The blizzard here in CO has required the use of the 4wd quite a bit the last couple of days on my 2001 Blazer LT (automatic transfer case, auto 4wd). Started noticing a clicking/clunking coming from what sounds like the front propeller shaft. Kinda sounds like a screwdriver being tapped against the propeller shaft.The clickfrequency isproportional to thetire speed, and at around 5 mph, the clicks are every second or so. The noise seems to disappear/diminsh if the drive train is loaded up or the speed gets above ~30 mph, and it is the worst while coasting/idling along. Reminds me of the clicking in a locking differential going through a turn, but this noise occurs while moving straight or turning in 4wd or Auto 4wd. It disappears altogether in 2wd once the transfer case has disengaged.

The joint on the transfer case side has some movement if I wobble the shaft by hand, so I'm guessing it's close toif not already shot. The dealer replaced the whole shaft a couple of years ago under warranty when the truck was in the shop for something completely unrelated. I can't remember what it was in for, but I know I was surprised to see the work order showing the shaft replacement. After they replaced it, there was a ton of grease flung from what appeared to be the joint near the transfer case, so I probably should have taken it back for them to explain what that was all about.

Is this a common problem? Sorry if this has been addressed multiple times, a forum search returned nothing similar. If it is common, does someone make something that will last more than a few years of occassional use?

Thanks for your help.

 

I have an 04 Blazer and had the clicking noise at low speed from below the driver's seat area.I also had grease flung all over the undercarriage in front of the transfer case. It turned out to be the CV joint at the rear of the front drive shaft. The dealer replaced the drive shaft assembly under warranty and the problem is gone.

 

I'd pop the shaft off and check it because it is easier to tell unless you've got the vehicle up in the air where you can see it really good. Four bolts on the front differential end and then it just slides out. I pulled one out because it felt bad under the vehicle but when I got it out it was OK. Once you've got it out it's obvious if it's bad or not. I had one sent out and had the CV jont cut off and a new one welded on for about half the price of a new shaft. I'd take a look at the seal also since you say there is grease all over.
I've done a few of these and what you describe is typical of what I've seen when they go bad. Last time though it turned out to be the front differential instead of the shaft but it also had a bit of a roaring noise in 4WD which also dissapeared in 2WD. That was a fun job !

 

Well today the clicking is back. The new shaft has only been in a few months. I thinking that there is either a problem with these CV joints or I have a misalignment in the drive line that is creating an angle greater that the CV joint is designed to handle. it's loudest when going over bumps or cornering. I'll be going back to the dealers.

Update - Turned out to be ball joints and idler arm this time not the front driveshaft CV joint. It was making a very similar popping / clicking sound. The lower left ball joint was shot and the upper left was loose. The dealer said that as long as they were replacing the lower they woud only charge for the part to do the upper(no additonal labor). The idler arm also would not pass state inspection and was replaced. They also did a four wheel alignment. Total cost including chassis lube, emission testing and disposing of old parts (now an enviromental hazardous waste disposal fee because of the grease) was $575.