This may vary with your vehicle, the repair was done on my 08 impala with the 3900, should be the same or similar process in your 06 or 07 mc with the 3900

I got mine locally as online couldn't beat the price

Tools needed,
3/8 ratchet
Small extention
15mm socket
15mm wrench
15mm stubby wrench (if you have one)
10mm wrench
10mm wrench
Piece of pipe(not required but helpfull)

Step 1 pop the hood
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Step 2 take your 10 mm and lossen then removed the + battery cable
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(This Is a good time to clean your terminal if it is corroded)

Step 3 unbolt with your 10mm the radiator reservoir and set to the side
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Step 4 with your ratchet lossen the belt and pull off alt
(You will see there is a square hole in your tensioner that is ment for a ratchet)
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I use a piece of pipe for extra leverage
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Step 5 undo the 10mm bolt that holds the power steering line
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Step 6 take your 13mg undo the power wire and plug from the altenator

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Step 7 remove the 3 15mm bolts holding in the altenator
This one is the easiest, I just used a 15mm socket with small extention and 3/8 ratchet
(I used the extention becuase the power steering was somewhat in the way to do it without)
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This one was the hardest, this is where a stubby 15mm would be nice, this is the backside bolt and doesn't leave much room between the firewall and bolt
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This one wasn't the easiest either but could easily get it with a wrench
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Step 8 pull it out and make sure it is the same as your new one
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Step 9
Reinstall and bolt it down
(See step 7 and reverse)

Step 10
Reinstall install power cable and plug
(See step 6 and reverse)

Step 11
Re install power steering line mount
(See step 5 and reverse)

Step 12
Re install belt
(See step 4 and reverse)

Step 13
Reinstall resivour
(See step 3 and reverse)

Step 14
Reconnect your battery
(See step 2 and reverse )

Step 15 close your hood and pat yourself on the back for a job well done

 

You did a very nice write up, great accompanying pictures. I'm sure this will help out someone, there is just never to much information. Thanks for the extra effort here.

What project is under the car cover??

 

Saw a void thought I try to help fill it, not many mcs with the 3900 but figure I have a similar car that will have the same or similar process I can fill that void

That's the 84 wish I could be doing more work to that but can't right now