I have covered the main points in my piece WWII Myths - T-34 Best Tank of the war but I decided to include here some interesting information from various sources.
Ability to maneuver on soft ground
The T-34 had wide tracks which gave it a ground pressure (kg/cm2) of 0.64 for the T-34/76 (assuming 26 tons) and 0.87 for the T-34/85 (at 32 tons). Low ground pressure meant good maneuverability on soft ground (at low speeds) but for many authors it meant that the T-34 could never become stuck in mud. The truth is that the T-34 had the same problems with mud as all other vehicles in the Eastern front.
‘The Das Reich SS Panzer-grenadier Division turned north, advanced on Belgorod, captured the city, and linked up with Grossdeutschland, which had now thrust beyond Tomarovka. Between these two points two German infantry divisions slowly struggled through the mud in their effort to reach the western bank of river. When our counteroffensive had begun there was still some snow on ground, but just before the Armeeabteilung reached the upper course of Donets a sudden rise in temperature created a severe muddy condition. All vehicles except those on the only hard-surfaced road in the area, leading Kharkov to Kursk, became helpless. Our infantry could still slog forty but heavy weapons and artillery were delayed and finally moved up only great effort. Even the T-34s of the Russian rear guards had become embedded to such an extent that we could not retrieve them until warm weather.’
Raus is referring to Manstein’s counterattack in the Ukraine in early 1943.
Interesting information on the T-34’s reliability (or lack thereof) during the Kamenets-Podolsky operation (Hube's Pocket) of March-April 1944 is available from ‘Tank Rider: Into the Reich with the Red Army’
From page 64
‘We were happy when tanks from our Brigade's tank regiment caught up with our battalion and we moved on as tank riders. We had just one objective — to capture Kamenets-Podolsk. Running a bit ahead, I would say that it took the Brigade two or three days to arrive at the town. Both people and tanks were tired; the vehicles couldn't take such stress either. Tanks stopped more and more often because of small technical breakdowns, especially broken tracks. Of course we tank riders assisted in tank repairs, so as not to fall behind the battalion.’
From page 77
‘We did not have many tanks left, and even those that remained had already used up their engine lifetime and were constantly breaking down. The tank that I was on with my soldiers also broke down. After a day-long stop in a village (we were already in the Western Ukraine), our tank stopped and would not move on. The battalion commander ordered us to stay with the tank and wait for it to be repaired. A day passed by and in the morning the tank crew told us that the breakdown was serious and we were stuck for a long time. I decided not to wait for the completion of the repairs, but to catch up with the battalion on foot.’
From page 79
‘After a brief rest the battalion received an order to advance and set up defences on the bank of Strypa river in the village of Dobropolie. Further to the west was the town of Bulach, where German reinforcements were starting to arrive. The Brigade was not capable of executing offensive operations. Its personnel was almost gone, almost all equipment was out of action. Out of 450 to 500 tanks of the 4th Tank Army at the beginning of the operation, the entire army only had around 60 vehicles, all with some kind of breakdown.’
The 5-speed gearbox controversy
Initially the T-34 had a 4-speed gearbox. The 4th gear could be used only on a paved road, thus the max cross-country speed was theoretically 25 km/h but in practice it was only 15km/h because changing from 2nd gear to 3rd required superhuman strength.
On later modifications there was a 5-speed gearbox which allowed for a cross country speed of 30 km/h. This equipment supposedly became standard from 1943 onwards.
However it seems that the T-34/85 tanks that were given to the Polish forces in late 1944/early 1945 still had the 4-speed gearbox. ‘T-34: Mythical Weapon’ by Michulec and Zientarzewski says in page 349:‘It was accepted, due to the available information in the subject literature, that the switch to the 5-speed transmission took place in 1943. However, the documents regarding the T- 34-85s delivered during the period end 1944/beginning 1945 (a month after their production) to the Polish forces prove that practically all vehicles had the 4-speed transmission. This applied to tanks produced by the No.183 Factory as much as to the ones produced by the No.112 Factory. The works on the new 5-speed gearbox along with the new main clutch design started in July - August of 1942 and paralleled the development of the T-34S.’