I have a 2000 blazer that started clicking in the front. Had a bad cv boot on right side, suspected cv bad so I replaced cv axle. Test driving after cv change discovered the clicking still there and also discovered in stops when 4wd hi is engaged. Any thoughts where to start?

 

Hmmm...Sounds like your CV axle was NOT replaced,only cleaned up and the shop ripped you. But it may be possible that if it was replaced it may defective(especially it was a rebuilt unit) The reason it may stop clicking when engaged in 4 wd is due to the additional torque applied to those axles...Just a thought

 

Sounds to me like the vacuum switch on the transfer case is stuck, allowing a slight vacuum to be applied to the front axle actuator under the battery: Dorman Products - 600-500 depending on where you go, it's under $20 and takes less than 15 minutes to replace it.

Driver side, next to the front driveshaft yoke, it has 3 vacuum lines attached to it. Pull the switch out and make sure the spring loaded ball moves in and out freely.