Typically, the T-34 is judged by design specs and assumed to be built up to production standards, or have post-war designs of the T-34 like 1946 models or later Czechoslovak 1950's models that were not war-production T-34's and did not operate under wartime production constraints.

The famed ~33 mph speed of the T-34 was mostly theoretical, in practice only achieving less than 10 mph. The engine (what people typically cite when they study the T-34) was a good design, but the four-speed gearbox was nearly impossible to shift and broke down regularly. The clutch was made with 22 steel plates at 1.5mm between engaged and disengaged because of a shortage of high-grade friction material in their plates, leading to this hilariously over-engineered solution. The clutch slipped constantly, causing strain and friction which deformed the plates, making it impossible to disengage, and so the T-34, despite having a four-speed gearbox, was in practice never engaged above second gear. The treads also had the unfortunately tendency to pop off when turning due to not hardening the pins.

The main gun, on paper, was an exceptionally well-designed weapon system, but in practice, poor shell production due to poor powder caused low velocity, and with poor accuracy to the aforementioned suspension problems, it meant that T-34's, in order to put down accurate fire, had to be still - useful in a defensive posture but less so in an offensive one, and even then, the shot was far underpowered compared to its performance under ideal conditions. The later 85mm main gun had better shell velocity, but accuracy was still subpar when not using solid shot. Worse, because of the Christie suspension used by the early T-34's, without the addition of turret stabilizers, the T-34's guns were incredibly inaccurate on the move, typically a T-34 would stop to fire, much like the Tiger (go Sherman gyroscope mount). Further complicating matters included not using smokeless cartridges, thus reducing visibility and accuracy, and poor optics (save for the gunner sight but not the gunner wide sight - two different optical systems) which made it hard to visually ascertain a target, and they would frequently fog up or freeze. At times, the T-34 production crews didn't even use mirrored glass for their periscopes, instead using polished metal, which as anyone can tell you, make for a blurry and almost-worthless optical system. This was largely due to the primary optical system factory being overrun in 1941, so this is less an issue with the T-34 and more an issue with poor Soviet engineering and production.

The tight crew quarters made for a bumpy, unwelcome ride - even North Korean soldiers were complaining about how cramped the interior of the tank was, meaning that tank crews performed poorly even accounting for training standards, they were simply exhausted before ever doing battle. Heaven help you if you needed to evacuate because the tank was on fire, something that happened with alarming regularity because the fuel tanks were kept inside the fighting compartment. The cramped conditions also made reloading a pain, reducing the rate of fire in situations where a high rate of fire was wanted; German tank crews were seeing double to quadruple the rate of fire. The barrel also had a problem with heat management which further reduced the rate of fire, APCR rounds would explode in the barrel. All in all, this drastically reduced the killing potential far below what was seen on paper.

The Soviet Union heat-treated the armor of wartime T-34's to an absurd degree, about 600 Brinell, leaving the steel hard but brittle, which left it vulnerable to being shattered or the joints popping - definitely a problem in any case. This brittleness created a significant risk of armor spalling - pieces of armor breaking off inside the tank and ricocheting around the tank cabin, causing significant crew losses. This bad production, much worse for the Soviet Union for other production factors. Soviet steel production was of poor quality, joints were often spot-welded from inferior material, and labor expertise was very low, meaning that solid frontal hits, even on its famed sloped armor, could tear pieces off the front. This led to a high rate of destruction, in 1942 the Soviet Union lost over half its tanks.

War production T-34's had a high rate of mechanical unreliability and failure - after one testing session, a Soviet major found that only 7% of T-34's had no mechanical defects and that the T-34 would break down after 50 km of travel. Production shortfalls meant problems like the hatches not receiving gaskets and thus, during any kind of rain water would leak into the cabin and short out the electronics. Tank experiments done on the Aberdeen Proving Ground with a Soviet T-34 tank engineer showed the wartime production unit to be prone to mechanical breakdowns. The high rate of failure and high loss rate also produced a strain in manufacturing, as new tanks and spare parts were constantly needed that would not have been necessary had the T-34 had better engineering.

