The underdrives are one of the best seat of the pant's mods you can do. They are easy to install, but to get the pulley off the Alt. it is best to use a impact gun, I have heard some garages will take them off for you for free, you also need to put the new pulley on woith one takes 30 sec's with a impact. As for charging, I have wen't through 2 65amp alt, and I did have low charging but it has seemed to be better with this last alternator and ignition switch. A lot of people leave the underdrive alt pulley off and keep the stock pulley if they have charging problems, I don't think you would have any prob's if you have a 130amp.
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