53 D5 gearbox slip on long drive, lucas stop slip fluid??

[Phil in england]

Volvo D5 Auto with engine remap - haven't been driving it like and idiot but occasionally get a smile from putting it in D3 and blowing past the traffic.

However in the last couple of years a fault has begun to creep in. At first it only happened in D5 but now it does it in D4 and even slightly in D3. (When I say "D" I mean I manually select the gear with the geartronic shift).

Problem as follows: Put it in say, D4 or D5 after the torque converter lockup clutch is activated and floor the accelerator right away and you get a nasty juddering with the revs going up more than they should. Ease off the accelerator a little and it all settles down. It only happens when the lockup is engaged, never when it isn't.

It seems that the lockup clutch is slipping, it's very similar to when a manual gearbox clutch is slipping/worn and you get that nasty clutch judder.

However, here's the mystery: If you press the accelerator down more slowly, for instance take a couple of seconds to feed the power up to full power, you get no slip at all.

It seems that something in the system is "sluggish" and can't keep up with a quick demand for clutch grip when "flooring it".

Someone tells me it could be a sticky solenoid, someone else tells me it's the valve block, someone else tells me it's the clutch that's worn (but then why does it grip on full power when I press right down more slowly?). Someone tells me it's the gearbox software, I've just had the software updated on the gearbox today but the symptoms persist.

Has anybody out there had experience of these symptoms? My D5 is gettling a bit old with 120k on the clock now, so I'd rather not spend 4-digit numbers on it, I can drive it normally in fully auto but then I miss the fun of quick overtakes when in manual change mode! Any help gratefully appreciated.