I've had the same problem with AAF, Trane, Lemonox (lennox) and others. The old motors are alot heavier and have longer cases. The replacement motors were lighter. After replacing several of these cheapies I looked for a heavier motor and found some that weighed twice as much and cost twice as much. Haven't had to change the heavy ones yet. had to modify a couple of brackets but the rpm, voltage, and hp were the correct ratings. I look for motors that are the exact voltage and rotation instead of the multi voltage-bidirectional units. They can be found. The multi tap motors are ok for smaller rooftops but the larger condensers need heavy stuff that can handle being switched on and off alot. Up here in AK with the low ambient, condenser fans get hammered. Good luck.