Not often do I need to take my SC up to 4-5k RPM in low gear, except for overtaking, but recently it starts to judder when I do so.

If I drive 'normally' there's no judder at 4000 RPM, but does so if accelerating hard. Not sure if it's the engine or gearbox, but tempted to go with gearbox. It's as though it's unsure whether to change up a gear or not. If I release the accelerator a touch, then it changes, if i keep accelerating it'll eventually change gear at 4500 RPM. In sports mode this all changes to the 4500 RPM stage.

Recently I've had all lambda sensors changed, low suspension arms and MAF sensor - but can't see how any of these would cause this fault. A few times I've had the 'Engine underperforming' (or similar) message and only once did it go into limp mode. Put this down to lambdas as there was a wire loose and it's not happened since.

Where's the first place I should start looking to try and solve this problem ? Thanks in advance  RR Sport Supercharged Vesuvius Orange 4.2 V8 First edition

Prefer RR Vouge S/C but they don't do Orange !

Ah ! Sorry,wrong category,as I don't have the 'fix'bit - can it be moved tocorrect section please?  RR Sport Supercharged Vesuvius Orange 4.2 V8 First edition

Prefer RR Vouge S/C but they don't do Orange !

If you're confident its not a miss-fire I'd check the propshaft and its joints.

I would suggest it is worth getting your transmission flushed and an adaptive reset done by someone with a Faultmate Paul Redding
+44 (0)23 8052 2776
paul@advancedfactors.co.uk

anyone here do the reset ? I'm in Manchester for a week  RR Sport Supercharged Vesuvius Orange 4.2 V8 First edition

Prefer RR Vouge S/C but they don't do Orange !

Flack - Preston
Bodsy - Shropshire

Both have the kit - pick your closest and see if they can help with the diagnosis Paul Redding
+44 (0)23 8052 2776
paul@advancedfactors.co.uk