Thread: Discovery 4 Transfer Case Slop / Thud on Engagement

File attached.

ATF is definitely the wrong fluid.

I would recommend changing to the correct fluid, or try Ravenol DTF-1 as this is known to solve TC issues in BMW and Porsche transfer cases.

A calibration of the Transfer Case Control Module may help as it resets the control module to the current clutch pack dimensions. Normally only needed if components have been changed, or the calibration settings have been lost.

Driveline thud. It’s a disco thing as they age. No one can definitively tell me what causes it. I have it too, and generally find I can drive around it, but for me it’s worst when coasting down a slope, then apply acceleration. This seems to be a case of engine braking then onto power leading to a big negative then positive transition with the largest thump. I’d pay almost anything to solve it.

Just to clarify, the Trans was rebuilt. I only had them replace a seal on the TC that had a very slight weep, as it was would be off to get teams off anyway
To replace the seal they would have had to drop oil and split, thus new fluid after for that as well as the rebuilt trans.

I have an IID and did calibrate myself a while back as I read that cures some issue. I will replace the oil ( can get RP synchromax handily which seems to meet spec.and used by many).

Thanks DiscoJeffster it's a relief to know it's not uncommon and I don't need to panic about it. Its a pity though as the comfort and drivability is a big part of what sets these cars apart and this takes away a little from that.


I've also read on this forum that spline regreasing may solve, based on a slight whistle I think I am developing, I think I am up for Manifold leak Cross over leak, so will get them to check spline for play and regrease also

I also read on Disco3 UK forum someone replaced pretty much their whole drive line before it got solved with front prop shaft replacement which had only very minor play.

While I think I have the slightest of play in the front prop shaft in my case I can now reproduce clunk in TC case with the shifting back and forth between Drive and Reverse on brakes,

Past experience shows it’s not the transfer case sadly. Check this thread from a few years back

High KMS - Transfer case...

It would be logical the internal chain in the TC would stretch and introduce a slop.

Originally Posted by PerthDisco

It would be logical the internal chain in the TC would stretch and introduce a slop.

Transfer Case chain replacement due to stretch (or technically wear) is a pretty common repair needed on many other brands which use the same style of box, but not something you see regularly with the D3/D4.

Eventually the chain will stretch to the point that they will even skip teeth, but yet to see any reports of this being common with the D3/D4, even for high mileage units.

The D3/D4 must have some sort of special oil in it…