my son's GF bought my 92 740 turbo wagon. they are replacing the worn motor mounts, and tells me the metal band around one of the new mounts broke... whats that band even do?

 

I'm taking an educated guess here and say it's probably a "Ground Strap" to complete the circuit for the Fuel injectors, alternator, ignition.
Back in the day I use to use a short battery cable to do the same thing and bolt it the engine block and the frame.

 

I was told by a Volvo tech that it’s a safety strap in case of a collision, it prevents the engine from falling out of the car since these mounts are meant to sheer in the event of a severe front end collision. This was in reference to a 2004 s60 and they have similar mounts. On that car they are braded cables however.

 

kinda hard to call a transverse mounted FWD similar but I know what you mean.

 

Different car completely, yes. but check out the mount:

 

yeah, the front mount on transverse FWD engines is similar... I bet the rear mount is totally different, looks more like a suspension bushing as its the equivalent of the thrust arm on the rear axle of a RWD live axle car like a 240/740/940...