The most informative and comprehensive page that we have found on the overdrive originally designed by Warn is on the CJ-3B Bulletin Board here:
https://cj3b.info/Tech/Overdrive.html
The overdrive is not as complex to install and remove as most people would believe, even after looking into it. We understand that we do this weekly and even daily, but as far as gearboxes go and especially as far as adding one extra gear to your drive train goes, the overdrive is in comparison dramatically easier to install/remove and work with in general. We are here and happy to help with any questions via E-mail and phone if needed when installing the units.