You're probably talking about the Losmandy Hursts (just a guess, but that was the outfit using hursts for about 12 years). Even if your mopunt says celestron it's likely a Losmandy if it is sporting Hursts.
The Hursts were criticized (and I personally verified on my own G11) for having visible vibration at high magnification. They were eventually replaced by the SAIA motors that you can get from Losmandy. While I prefer to run two motors of the same make on my mount, there is no *real* need to have two Hursts. You could throw out the bad unit and put the other one on Dec (if the good was is RA).
But really you don't want to go the other way around, if your RA unit is dead you don't want to put the dec unit on--get a better one, an SAIA or the new ones.
Because the the SAIA motors, which are very dependable, were replaced by Losmandy with yet another brand, whose name I don't know. You'll probably see it on their web site.
So in my mind a Hurst failure is really an opportunity for a needed upgrade. But I am curious: stepper motors are extremely tough, and don't fry easily because if they hit tight spot they cant move through or are over loaded they just stop. That is a feature of the design. No burn out. So I'm wondering what went wrong.