I'm six months into owning a 1998 XC-70 with 176,000km on it which manifests
two similar driveline behaviours:

1)  At a stop with foot on brake for more than a few minutes, I can almost
always get a minor "bump", which feels as if someone has tapped me from
behind with their front bumper..... no movement, no dip in the tach, and
this has happened again in particularly long stops for gridlock.  Has been
doing this the whole time I've had it, and

2)  For the last several days, I've gotten quite a "thump" which seems to be
from the drivetrain, but occurs while cruising between 80-100km/hr.  No
acceleration, no kick-down, just steady load/speed.  The third time this
happened, the driveline seemed to slip for a second, before catching back
up... but I was unable to see any change in the tach or speed.....  These
episodes last only an instant, and give the impression I've run over
something (but with only one wheel/thump).  Tranny functions crisply through
anything I throw at it otherwise.  Other than startling me, there seems to
be no other effect.

Tranny was flushed completely at 162,000km.

Dealer had car in shop and on the road today... no abnormal codes, performed
flawlessly on the test-drive.  Replaced the LF wheel-bearing, which was
likely coincidental, and *did* note the lower engine mount to be separating
(I think this an unlikely cause...).

Any ideas/experience from the cognoscenti ?

Merci,

Kevin