I have a similar symptom, usually in 5th going uphill around 1500-2000 rpm. More often when at the beginning of a drive.
It was a constant problem the first day I owned the car, at 175k miles, and I took it over the mountains to come home.
There is something called Adaptive Transmission something, some software
driving aid that no one can explain.
There is a TSB the refers to "driveline shuddering", no other details and which says to reset the ECM.
P.

 

Have you tried downshifting to 4th gear or even to 3rd to see if the drivetrain runs smoothly at higher rpm, instead of shuddering in 5th gear going uphill at 1500-2000 rpm?

 

Yes. Downshifting to 4th usually clears it up, for a temporary fix, but I would like to figure out how to cure the cause.
Thanks,
P.

 

And I got the ATF fluid checked and replaced 8 liters of it and it looks good, and the car runs great overall. No relevant codes, no dashboard warnings, good mileage, good power, 175k miles.
P.

 

I have the exact problem described here.
Did the atf replacement procedure, went through 2 i/2 gallons.
Helped immensely but 3 days later the problem has returned.
Per this awesome thread I'll be inspecting all hoses and wires, cleaning the MAF and throttle body and trying that Fuel System Cleaner.
Wish me luck, can't afford to buy another car for the wife.
Especially since I need to rebuild the engine on my Sportster!

 

There is a Technical Service Bulletin that describes the complaint of "shuddering" with no details and which says to reset the ECM.
That process is described in the Service Manual in the section about disconnecting or replacing the battery.
This might be the fix, depending on what they and you all meant by shuddering. In any case it is cheaper and faster than any of the other solutions suggested above and you can follow those if this does not work.
I have not tried it myself. My shuddering has decreased since I first drove the car, maybe that is the ECM reprogramming to my driving style, which involves high mountain passes over the Sierras several times a year.
P.

 

Same problem


Did you sort this please?

 

I believe that it was the upper intake manifold not seated properly. I refit it three times to ensure that there was a good seal/fitment.
it’s kind of difficult to see, but the first two times I tried, i could see the upper intake gaskets peeking thru the bottom and top (inbetween). Once it was fitted properly, i couldnt see anything peeking thru and I had a good feeling that it was fixed. After the third time I refitted the upper intake plenum it ran great with no hesitation at 1500-2500rpms.
Hope this helps.