put my blazer in 4x4 on a dirt road yesterday and it started banging really loud (you could feel it) from the front left of the truck.. Whats the 1st thing I should check? I just had arm surgery and really don't want to pull more than I have to.

 

Banging could be coming from a lot of things. Is it banging in tune with the engine? or speed of the vehicle? If it's the later then it could be a cv shaft or posibly a wheel bearing.

 

I would check your Transfer case fluid levels, I had a similar bang and it was due to there being no transfer case fluid in there when I first bought the vehicle. you can almost feel it directly under your feet. Hope this helps.

 

yours was ok after adding fluid? Sounds like catastrophic damage was being done.. as soon as I got it back in 2x2 (took almost a minute) it was fine again.

 

Well it was running great( with the occasional slip when driving consistantly in 4wd) until I had an unfortunate misdiagnosis involving the transfer case, long story short YES. It did help. When you drain the transfer case fluid drain it into a clear pop bottle. Let it settle and look at how many metal shavings come out. This is a good way to see how much damage has been done. Hope it all works out for you.

 

wouldnt it still bang in 2x2 if it was one of those? I crawled under there and don't see anything wrong. how do you check the cv joints?

 

I am having the exact same problem with my '98. I'm pretty sure it's the drivers side CV shaft, because you can hear a slight clicking from the left side with the window down. And the banging changes with vehicle speed for me. Any other things to check before I tear into it this weekend would be helpful though.