So my ZF6HP26 is on the way out at 152,000km, which apparently is par for the course for this fine piece of German engineering. Works well on short journeys, but get it nice and warm and it fails shifting ( I think ) 3 to 4 and invokes the limp mode.
The failure according to most Google hits is due to a worn bush, or maybe more than one, lowering oil pressure and preventing proper clamping of clutch plates etc at around 150,000km.
It could be just a solenoid, but the jury says not very likely.
Getting it fixed at a shop is A$5,000 plus, a bit steep for a car worth at best A$10,000.
Pity about that since the car is generally in good shape for its age and could easily last me another 10 years, so I am juggling the equation of fixing or selling for very little with a suspect transmission.
I have a 2 post hoist in my garage and lots of tools so taking the transmission out is not so bad.
Once out I can strip it, lots of info on Youtube and various sites. Rebuild it with US$500 to US$1,000 of parts depending on what is wrong.
The Australian built Ford falcon used the same ZF box and I have seen non core rebuilds for a reasonable A$2,800. I think that might work if it has the same input and output shafts/flanges.
It may need a swap of the XJ valve body and computer but they are probably O.K. anyway.
I have looked at the X350 Repair Operation manual and it mentions this, with a drawing:
10 Install the rubber blocks supplied with special tool HTJ1200-2, between the front subframe
and the oil pan.
11 . Lower the rear of the transmission.
Not sure what the rubber blocks do, anybody know ?
Also what supports the rear of the engine when the box is removed ?
I am thinking of my V12 XJ-Ss where you need hold up the rear of the engine.