The inconsistancy of the gear boxes...ok easiest way to put it is that you would have to shim either the motor mount and/or the gear box in order to get everything to line up square. The gearbox's were only off by a few thousandths, which is probably way inside their tolerance. Problem is when you match it up to something else that wasn't made in house at AE you might have a few thousandths here and then a few thousandths on the BMI end and that adds up. I know that it took me a long time to get it just right but when I did, it was perfect.