Moreover, armor combat trials given after the war produced some surprising revelations regarding success in armored combat. In general, the best degrees of success in tank combat were the tanks that were able to spot first, fire first, and fire accurately. This in turn meant that success often relied on factors that are not in the typical tank information broadsheet and more upon other factors. The T-34, lacking a radio, meant that spotting had to be done with the head out of the hatch using flags, which made reconnaissance very important, whether that was done with cavalry, motorized units, scout tanks, aircraft, or even just a guy with binoculars and rangefinders. Most spectacularly, the Battle of Arrancourt saw Sherman successes over the technical superiority of the German armor by following g these guidelines. Delivering accurate fire meant that defensive positions simply saw superior tank performance, and this is backed by performance on the Eastern Front. After Kursk, when the Germans were on the defensive, their tank crews performed better, thanks to having observation posts, tank camouflage, and other defensive multipliers to ensure that they could deliver accurate fire downfield and not receive it in return. When the Germans did try to counter, and lost these advantages, their performance was much lower. This lack of a radio also meant that Soviet tank units were poorly organized, they didn't have the ability to focus and synchronize fire like other armor units. Some times, a T-34 would not hear enemy fire, or one tank would stop to fire while all the rest would continue moving...because they didn’t have a radio to inform each other that they had entered combat.

Success on the Eastern Front was dependent on a lot of factors, but the T-34's role is often outsized in favor of less interesting and simple but far more successful pieces of military performance. Operation Bagration, where the Red Army destroyed entire divisions, was enabled primarily through encirclement tactics enabled by Western trucks and excellent use of Soviet deep battle and deception tactics and techniques by excellent Soviet generalship from Zhukov and Rokossovsky. By keeping the Wehrmacht guessing, the Red Army was able to consistently achieve surprise, attack out of position German field units, and exploit the strategic depth of the German front, causing mass confusion and disorder that prevented solid defensive tactics (and anyone who says that the Soviet did human wave tactics to simply swarm the Germans until they run out of ammo is just wrong). Operation Bagration was one of the chief reasons why the Germans didn't reach fall back positions in great numbers and had a better chance forcing a stalemate on the Eastern Front as defensive factors overcame offensive ones.

What is most striking, and what I consider to be the chief issue of the T-34 being overrated (and a lot of reasons why I think things are overrated in general), is that the Soviet tanks do not appear held to the same standard as British, German, or American tanks. The German tanks are rightly mocked for being over-engineered and prone to mechanical failure despite impressive design specifications, but the T-34 is judged only by its design specifications as opposed to its performance - it's high rate of mechanical failure is never brought up as a detriment. This is relatively common with a lot of comparisons involving the Soviet Union, from economics, industrial performance, standard of living, or civil rights down to individual pieces of engineering. Most of this likely has to do with the highly-repressed nature of the Soviet Union, unflattering information was censored to prevent foreign and domestic criticism and what was available was often done for propagandistic purposes of the Cold War; plenty of T-34's observed by the West were the tank equivalent of a Potemkin village. Putin has similarly repressed any Soviet archives that depict poor Russian performance in the Great Patriotic War as "historical inaccuracy," preventing scholarly research from reaching the mainstream. Putin's not the only political manipulation preventing a revision of the T-34 tank myth, there's been a lot of bad Second World War revisionist history that vastly overexaggerates Soviet performance in the Second World War. This response simply swung the pendulum too far in the other direction, and now we're awash in bad history that tells its own untruths for multiple, usually stupid, reasons. And of course, we can't forget probably the biggest reason why problems with the T-34 aren't more widely known: it's boring. Engineering design specifications and performance reports are opaque without specialized knowledge and even I am mostly repeating interpretations of data that looks correct to my own engineering eyes.

Told better here with LazerPig. Careful though, there’s some crude and coarse language, but you’ll hear worse on primetime.

Thanks for the question, Anon, and thanks to anyone who managed to get through all of that.