New Alternator -

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post #1 of 8 Old 11-07-2012, 10:15 PM Thread Starter
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New Alternator

I need a new alternator for my 4.0. I'd like to get a higher output one but and I'd rather buy used for a cheap fix. I've been reading a few threads and some have said you can take an alternator from either a dodge durango or a 5.2/5.9 zj and the brackets will fit. Is this true? if so what year does the durango have to be?

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post #2 of 8 Old 11-07-2012, 10:16 PM Thread Starter
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Also will the cables fit or will I need to do some splicing?
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post #3 of 8 Old 11-09-2012, 04:18 AM
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A stock 4.0 is not the same as a stock 5.2/5.9 (mounting wise) but can still fit in a 4.0L with some slight modifications. However, unless you're running an electric fan or something other that will drain extra current from your battery, I would highly recommend just sticking with a stock 4.0L 90A. The biggest reason is because the amperage is different: A stock 5.2 is rated at 136A and a stock 5.9 is 150A. Unless you upgrade your battery terminals, wiring, and connectors that run to the alternator, you may not notice a big difference in the charging system, since the stock wires are not rated for that kind of current. I know they're not the greatest alternators, but I run a NAPA 90A in my 4.0L and I haven't noticed any problems yet. The voltage remains fairly constant.

However, if you do go through with the Dodge Durango alternator, make sure it's from a 5.2 Durango, and not a 4.7. Although I've never tried, I can't imagine that a 4.7 alternator will fit in a 4.0L

Hope this helped, and be sure to keep us posted

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post #4 of 8 Old 11-09-2012, 08:12 AM
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Keep the pulley and the black isolator from your old alt. Get a 117, 136, or 150 amp from a later ZJ. The V8 pulleys are 7 rib and the I6 are 6 rib. All Denso alts are basically the same, except there is a large case and small case, but I think both will fit.
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post #5 of 8 Old 11-13-2012, 12:04 AM Thread Starter
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The cables shouldn't be too hard to upgrade right? I'm sure I need to run more 90A alternator because when I slow down the voltage drops a lot and the lights go dim. It does it mostly when it's cold because of the blower motor and the lights are all on at the same time.
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post #6 of 8 Old 11-13-2012, 12:29 AM
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Your 90A alternator should surely handle the blower motor and all the lights on at the same time w/o the lights dimming when slowing down. Sounds like you should remove your alternator and take it in for a free test to see how many amps it's putting out. Either your alternator is not putting out enough amps/voltage or your connections are bad/corroded. Also check to make sure the belt isn't slipping.
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post #7 of 8 Old 11-13-2012, 05:09 AM
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Belt is probably slipping big time

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post #8 of 8 Old 11-20-2012, 12:31 AM Thread Starter
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Alright I'll check the belt and make sure it is ok.
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alternator , swap

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