The Falaise Gap: Residents of Avranches watch vehicles belonging to a US armored unit move through the street. Some of the destruction caused by the shelling of the town preceding its capture can be seen in the background.

Armor moving through

""In December 1944, the US 7th Armored Group assigned to the 30th Infantry Division the task of using a new, untested, weapon system-the T-34 - in support of an upcoming infantry assault. Plans called for the 29th Infantry Division to establish a bridgehead over the Roer River in the vicinity of Julich, Germany. The 30th ID was to cross the river behind the 29th and launch an attack to the south-east. The zone of the 30th ID included Staatsforst Hambach, deemed to be an outstanding obstacle with the enemy dug in on the north and west side of the woods. It was planned, therefore, to saturate these woods with rocket fire just prior to launching the attack. 
 The T-34, nicknamed the ‘Calliope’ was a 60 tube rocket launcher firing a 38.5 pound High Explosive rocket out to 2,900 yards and was designed to fit on the turret of the M4 Sherman. Twenty-two launchers were to be mounted on tanks of the 743rd Tank Battalion. In addition, the 3508th Ordnance Medium Auto Maintenance Company was designated to design, construct and install a suitable mount for the T-34 in five captured German halftracks.""
taken from fb/Erling baldorf

SdKfz 251 w/Calliope, 1944

Results of ballistics test on the differential housing of an M-3/M-4 