Anyone familiar with the ZF 6HP26 or 28?

[festy]

My parent's Land Rover D4 has recently developed a fault whereby once it's up to temp it fails to engage a clutch for 5th gear when dropping back from 6th under load. The fault being logged is insufficient oil volume for the clutch (yes, the oil level is fine and was recently changed too). When it happens, it either freewheels or drops back into 6th and goes into limp mode.
The box is a ZF 6HP28, which is a lower RPM/higher torque version of the 6HP26.
He contacted ZF and they recommended to leave it for a month in case it just needs to re-learn adaptations, but going through the learn procedure half a dozen times has made no difference.
He's been getting different advice from a variety of sources, ranging from possible worn stator bushes to try replacing the all the solenoids, to a $6k+ rebuild, to "150k, it'll be all worn out"

So a bit of a long shot, but has anyone worked on one of these boxes before?

[HQ355]

Was it doing it before the oil was changed ?

[ejukated]

I think that's the same box as the Fords, maybe there is more info when searching for the same fault relating to a Ford ZF

[Jayme]

Dad had similar issues in his territory zf 6 speed. Turns out he had changed the oil but topped it up without the engine running so it was a few liters short.

[vlad01]

I seen many times the case where auto will die after doing a fluid change if the previous fluid was not done in ages or still the original from factory.

The theory is that as the auto wears and builds excessive wear metals, in turn wears the seals but also the very same particles help keep them from leaking. Change the fluid and it leaks to the point of pressure loss.

Not sure how true it is but I seen many 200k + auto working perfect with factory fluid and then get the first change and dies immediately.

[festy]

The oil was changed a few weeks ago, but hadn't been on any long runs since then so it's probably not a coincidence.
He seems to think it's probably a bit of garbage in a solenoid, related to the oil change - and thinks he knows which solenoid it is too as there's only one unique to the 5/6 change and all other gears work fine.
He's leaning towards replacing them as a set - not a cheap exercise to try on a hunch, but gotta start somewhere...

[Jayme]

arent those boxes very very picky about the oil you use? did you use the genuine ZF oil or some 3rd party oil claiming compatibility? dad shelled out $700 on 20 Liters of the ZF oil

[Holden202T]

that's just another of the many reasons not to own a ford territory

[VL400]

Yes they are really picky on the oil type, and to flush them properly costs a packet due to the amount of oil required - you end up wasting a heap to ensure its all fresh oil in the box. Would do as Jayme suggested and confirm what was used and how it was changed.

[ejukated]

that's just another of the many reasons not to own a ford territory

I must admit I have a 2013 petrol territory and its a great car.... I still love my VS though