The backfire retort on the Sherman was like an aircraft engine turning over (well it was an aircraft engine so its not surprising) My grandfather (6th Panzer division and later Panzer Lehr) told stories of laying in wait with a Panzershrek and when the backfire of the sherman came they would pound it with a deluge of rockets or call in artillery strikes
The Americans had plenty of time to study war in Egypt and send observers to the Russian front to see the progession of tank warfare and push their development towards a more battleworthy design... If I was sent to the hedgerows of Normandy or the plains of Italy a sherman is the last place I would want to be considering the knockout ratio against you is 5 to 1.... 4 tanks are going to die before you take out the tiger
Actually, only the M4 & M4A1 used the modified gasoline aircraft radial engines among the Shermans. The M4A6 used a diesel radial derived from the Wright R1820, but it was a fairly rare variant. It, and the other diesel Sherman (M4A2, powered by 2 GM L6 diesels) were very rare in US Army service, as Army Ground Forces decreed that diesel-engined M4s in US Army service were not to be used outside the US for logistical reasons; most were either given to the Marines for use in the Pacific (the Navy having most diesel-related logistical & support assets), or were transferred abroad under Lend-Lease, largely to the Soviets and the British. The M4A4 used a weird multi-bank 30-cylinder engine (5 Chrysler L6s thrown together to use a common crankshaft); most of these were transferred to Britain under Lend-Lease. The variant ultimately preferred by the US Army was the M4A3, which used a Ford OHC gasoline V-8, which was more powerful & reliable than the radial engined variants, and started supplanting them in service between mid to late 1944. Shermans retained for post-war service by the US were versions of the M4A3.
Secondly, the Sherman was a late 1940-early 1941 design frozen for mobilization production, prototype in August 41, series production in October, and would have been quite capable of dealing with the Axis tanks then in service. (Incidentally, the 76mm Sherman was about as capable as the T-34/85 in actual combat.)
The problem was that Allied intelligence failed to anticipate that German AFV design would essentially leapfrog a generation in 1942 (both the Tiger & Panther being 1942 designs), and when they first appeared, thought that they were limited production variants intended for a few special units. This was compounded by the intransigent insistence by Army Ground Forces that the job of fighting enemy AFVs was that of the tank-destroyer, not the tank (which was to support the infantry and exploit breakthroughs according to doctrine), and thus the 75 mm Sherman was all the tank the US Army needed, while any changes to armament or alterations to increase survivability would unacceptably disrupt production. Army Ground Forces used these arguments to block production of the 76 mm Sherman (inferior HE round to the 75 mm and would encourage tanks to fight other tanks contrary to official doctrine) the M-26 Pershing, and proposals for upgunned variants of the Sherman, such as the Firefly, despite mounting evidence fron 1943 onwards that their assumptions were sorely mistaken and demands for more powerfully armed tanks; it took the personal intervention of Gen. George Marshall to get any of these built and in service, and even then, Army Ground Forces dragged its feet, delaying the combat introduction of the 76 mm Sherman until July 1944, and the Pershing until early 1945. The situation with Army Ground Forces' resistance to improving the Sherman could be somewhat analogized to the USN's struggles with the Bureau of Ordinance over torpedos.
Despite its issues, the Sherman did manage to get the job done, and there are much better candidates for worst tank of WW2- the Ferdinand/Elefant for the Germans, the US M3 medium & M22 Locust, just about anything the Japanese sent into action, the Soviet T-26, T-28, T-35, & BT-7 (well past their expiration date by 1941) & KV-1 (well protected for 1941 but slow, unreliable & clumsy, difficult to produce, and had the same firepower as the 76mm T-34)