I think that I know what you are saying about the braking feeling. I noticed that on my Ford 250 also the other day when I was on bare pavement. I needed to use 4WD to get up a small hill on my yard when the grass was wet. When I pulled out onto the driveway and made a sharp turn, it felt like I had slammed on the brakes.

The Isuzu 4WD really should not be used on dry pavement.

Are all four of your tires the same size? I am struggling to find a solution for your issues that doesn't involve replacing the current hubs. One year at Moab, one of the rigs blew two tires one day. The owner bought two new tires in town that were a size larger as the owner was intending to go to the larger size. It was a disaster. The transfer case could not deal with the two ends of the vehicle running at different speeds.

BTW, the changeover from auto to manual hubs will probably take less time than it will take to try to service the current auto hubs.