I have a Chevrolet Blazer 1989 with 5.7L Automatic 4WD Pickup.

Question: It has the TH700-R4 and standard transfer case NP241C. I have started hearing a clicking sound when driving. Same sound as if a small stone is pressed into the tire. The sound is not loud. Slow speed and window down and it can just be heard. Having the transmission in 'Neutral' and 2H and raised the vehicle in the back. I can hear the clicking sound, when I rotate (forward or backward) the tires. The clicking sound is coming from the transfer case to my best judgment. Observing the rear drive-shaft when rotating the tire, I can hear the clicking sound two times, when the rear drive-shaft is turned 360 degrees. The transfer case is correct filled with lubricate to the lower level of the filler hole. Any idea to what is causing the problem?

Answer:  We would suggest that you mark the driveshaft ends with white marker, take the drive shaft off and check all of the universal joints. If they all checks good the rear output snap ring in the transfer case is prone to breaking, suggest you pull the 4 bolt extension housing off the rear of the transfer case and inspect.