2021 ram 2500 Alternator Belt Question

[JustARam22]

So I purchased a upgraded 400amp alternator for my 2021 ram 2500 6.7l.

Per the manufacturer the new alternator requires a belt that is a 1/2 inch smaller due to the pulley size. I think it's stupid they don't sell a belt with it but here we are.

Does anyone know the size of the OEM belt. I am having a ship to do the swap so just pulling it and bringing it with me isnt the most ideal option. Any help is appreciated

 

[AH64ID]

Why go to a single 400A alternator when your truck is wired to control a 2nd alternator? There aren’t many benefits to a bit single vs smaller dual alternators.

With duals you don’t need an off size belt, you get more amps at low engine rpms, the alternators run cooler, and you get redundancy.

 

[JustARam22]

Not the route I wanted to take....

It's still an off size belt compared to single alt, even though it's OEM.
It's more expensive compared to a single alt.
More rotating mass
More drag on the motor
Less points of failure

 

[AH64ID]

Your bottom bullet point out weighs all the others. If a big single were a better option then that’s what OEM would go with. I’ve been around too many folks with premature failures of oversized alternators to consider them a viable option.

I highly doubt the drag/mass is measurable at highway rpms/loads.

There are so many of these trucks with dual alternators it’s not an off size, this configuration has been around for 10 model years. It’s a far more popular option than the Jacobs exhaust brake was on the 3rd Gen 5.9 and those belts were easy to source.

Were you able to find a 450A fuse to replace the 250A OEM one one the alternator wiring?