well, i am home, looking at the Osprey Publishing New Vanguard
"88 mm FlaK 18/36/37/41 & PaK 42 1936-45"
(John Norris - Illustrated by Mike Fuller)
that is almost certainly a 88 Flak 18
entered service in 1933, 2 section barrel,
barrel an L/56 type 53 calibres in length, overall length 4.664 meters
(tho i would think an L/56 would be 56 calibers in length, but it reads as above)
gun carraige fitted w/ 2 pairs of bogies for travelling.
on the Flak 18, the two bogie sections are not identical as they are in the Flak 36 and later versions.
also in later versions, each section had a barrel support so the gun could be towed facing in either direction.
(on the Flak 18, they are ALWAYS towed w/ the barrel facing the prime mover
which perfectly matches your photos!)
later barrels were 3 sections.