No one knows for sure how strong gorillas are. Some sources claim that gorillas are only 4 times stronger than the average man at pushing, and 8 times stronger at pulling(
www.allexperts.com), while other sources claim that gorillas have the upper body strength of up to 30 men and can flip cars with ease(Discovery Channel)!
The most reasonable source I've seen is from a famous primatologist who stated that gorillas are 5 X stronger than elite Human powerlifters at pushing and 8 times at pulling, and that when it comes to power(strength multiplied by speed), they have 10 X the power of an NFL lineman or Mike Tyson in his prime.
One thing is for sure: at least when it comes to pulling, gorillas are much, much stronger than any man. The reasons for this is that not only do gorillas have a lot more muscle than Humans, but a lot of their muscle mass is in their back. Studies have shown that the cross-sectional area of muscle in a gorilla's back is up to six times greater than a Human's. Ronnie Coleman in his prime probably only had twice the cross-sectional area of muscle in his back than an average man(which is really huge. Doubling your muscle mass is utterly insane!). The second reason is that the gorilla's shoulder joint allows it to focus pretty much all the strength of it's back muscles for pulling. A Human has a shoulder joint that only allows it to focus a fraction of the back muscles' strength for pulling. Humans have terrible leverage for pulling.
The much larger back muscles and superior leverage gives the gorilla a pulling strength over 20 times greater than an average man's and about 8 times greater than the World's strongest man. Chimpanzees can dislocate and rip a man's arm right off the sockets, and a chimpanzee has only about 20% of a mountain gorilla's power. This means that a gorilla could rip a bear's limbs from the sockets as well. This would be hard with a large grizzly due to the grizzly's very thick arms which wouldn't allow the gorilla to grip firmly, but it should be no problem with a black bear or smaller grizzly bear.
SUCKMYMUSCLE