For some reason my truck keeps throwing the belt off, it has happened three or four times and usually wrecks the belt in the process. I dont see anything loose and dont hear or feel bad bearings. The only thing I can see is when I look at the crank pulley while its running it doesn't look like its spinning true. Any ideas fellas.

 

Spinning true? Like it's crooked or something? If so then you might need to get a new one.

 

I took a look again and I think the crank pulley is alright but i did discover something as soon as I start the truck the part of the belt that goes around the fan pulley gets pushed back towards the engine so maybe I'll start there.

 

Sounds good bud, good luck

 

i would def take a good look at the crank pulley.

 

How bout your tensioner pulley

 

I was about to mention the same thing.Some times when the roller on the tensioner wears, it will wear at kind of a slope where the belt will slide off the roller while the motor is running.I've seen this on the big rig cummins motors. good luck

 

Hey fellas thanks for the responses i think it figured it out i replaced the tensioner pulley after pulling fan water pump and inspecting everything.

 

I have seen the tensioner pulley cause this before, as well as the crank pulley! Start with the tensioner its cheaper and easier