Help ID this driveline noise- unbalanced propshaft or something else?

[Toxic_Avenger]

LHS Rear noise at low load_coast.mp3

Attached is a phone recording of a driveline noise I have. have a listen and let's play 'Identify that Defender Noise!'

It is a knocking / rattling noise that is present under the following conditions:
-Noise is more prevalent at higher speeds (noise and frequency)
-Present at Constant speed, low load, ie constant speed cruise conditions on a flat road
-Present when Coasting in neutral (this is when it is most easily replicated)
-Cannot be replicated revving engine while stationary in Neutral (so not an engine rotating mass issue, thankfully)
-Appears to be coming from LHS rear (passenger rear) of vehicle.

I did recently take the prop shafts off to re-grease them and check condition, the rear shaft slip joint was disassembled carelessly by me, and put back together at 45 degree phasing per FSM- it may be possible I'm 180 degrees out of phase. If anyone can confirm that this is a unbalanced shaft noise, that might narrow it down somewhat (although pumpkin and prop shaft is located on RHS rear, away from the perceived noise source). Otherwise, needle bearings were in good service on all prop shafts.
Shafts were assembled with slip-yoke end towards the differentials.

All bushes are serviceable but worn.
Going around under car tapping things with a rubber mallet cannot replicate the noise.
Brake shield and shock absorber are not broken.

Sound like an unbalanced driveshaft, or should I be looking elsewhere?

[Toxic_Avenger]

Changed the phasing on the rear prop shaft slip yoke 180 degrees, which retained the 45 degree phasing that LR service manual recommends. No change.

[Disco-tastic]

I had something that follows your description on my D1 after installing a 2nd hand rear drive shaft. It was terrible at 80kph but would disappear on power or engine braking.

Turned out the shaft splines were buggered. Replaced it with a better one and problem went away.

It sounds like you've just gone over yours for a service so not sure why they would suddenly be playing up. Could it be transfer case slop? Or the rear diff?

[JDNSW]

Sounds to me as if something is actually loose! But while it is clearly related to whether it is driving or not, I would (after checking nothing is loose on the tailshaft you have been working on) look for a piece of bodywork that is touching the engine or drive train or exhaust system as the engine/gearbox moves on its mounts with the torque applied.

[karlz]

Possibly a tyre.

I had a noise that would appear at around 60kph.
I thought my diff was stuffed, so took it to the dealer and they said nah, its a tyre.
So then I had the tyres balanced and rotated, noise disappeared at 60kph, but re-appeared at 80kph.

Sometime later, I bought new tyres and the noise was gone.

[Toxic_Avenger]

Part of the exhaust work I have recently done involved removal of both shafts, and piping is clear of all rotating parts. I've gone over all parts to check for loose or missing components, likewise all bolts of the propshaft are tight.

Looking at the service manual again, It appears I've got the slip yokes (for front and rear shafts) facing the diffs, not the transfer case. Not sure if this is a likely cause (shouldn't affect balance though)

Tyre is interesting, but not sure how a tyre defect would be present depending on engine load?

[karlz]

Reread post.
Still reckon its a tyre.

[Toxic_Avenger]

For those interested, it was likely the rear diff centre.
I was 4-wheeling and the rear diff has let go (crown wheel or pinion gear- post-mortem pending). This has also taken the front diff centre (or CV) with it when the whole driveline got shock loaded on a steep rocky climb.
I'll do a write up of my findings when I can.

[Lionelgee]

For those interested, it was likely the rear diff centre.
I was 4-wheeling and the rear diff has let go (crown wheel or pinion gear- post-mortem pending). This has also taken the front diff centre (or CV) with it when the whole driveline got shock loaded on a steep rocky climb.
I'll do a write up of my findings when I can.

G'day Mitch,

Sorry to hear about your loss of drive line. Sounds like it happened in a potentially precarious situation. Plus, a potentially expensive fix too.

Did you have any dramas getting yourself and the vehicle back home? Was it one of those "we will not go off the bitumen" type of tow companies or automotive club coverage situations?

All the best with the repairs.

Kind regards
Lionel

[cuppabillytea]

Hi Mitch. I was going to suggest, without doing any research, that it might be a worn or missing spacer associated with a thrust bearing, which would intern suggest somewhere in the differential. Postmortem will probably give the answer, but I'd bet the noise will be gone after rebuild.