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Old 08-13-2012, 10:03 AM
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Replacing Bearings in 12si alternator

Yea, it would be easier to replace the whole unit but I'd like to rebuild one of these completely for the experience. I've pull out all the guts and cleaned stuff off and may end up replacing the internals with a mad elctrical 105 amp kit for the 12si. But I want to replace the back needle bearing. How do you get that one out? The front bearing and retainer are clear enough it appears.
It's that back one that has me wondering.
Plus this is a more basic truck from an accessory standpoint and the 78 or 94 amp 12si should be more than I need really.
Thanks,
matt

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Old 08-13-2012, 04:24 PM
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Originally Posted by red82c10 View Post
Yea, it would be easier to replace the whole unit but I'd like to rebuild one of these completely for the experience. I've pull out all the guts and cleaned stuff off and may end up replacing the internals with a mad elctrical 105 amp kit for the 12si. But I want to replace the back needle bearing. How do you get that one out? The front bearing and retainer are clear enough it appears.
It's that back one that has me wondering.
Plus this is a more basic truck from an accessory standpoint and the 78 or 94 amp 12si should be more than I need really.
Thanks,
matt
That bearing is a slight press fit. The easiest way to remove it is to get a round wooden dowel slightly smaller than the shaft hole. Wrap elecrical tape around the dowel until it is a snug fit in the hole. Put some grease in the hole and using the dowel, tap it in the hole. Basically what you are doing is creating hydraulic pressure behind the bearing, pushing it out. Keep adding grease and repeating the process until the bearing comes out. When you put the new bearing in, put the new bearing in the freezer for a few hours to "shrink" it, it should fall in or lightly tap it in. Once in, let it set at room temperature so it will expand and fit tight in the bore.
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Old 08-13-2012, 04:59 PM
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Easy to do. Take your clean red shop rag and while opened hold the housing and coil against your stomach. With a 3/8" drive extension and a inverted 5/8" socket drive the bearing out. Set the housing on your bench outside down and tap new bearing into the hole With a inverted 11/16" socket on a extension finish driving the bearing into place. Piece of cake.
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Old 08-14-2012, 05:31 AM
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12si bearing removal

Thanks for the response. I did basically the same thing to get the pilot bushing out of the crankshaft. I'll give it a try. Which makes me wonder if the wet toilet paper trick would work here like it did with the pilot bushing?

matt
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