Which 9 speeds can be converted to 13’s?

Most all Rt,Rto, 9 speeds can be converted. But you need to know what version your building. Short end of this, any capable trans shop can help source the parts. I do think I would disassemble and verify any used trans before ordering parts. Who know what someone could have used on last rebuild.

The C, or convertible trans was a marketing gimmic. It was a 13 speed without air valve. Big sale to fleets like Werner. They would add air valve, change shifter knob, and sell used truck to a OO with a 13 speed.


I have no knowledge to add on Rockwell, or Spicer.

 

H&W did the same thing, trucks had a 13 spd transmission with a 9 spd shift knob. Most of us carried a 13 spd knob in our clothes bag, change it across the state line and then change it back end of the week before getting to the yard…..

 

Less than built 13 speeds. Your TQ is more important than HP. Most big TQ motors never got a 9. Unless someone was the cheapest SOB around. Your gonna get a 9, and build it to your TQ for your application. Big power and going fast had a cost, how fast can you afford?