Torque converter lock up fault ?
 

Since buying my diesel Connie a few years ago I've covered 35,000 miles with a slight issue that's a bit of an annoyance . It was getting on my wick yesterday on a drive back from Dumfries so gave me time to ponder.

When driving in top gear and beginning to increase load to climb a slight incline, as my speed increases to between 50 to 55 mph I get a judder from the drive line as if I have a worn ball joint but having checked these and the car has passed all it's MOT's with this fault, I'm wondering if I have a torque converter lock up fault. If I press the accelerator whilst this judder is taking place and get the car to drop to 4th gear , the judder stops and as the speed increases above this speed and the gearbox changes back to top gear and no further judder below or above this speed and otherwise the gearbox is smooth and a joy to use. It just feels as if you are on a rough road surface when this occurs ! :shrug:

I have exactly the same problem, I did think it may be injectors as I changed all four for known good ones, still the same. The car did have a Ron box on it when I bought it, which I took off and put a new maf in it. Perhaps high pressure pump possibility starting to fail because of the box. It's not really a problem but does cause annoyance.

It could well be from the gearbox.
The torque converter lock up works in Drive. It is like a couple of hundred revs increase when you put your foot down a bit, or hit a hill, as the car goes out of lock and into normal converter mode. If that is not enough, it will change into 4th.
If you drive in Sport mode, it will never switch the lock up in, and you will not get that rev increase from the torque converter.
So doing the judder in Drive and trying to do the same in Sport, and you will see if it is the gear change itself or maybe the lock up.
Apart from that, I can only advice you to do an oil change on your box. It might cure it, it might not, but it is relatively cheap and most likely needed.

I have been thinking a gearbox oil change would be a start as I have no record of it being changed. I’ll test it in sport at the weekend under the slight load as it is only occurring in 5th in drive under a slight load and labouring at this speed before it kicks down and the fault disappears immediately and doesn’t return at any other speed.

The oil was changed in mine last year, will give it a try in sports mode.

Managed to drive the car this morning to take the wife to work , so I tried sports mode on the section of road where I normally have the issue. Unfortunately the test didn't mimic the fault as the gearbox didn't change into 5th until 70 mph, where as the fault would appear in drive in top at 50 mph in it's normal mode.

When I've finished the jobs on the tourer , I'll have the autobox oil changed on the Connie to see if that makes any difference.