I need a diagram of how to route a 2004 chevy duramax serpentine belt on a duramax 6.6 LB7. with a dual altenater setup, thank you.

hope this helps? should do it for you.
https://www.justautorepair.com/multimedia/1-belts-diagrams/detail/129-diesel-belt-routing

Jeff, Check the attached links,instruction and guides, diagram for a serpentine belt, Good luck
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there should be a decal under the hood somewhere that shows the belt routing.

Here's your diagram.

Below is the master help link provided to go through belt routing diagram:---Timing belt,drive belt,serpentine belt,accessory belt,fan belt,engine belt routing diagrams for all types of car models?
Click the link below :----http://carbeltrouting.blogspot.in/2012/02/timing-beltdrive-beltserpentine.html
----------This will help.Thanks.

Hello ezzywaylogis,

Below is a diagram of the belt routing.



I hope this helps.

Regards,

Jerry

Fig. Accessory serpentine belt routing-4.3L, 5.0L and 5.7L engines without A/C




Fig. Accessory serpentine belt routing-4.3L, 5.0L and 5.7L engines with A/C

Fig. Accessory serpentine belt routing-6.5L Diesel engines

Fig. Accessory serpentine belt routing-6.6L Diesel engines

Hope this helps (remember to rate this answer).

You didn't list your motor size so please pick the applicable diagram:


Accessory serpentine belt routing—4.8L, 5.3L & 6.0L engines


Accessory serpentine belt routing—5.7L engines with A/C


Accessory serpentine belt routing—5.7L engines without A/C


Accessory serpentine belt routing—6.5L Diesel engines


Accessory serpentine belt routing—7.4L engines


Accessory serpentine belt routing—8.1L engines

Hi,
Here is the belt routine diagram

Hope this helps
Thanks
Smith.