I installed a $68 reman from NAPA on the passenger side front which leaked and vibrated. It did solve clunky shifting though. Tried 3 seals before I lost patience and spent $448.28 on a BMW reman. But not before we drove on a 1600 mile trip smelling and breathing burnt gear oil...yuck. BMW didn't want my core but NAPA was happy to refund my money. No leak, smooth running and smooth shifts. i've read here that some have had success returning and trying a different axle. But like I said I ran out of patience.
BTW the NAPA axle where the seal rests was 1.731" in diameter.
The BMW axle measured 1.730". That seemed odd. All I can come up with is the NAPA axle must be bent, providing just enough run-out to let the oil leak...that could explain the vibration too.
Food for thought. A lesson I learned in the aviation business a hundred years ago, if it's cheap, it's a piece of sh#*! 9 times out of 10 there's a reason the correct part costs more.