Mine seem to work fine. The express-down is very fast, almost too fast, as I still need to get the hang of just opening the window a crack without it trying to go all the way down. On mine, just pressing it normally causes it to drop like a rock. I have to barely touch it in order to "manually" control the speed. As far as coming back up, the windows are pretty fast also.
I don't think you would be able to retrofit another manufacturer'* motor to fit your door. I could be wrong, as many auto makers buy their common parts from third-party OEM'* nowadays. In any case, the physical mounting ot the motor and bracketing inside the doors are probably different.
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