in my 2000 blazer 4x4
when backing out of a parking spot, or the drive way, in 2 wheel high, once i get up to about 5 mph i will hear a loud deep thump. it only does this when im backing out, and doesn't always do it. it did it only once going forward, and it was at least twice as loud. its only when im accelerating. and it seems to happen most when its been sitting for a few hours. it almost sounds like i hit a garbage can or something. the sound comes from the dash, but i know its under the hood. i think my dad had it checked out and it was something in the 4x4. we've had this happen for a few years now and it hasn't caused any trouble, 4x4 works fine, no lights in dash come on, so we never really payed much attention to it. i was just curious why it happens. the truck has approx. 106k miles. anyone have a similar problem?

 

no one has had a similar problem?

 

transmission mount broken? I had it happen on my camaro...

 

idk, i found out that it also happens just after i start the truck
i was letting it warm up in my driveway in drive with my foot on the brake, and it did it

 

does it sound like a loud klink in your rear end?

 

Does it do it in 4hi or 4lo? Could be a cv shaft with a piece of a cv joint broken. Possibly the front acctuator.

 

no the clank is in the front, its like a deep clank like i hit a garbage can
i dont think it does it in 4wd, i dont think ive ever had it in 4wd and reverse at the same time lol

 

Can you just hear this thump or can you also feel it? If so, does it feel like it is right under your feet or elsewhere?

 

im gonna go along with bandidolenny on this one, this seems like a suspension problem not a 4x4 problem. id crawl under the truck and check everything out (cv's, balljoints,the whole works) and if ur not sure wat to look for take it to a shop to have it inspected they shouldnt charge much at all just to look at it.