OD 13 speed

That 13 direct is a medium duty trans that has a deep reduction. It's I run the RTO6613 in my mechanics truck. Same pattern but big hole against the dash. The RT and RTO6613's were popular behind the 238 and 318 Detroit's.



A true double over 13 had 3 ranges above direct. The 5 series and 6 series had overdrive in the back box. That was a weak design created alot of heat as well as gear howl. Too much torque strips the shift collar on the overdrive gear pretty quick. A 14609B has a good low reverse as well as low hole with a .73 final ratio. Put a RTO14613 rear box on it and you have a factory RTOO gear set. .62 overdrive. If you made some gear changes in an RTO14613 you could get to .62 up top but you also ended up with a racecar reverse that was junk.


The 7 and 9 series transmission have over drive in the front with a 13% under drive in the rear box. Just an all around way stronger set up