95 Blazer Need Help

i have a 95 blazer with the 4.3 vortec W code. i am not sure what trans is in it but i have a problem when i put the vehicle in drive it really slams into gear sometimes chirping the tires it also has a late shift on every gear even overdrive. the trans fluid is a good color and does not smell burnt at all it has 187,xxx miles on it though, could this possibly be my u-joints and i also am missing a motor mount on the drivers side. i also have a second problem with my brakes sometimes when i hit the the brakes when going in a trail i hear a loud buzzing like sound and a vibration at the pedal. any input will be greatly appreciated