in his sefer on ketobos rav elchono wasserman asked rav chaim about the tosfot on daf 8 in ketuvot re: rav tana hu paleg and how come we dont hold like rav yochanan but hold always rav tana .....

rav chaim ans that rav was entitled to disagree with an amora and said the ramban in baba kama daf zadek zayin lists many cases were a tana disagreed with an amora.. i also looked in the kesef mishna on hilchot mamrim perek 2 and he seems to say that the rambam holds that a tana can disagree with an amora

question: is the above correct ..

i cannot seem to locate this ramban or the qoute from reb elchonons sefer on ketobot can you please help

also is my reading of the kesef mishne coreect... i also saw the biur hagra say that a tana can disagree... but today no one can disagree with the gemorah going back in time

akiva glasenberg, toronto canada