http://www.onwar.com/tanks/
13.7 for the Sherman A3 and 13.9 for the Tiger I
They also give a road speed of 42 Kph for the M4A3, which IS better then the Tiger, I think. There are several version of the Sherman, differentiated mostly by engine, IIRC. So it would make sense that the speed varies by model.
Working with a rusty ol' shot to shit memory, I think most of the M4's went to the limeys, the A1's were pretty much split up between all the allies, with the Canadians and the Brits preferring the cast hull. The A2 had the Diesel and most went to the Marines and minor allies, while the A3 was issued to US Tank Battalions.
Tactically, you should NEVER fight German Armor with Shermans. Hide your Shermans and call in the Jabo's. If you don't have some P-47's orbiting the battlefield, don't play that game. If the Jabo's were grounded the ground pounders took the day off. Patton went nowhere without the 9th air force. watching over him.