Gorillas don't have much for protection. The bear has 4" of fat "armor". The gorillas won't be able to bite or tear flesh.
My thinking is that if the bear is able to grab one of the gorillas, it will be disabled pretty much instantly. Unless the remaining gorilla(s) can press their momentary advantage while the bear is distracted, it's just going to rip them apart one by one.
1v4, they might have enough clout to keep the bear immobilized long enough to kill it.
Yeah, with adequate coordination, the gorillas should prevail in a 1v3. But I think they tend to fight more like individuals than as a pack.