Discovery TD5 2004 clutch slip

Hi, I’m wandering if anyone can help me! 2004 disco td5 landmark edition. My clutch has started to slip when it’s under load. I removed the gearbox, to find the clutch plate having no obvious signs of wear..I replaced the duel mass flywheel, new clutch kit including release bearing, and a new genuine spigot bearing.
Put the gearbox back taken it for a drive and it’s exactly the same! The fuel pressure regulator isn’t leaking, neither is the rear main oil seal. There was no contamination on the old clutch plate either. My next step is to replace the slave cylinder to see if it’s not allowing it to return properly, does anyone have any other ideas?

Many thanks David

dbentley said:

My clutch has started to slip when it’s under load.

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Describe exactly what's going on... maybe you just think it's clutch slip while it's something else. Select 3'rd and try to move away with 1500rpm, if you can't or it starts kangarooing the clutch is OK

Hose to slave cylinder collapsed internally acting like a one way valve allowing pressurised fluid through but not back? Never seen it on a clutch but I have on rear brakes so a possibility?

There's no hose to the slave cylinder only solid pipes

Part no. STG101032

https://www.island-4x4.co.uk/clutch-pipe-genuine-stg101032-p-34120.html

Yes, i fitted one of those to mine, that black part is a strong plastic pipe not rubber like other hoses, that material can't collapse inside IMO, from the WSM:
"The master and slave cylinders are connected to each other hydraulically by plastic and metal pipes. The plastic section of the pipe allows ease of pipe routing and also absorbs engine movements and vibrations"