when i floor it from a stop on dry pavement in my blazer there is a loud clicking noise. i am wondering if it could be the u joints on the rear drive shaft. it has a np203 but i just had the front shaft rebuilt.
does this happen when your in 4 lock or just four, it might be u joints, it might be differentials, it might be the chain in the transfercase hitting the sides, it might be the differential in the transfer case, there are lots of possibilitys, one thing i would definetly do though is put in a part time 4 wheel drive kit, you wont regret it!
The mile marke kit is really good. Here is a review of it: http://www.coloradok5.com/milemarkerpt.shtml It is suppoed to eliminate the problem foun in other kits. The reason that there is clicking is most likely because you are in the lock position. this setting deos not allow the front to slip at all, and that is where the clicking is from, the front tires are spinning at a slightly differant speed. Thats why this only happens on dry pavement (theres alot of traction) does it make the noise in just 4 wheel? cause if it doesnt, its not your ujoints or chain or differentials etc.
Like i said in that post a couple of months ago if you build up the shift fork you will not have that problem mine would do it so bad it would jump out of 4 wheel. Just something to think about i can tell you how to do it if you have any questions just ask.
Pretty much, thats the only logical explanation. the mile marker kit in the article replaces the entire differential assembly unlike other kits. There are two versions of the kit, and id be willing to bet that you had the cheaper one. the good one is the only one to go with.