted, sometimes/often replacement spring stuff up uni drive angle and can alter yoke engagement in rear housing.

[nmac]

Thanks again MyDmax,

So have jumped under and have no excessive play with the tail shaft in all directions. In relation to my earlier comment regarding the tailshaft re grease, i should have been a little more detailed.
On the last service i got my mechanic to pull and inspect the rear diff and re oil it, during which he pulled the rear drive shaft out to check for damage after a recent trip away in which it copped a flogging. Either way im ruling out the driveshaft at this stage.

Yes it has been resprung but i got it adjusted at the same time, as i had the mysterious "clunk" some dmax's had from the yoke engagement when i purchased it. It was either this forum or ozisuzu where the adjustment needed was brought to my attention as the fix for the clunk. Which i saved until it was resprung to save doing it twice.

I also pulled the intake this arvo and its crudded up pretty bad, i have time friday and over the weekend to get in there and clean as much as i can out. Then will do a test drive and see if theres any improvement.

Any other thoughts? Thanks again for your help.

[mydmax]

The only way to inspect the rear differential is to take out the axles and unbolt the whole unit from the axle banjo. Did he actually do that? Replacing the oil is a normal task though.

You mentioned at last service the tailshaft was removed. Have you had the problem since then?
It is possible the tailshaft has been replaced on it's spline with the Universal crosses not in synch, ie, the last two not directly in line.
Another is, the rear flange is not seated properly on the diff flange.
Is the centre bearing bellows in good condition? presuming yours has one.

Are you now operating the vehicle since last trip, now unloaded and the rear is sitting higher?
That can cause the replacement springs, which rarely hold the diff with the correct uni attitude and the rearmost uni/pinion shaft is pointing downhill, instead of pointing upward to look at the transfercase.

[nmac]

The problem was occuring prior to last service, and i have a constant load of around 300kgs at all times with work tools being traded for camping gear when on trips away.
If the tailshaft alignment was the cause of the wobble/shake wouldnt it be happening at all times regardless of rpm/speed? This is the only thing that makes me think it is somewhat fuel delivery related due to occuring only when the accelerator is only partly depressed trying to maintain a constant speed.
The shake/wobble is more in the ute rocking back and forward like it would say if you were kangerooing down the road as a learner.

[scozzman]

Did u get this sorted nmac???

I got same problem.

Thanks

[scozzman]

Did u get this sorted nmac???

I got same problem.

Thanks

[ENC]

Sorry to bring this up, but seem to have a similar problem that I just cant find in our 2016. Has anybody got to the bottom of it.
Cheers Ian