Sounds like you're applying too much load to the axle while driving. We have customers complain about this with their e-lockers all the time. You should try driving on loose dirt (not pavement) while switching between throttle and coasting, and saw the steering wheel back and forth while trying to engage. This will allow the rear tires to slip a little and change the load, allowing quicker engagement. At least once a week I have to take a customer out in his Tacoma and show him how to engage the locker properly. Also, stopping and backing up sometimes works too. I think I've got a e-locker third member out in the garage somewhere and I can post up some pics of the internals- it'll explain a lot more than my rambling....
HTH,
Ryan
