Joe, My brother had this same problem with his 318i. He did not do anything to it untill the other trans mount broke, then the engie mount broke, then he drove it for 100 plus miles with the engine turned about 15 degrees clockwise. So DONT WORRY your car will still drive. ha ha ha . I would check BMP or Rocky mountian Motorworks for two new mounts. I think mine were 10 bucks or so each. It was pretty easy fix with a 85 318i which was given to me for FREE from my brother. Just make sure that you fix this thing quick or it can destroy your trans if it shifts out of gear at 4 grand. IF your poping out of gear now it could be due to the mount.
You are putting torque on your shift linkage due to the broken tranny mount and it pops out of gear. I bet
Feel free to email me for any questions you may have..
Rob

I've been having trouble with my Trans lately. It's been slippen out of gear(usually Drive) during the cold weather. I've changed the transmission fluid and It's made no change in the symptoms. I've had this clunk in the rear for about the past few months and I always thought it was something with my Differential but I got under the car yesterday and and took a look at my transmision mount and it was Shot to Shit. I mean the entire mount is totally destroyed and the trans is resting on the backet for the mount. Does anyone think this could have contributed to my trans problems? Anyone have any tips on changing the trans mount? No parts stores in my area have the mount so it looks like I have to get it from dealer or Order it online. Any Sugestions?? Thanks in advance.