DIE HARD NISSAN

I'm new to this site, but found lots of good stuff the past couple days just browsing. I'm experiencing the trouble many have been having with the auto locking hubs, namely the hubs not freeing up after 4WD is disengaged and starting from a cold start. On my 1995 V6 Hard Body Extended Cab I get the buzzing/grinding noise from the passenger side hub and the clunk when coming to a stop. The same thing happened with my 1989 (also passenger side). On that one I cleaned out the old grease and re-greased and that took care of the problem. Tried it on the 1995 but it didn't seem to work. Tried putting the 89 hub on the 95 but it has the different axle size/spline count thing going on. Considering putting manuals on seeing as it seems to be an easy conversion and maybe it will take care of the other problem I'm experiencing now, which is the front wheel(s) disengage without notice when using the 4WD. I also can't always engage the front wheel(s) when shifting into 4WD. Also, do the front wheels have a limited slip diffential? It seems that just the passenger side is working, I haven't tried making it slip to see if the driver side engages. The truck came with a plow when I bought it last year and I'd like to use it this year, but plowing with 2WD isn't going to get me too far. Still will need to deal with the speedo/odometer problem and the intermitent check engine light. (I did buy the truck with the speedo problem and the check engine light just came on recently. I checked the code once(forgot it though)but the Chilton's book didn't have that code listed. I'll recheck and do another Post.