Clunk and jerk

On my 1/2 hour drive home tonight, at least a dozen times, I experienced a single loud clunk accompanied by the whole truck jerking.

Despite the number of times it happened, I was unable to determine where the sound was coming from. It only seemed to happen at freeway speeds, but that may have just been coincidence. I thought I saw the tachometer dip during one incident, but am not 100% sure if it was my imagination or not.

Checked the transmission fluid, u-joints, and rear diff fluid when I got home; all fine. I figure it has to be somewhere in the drivetrain but am at a loss as to where to start looking, other than the transmission of unknown age and condition which was put in a year ago, and some leaking CV boots. Just thought someone here might recognize the symptom to help me narrow it down.

I have a 2001 Blazer with 4 wheel disc brakes and I had a parking brack shoe come loose, you have to pull the rear rotors to check. this sounds close to what I was hearing on mine.

Bob

Thanks Bob, I never would have considered that, I will check them out.

Mine seems to be doing the same thing it got real bad today i was hearing a clunk at times and would also seem to lose power but not during aceleration when i rev the moter up in park i thought that i might of been hearing the sounds of a cadalytic converter breakdown so i got under it and kicked it it does sound kinda chunky in ther but not sure cause today was the first time it has gone beond just a little jerk now and then i could use some advice to help pinpoint this problem

Mine did turn out to be a parking brake shoe, it was loosing chunks and getting caught up in the drum.