My 93' BMW 740iL on occasion will leak oil out of the breather on the top of the transmission. This happened about a year ago and I removed and flushed the trans. oil cooler, topped off the fluid and it was fine until now. It never has happened with city driving, only on long open highway trips. Oil will drip down onto the exhaust pipes which causes a lot of smoke. I have already taken long trips, fully loaded, 95 degree days with AC on without problems, then will leak on cold days, no load in car. It at times will take 1.5 quarts to refill it again. The transmission from a driver's perspective works perfectly. No slippage, all shifts are smooth. Again it only will happen at highway speeds. Never around town driving. Any ideas? I am baffled.
