Im gonna chime in on this even though Im not 100% sure. In my TE there are literally at least 6 electronic interactions that must take place before the truck allows you to engage the locker. We're talking tranny sensors, t-case sensors, ABS sensors in addition to the numerous in-cabin switch position sensors. It is possible that these sensors can be accessed by someone who can decipher factory wiring diagrams, however, it seems like a PITA in a cost-benifit analysis. Before I tracked down my 4r I entertained the idea of a '99 4r either with the factory locker or retrofitting a 3rd gen locker to a non-stock-locker rig. The cost was ridiculous and was not without mechanical difficulty that exceeded my comfort level. Solution to your problem? Aftermarket air lockers, from reputable dealers such as ARB will give you a robust, on demand locker, while bypassing all the electronic 1's and 0's that can cause you much headache. Are they cheap? Nope. Are they worth it? Thats up to you.