The P/N from above, #01-24730-004 is the Freightliner / Alliance # for the main serpentine fan belt. On my package it also had the #8PK1813 20-7620.
The little water pump belt is Cat #036-6775
Cat's phone # is 877.777.3126 and they'll need the engine S/N to help you.
Also, on a smart phone load app 24 7 direct. It's direct to Freightliner or call 800.ftl.help and it's supposed to be a 24 hour help line for broke down trucks. They can help with the belt question.
Having replaced the belt myself (I have the same 2005 39S Excursion C7 350HP) the belt is easiest to change if you empty the closet, raise the floorboard, and have two people, one on top and one on bottom to get the belt worked around the fan blades.
Also, if you haven't explored the closet floorboards a lot, on the left / driver's side behind and under the radio, there's a raised floorboard about16" x 20" where the engine air intake comes in from outside and goes to the air filter. It's a great place to store several sets of oil and fuel filters for both the engine and generator and spare belts - little things you need to have with you but don't use every day.
If you haven't taken up the floorboard before to get to the main engine, email me at trackrig@gmail.com or call me at the house at 907/272-5898 or on my cell at 907/244-0007 as their a pain if they haven't been up before.
If I find more cross reference #s for the belts, I'll do another post. The problem if finding someone open today. Napa, any Freightline, Cat or good truck should have them.
bill
