TD5 Auto box 'Thumping'?

Hi all, I'm after some help / advice please.
I've got a 2000 TD5 with an auto box. Most of the time it is fine with smooth gear changes both up and down the range. Every now and then and it's only occasionally it seems to thump and snatch at a gear change, there is a loud thumping noise and the whole car judders like it's been kicked. It feels like the car is snatching at the change if that makes sense? It's been happening for some while but is very very intermittent sometimes we can go out for the day and not have it at all, other times four or five on a similar trip? Any advice or ideas what it may be and how much it may cost to fix would be very much appreciated Thanks.

Sounds like its the auto box solonoid playing up. I had the same on a Shogun. It was a cheap fix 50 euros and took the tech an hour to fix.

Hi sorry I dropped off the radar for a couple of days, thanks for that it doesn't sound too bad then, I'll have to get it in to my local specialist and get a quote, thanks again Rich

I had the same snatch gear changes from my TD5 Auto but only when I had run it for 50 miles. I changed the oil and filter in the box, with a second flush after a week as you can't get all the oil out. It was like I had a different disco smooth changes all the way and nearly 10,000 miles without a hint of the problem.