Evening.

In another thread I talk about a problem with my harmonic balanced failing. Now the rough idle when stationary in D is getting worse. I’m suspecting I may have a gearbox fault.

It seems to only happen when the car is warmed up, my initial thinking was as the harmonic balanced rubber warms it loses stiffness and vibrates with the engine under load. Prior to this I thought it was an injector issue causing a rough idle.

This evening I’ve noticed another issue which was a lightbulb moment

While creeping slowly in D or R, ie: parking, I felt the car surging ... as if I was lightly tapping the brakes every second.
This then rang a bell with me, i previously had experiences on the motorway when cruising that occasionally I would feel a very very slight and sudden deceleration as if once again I had lightly tipped the brakes.

Has anyone experienced issues like this before??

I’m very concerned that it is the torque converter on the way out but hope fully something simpler like the valve body seals leaking and fluctuations in valve body pressure when warm.i changed the fluid and filter a year ago but left the seals un disturbed. It was just a fluid change not a flush, the car drove so well until recently.
I have the typical harsh downshift from 2 to 1, which also tends to point towards valve body seals

Any thoughts and advice is hugely appreciated.

Cheers,
John