High kms 3.0 drive train harshness

[Stuart02]

I've been shopping the +200 000kms 3.0 D4s and have noticed varying amounts of vibration at low revs and under load - one even at idle.
Having owned a 2.7 V6 and the TDV8, I've admittedly got high expectations on NVH. Is this a kms or 3.0 SDV6 characteristic?
If it's the kms, are we talking engine mounts? Gear box? Something else?

[josh.huber]

Mine is vibration free at 230k BUT, I have a harsh thud when getting on the throttle hard, I'm 99% sure it's the transfer case and I have bought a new one that I need to pick up and fit soon. Centre bearings got talked about a bit but mine is fine. I put a bar on my mounts and was happy enough. Just lower control arms that have been wearing out on mine. All other diff, transfer and auto mounts seem new

[INter674]

8 speed?

Ours is vibration free but even the 8 speed can get caught out eg when slowing down to a roundabout then hitting the gas it will thump quite hard. So need to be more gentle on the gas then...otherwise it's really smooth and on point with gear selection etc and vibe free.

[Eric SDV6SE]

Not a SDV6 characteristic, more to do with wear in the Driveline, regardless of model or spec. There Should not be significant vibrations through the transmission at idle.

thumps can be transfer case thrust bearings, the rear drive shaft bearings or transmission valve body.

Worst case is a failing torque converter, this is a transmission out job, and usually requires a transmission rebuild anyway.

another poster on here advised after a drive shaft change vibration / harshness was much reduced as the bearings in the drive shaft uni joint were buggered.

Transfer cases are pretty strong, replace the fluid and check if the seals are leaking and replace. Royal purple synchromax is a suitable transfer case oil in my view.

another strong recommendation (imho) is to replace the accumulators in the valve body in the transmission, the originals are rubber and flatten out over time, leading to harsh shifting and thumps under load. There’s a Sonnax transmission kit for the 6 and 8 speeds that provides replacement of all the valve seals, accumulators and clutch cylinder valves (the ones that lock up the clutch packs). Leaks over time in these causes low pressure in these lines, resulting in clutch slip and wear. This also means a full fluid volume replacement. LG6 or 8 or equivalent (can of worms opened...again).

ive done the valve body rebuild and transfer case oil change in mine, no vibration, no more shift harshness and thumps when shifting. Yet to check the driveshaft, as I do sometimes get a bump coming back on the throttle. Mines at 196,000km.

Eric

[Stuart02]

8 speed?

Ours is vibration free but even the 8 speed can get caught out eg when slowing down to a roundabout then hitting the gas it will thump quite hard. So need to be more gentle on the gas then...otherwise it's really smooth and on point with gear selection etc and vibe free.Nah just 6 speeds - mid to high $20s is the other criterium and I've only seen one MY2013 in the last few months...