First you have to understand a little about the shift-on-the-fly mechanism used in the GV. It does not have automatic locking hubs, it uses drive flanges that are engaged 100% of the time which keeps the CV axles spinning all the time. The front diff has a vacuum actuator that slides the internals over about an inch to engage the axle shafts when 4wd is selected. When in 2h the axles are not engaged in the diff but they are still spinning. Also the passenger side axle seal has been known to wear over time, so constantly spinning makes it wear faster.
Pro's:
- less wear on CV's, boots and seals
- can disengage axle's if something breaks and need to limp home in 2wd
- some report better fuel mileage
Con's:
- must lock the hubs to use 4wd.
Note that if you leave the hubs locked it is essentially the same as the drive flanges that are already on the GV so you can safely lock the hubs all weekend if you plan on using 4wd, or even all winter if you frequently encounter slippery road conditions.
Another benefit of using manual locking hubs is that you can swap out the 3rd member to remove the shift-on-the-fly since people have been known to have problems with the vacuum actuator coming off and loosing 4wd all together.
Take a look at this article for more info on the GV's shift-on-the-fly mechanism
http://www.zukiworld.com/month_030104/feature_tsb_shiftontheflyremoval.htm
