Yeah, you're just getting some engine braking, something sadly lacking from most cars with an auto box. It does sound like it may have initially been a bit 'off' until they cleared the adaptions. The ZF 6HP28 is a pretty sophisticated piece of kit, and in conjunction with the ECM and the car's various sensors it does some nifty things, like skipping up to 3 gears if appropriate, and delaying shifts if you're cornering or ABS or traction control are operating.

 

Mine are pretty noticeable as well especially in Sport mode as the the engine "blips" and the car surges a bit due to the higher revs.

 

It's interesting that being the originator of this thread, I am driving an XF loaner today with 2600 miles that exhibits the very characteristics that my first post mentioned. I might have driven a total of 20 miles today where there was one instance of the car downshifting extremely hard to the point that I was startled as I had the radio on. I have a feeling that each owner of the ZF 6HP28 transmission might have his/her own distinct shifting pattern. These ZF transmissions are not very consistent as to how they will downshift at different times. That might be why I am hearing about clearing out the files in the TCM almost like a maintenance item as in changing oil. It's like rebooting our computers when we get a glitch and seems to be the nature of this beast.

 

My 2012 XF does this lurch. When downshifting from 3rd to 2nd it is the most evident where it feels like the revs were not match giving the car a slight bump/jerk in speed.

I got my TCM updated and my PCM reset. After the update it was still pretty harsh but my breaking was better. After driving it softly and putting the car in dynamic mode the car started shifting better. It started 'learning' my driving patterns maybe.

I would also many times down shift using the paddles just to blip the throttle. I blip it at 2k rpms on all gears except from 3rd to 2nd. If I downshift from 3rd to 2nd at 2000 rpm I get an evident lurch (engine break). I then always downshift at 1500 rpm and got pretty smooth shifts.

I feel that manually shifting it using the paddles (not S mode but drive mode in dynamic setting) has helped. Maybe try it your self and see. I just got my car's PCM reset again recently as I tried to eliminate the lurch completley but I am now convinced it is a ZF characteristic.

These ZF 6 speeds are pretty old but amazing technology. I would recommend downshifting manually and seeing at what rpm it lurches and at what rpm it is smooth, then keep doing it to make the transmission learn.