Transmission or transfer case?

[Mafiand]

After traipsing through many threads on transmission and/or transfer case issues I couldn't find something that fully matched up with my issues so I thought I would start a new thread. I have the E53 diesel with ZF 6 speed.

My issue: Under medium to hard acceleration (through the lower gears especially) there is a slipping feeling as well as a mild shudder, first gear is the worst, it doesn't really change with the increase of rpm and feels more like a 'load based thing'. This is sometimes accompanied by a rougher than normal gear change between first and second but not as bad after this. On low throttle openings everything feels normal. Under higher loads at normal cruising speeds (climbing steep hill/bridge) whilst the revs don't move much more than normal/expected (no real slipping feeling) you can sometimes feel a slight shudder ie drive is not as 'smooth' as normal. The difference doesn't really change much between cold or warm. Sometimes when going up our steep driveway you can feel a slip before it 'takes up' as normal. This is rare though and the torque converter still 'takes up' as it should at 1,200 rpm. There are no obvious, abnormal noises, other than the ones in associated with the shudder.

Background: Car has done 138,000km. Mechatronics replaced 40,000km ago (it went into limp home). When this issue first started happening I had the transmission serviced (with oil change) and the adaptation program reset. No fault codes have come up at any stage. Transmission specialist (they do a lot of ZFs) couldn't really see anything obviously wrong inside when looking and said the fluid whilst a little darker than normal was well within specification/expectation. This service didn't really change things much.

Basically I thought I would put it out to the community if anyone else has experienced something similar and what was done to repair it. I am just looking at possible ideas before taking it to a service department/specialist for further fault finding and spending any more than I have to trying to fix it!

Any assistance is appreciated. Sorry for the 'war and piece' novel!

[kkx5]

Torque converter.

[X5Sport]

And kkx5 will know as it’s his living.

[Mafiand]

Thanks KKX5, my original thought was the Torque Converter too, however the transmission repair shop, who do a lot of work on the ZFs, couldn't find any real problems with it. It worked perfectly fine sitting around 1200rpm on a very steep hill under load. In that situation, there was no shuddering etc and worked like it should. The problem only really surfaced on the open road under medium to WOT.

For S&Gs I started on the simple and changed the transfer case oil. When I dropped the oil it was quite dark, almost black (new oil more like honey) and had a slightly burnt smell (new oil was sweet). Once it was filled with new oil I got the laptop out and reset the VTG adaptations on DIS then went for a test drive. To say there was a difference is an understatement! During the first 'power' run it had a very slight shudder in first but considerably better than it has been for a long time. By the time I got to number 4-5 'power' run (time for the oil to circulate etc) the original problem was pretty much gone and it was back to normal. Each run it was getting better and better even though I don't really understand why this could be the cause on the x-drive models. Everything to me pointed to the torque converter.

Hopefully that was the cause of the problem!

[Alan Gunn]

I had the same problem on my 320d.
I put this in the box and it went ok so confirmed it was the lockup clutches in the torque converter.
Well wort the money to confirm and it could last for some time as well.
https://www.ebay.co.uk/itm/2-TWO-Tubes- ... 1438.l2649

[Bradders]

I had this on my 3.0d X3, exactly the same symptoms, changed the fluid and well, what a massive improvement and like you, I can't quite work out why and can only put it down to the properties in the fluid breaking down.