Mine does that too ! Surges in 5th and 6th at 50-60kph . Only when cold and only when under light to medium load and only for the first 7-10 mins from cold,
Chuck it in 4th and it's fine , wasn't shore if it related or not but it seems to
Sort itself out at the exact same time as the sistums readiness check fineshes ,
P1000/p1111 could this be related or coincedince ?

Not a good selling point , but luckerly it's not for sale!
I will be swapping out the tranz fluid in the next month or so
And will be using lg6 in hope that it might help !
The last owner said that it had done it since he bort it
He owned it for 30,000km and said he had ATF change not sure
Wot thay replaced it with , and also had a
Software update twice . And one of the updates fixed it for less
Than 2000km . It's certinly not the described lurch . It feels like it's
Repeatedly trying to lock up the cluches and fails to do so ! Almost like it's going from
5th to 6th to 5th to 6th so on and so forth ----!
Once it's goten over it 10mins later she's away perrrfect silky tranny!
I suspected torqu converter but realy hope it's the rong fluid in there ,
This is the first time I have seen the surge (not the lurch) documented!
May have mist it but have been searching ! Shame for us there is such issues
With these cleaver zfs but am pleased I'm not not the only one with the freek
Show transmish!!

 

P1000/P1111 are something else - read workshop manual or previous threads.

Yours sounds like the TSB and many threads on the TC.

 

Here are some results for Mercon SP in a ZF6HP26: I have been using it for three years now. No problems.

 

I put Redline D6 in mine when I did the whole transmission service with all the parts. It was far cheaper and it's good stuff. There are several alternatives out there. I just got a good deal on a case at the time.