When swapping to 9.25 posi and reusing old ring gears. Do you need to use the starter ring gear that sits right behind it? What does it even do? I’ve seen several people not have them on there differential. Do I even need it?

 

You may be referring to the ABS tone ring, aka exciter ring. Look that up and see if that is the part you are asking about.

 

It’s the starter ring gear or tooth ring gear sits right behind the ring gear.

 

That's the tone ring for the rear wheel speed sensor, and yes, that absolutely needs to be in there.

 

ok thanks

 

The gear in the differential has nothing to do with the starter. It sends a signal to the ABS sensor. Since you have that then your truck has rear wheel anti lock brakes. Trucks without that gear do not have RWAL.

 

ok yeah that makes sense. Thank you