Selespeed skipping 4th
I recently (august) bought my 147 selespeed privately and up until now it's been running brilliantly, apart from the occasional light whine in 2nd gear. On Sunday it developed a constant whine in all gears while under load, and it's started to miss 4th gear on the upshift and go straight to 5th, but changing down from 5th to 4th isn't a problem so far. It feels like it attempts 4th, it doesn't work, so it goes for 5th.
I've never had an automatic car before, let alone a selespeed so I have no experience with them. A friend has said auto's can begin to whine a lot when the clutch starts to go, could this be a possible cause?
Thanks in advance for any advice.