"some major differences" is correct and usable in written English.
It can be used to describe significant distinctions between things or ideas. Example: "There are some major differences between the two political parties' stances on healthcare reform."
In the following, we briefly discuss some major differences in coding potential observed between the different photosynthetic eukaryotic organisms.
However, there are some major differences between the two studies (apart from a different sized patient population).
Nevertheless, some major differences should be pointed out, and the trigger of carcinogenesis seems to be different from that in CRC.
But there are some major differences between the Tories and the Lib Dems.
This environmentally conscious off-road event is reminiscent of "The Amazing Race," with some major differences.
For all the similarities, there are some major differences between then and now, particularly the changed political landscape for gay Americans.
But we're separated from each other by millions of years of evolution, so there are some major differences between their brains and ours.
"Our bill, the House and the Senate bill, had some major differences, which we're hoping now to reconcile," Ms. Pelosi said.
"I remember at one point making a careful table of how many people each type of dinosaur had eaten in 'Jurassic Park' — both the book and the movie, of course, because the list of who dies has some major differences".
That measure is broadly similar to the Senate legislation, but there are some major differences that would have to be resolved before a bill could reach Mr. Obama, and that would almost surely push the process into next year.
Granted that in economic matters, about which even economists cannot agree, there may be little difference, but I would like to point out some major differences in other areas.
