OK, I have a 03 Blazer 4DR 4X4. I am hearing like a thump or a thud noise every time I hit a bump. Coming from just in front of like the passenger seat. So I brought it into the shop (I'm a technician) and shook down the front end thinking it was maybe a ball joint or stab link. I found that the LF lower ball joint was bad replaced it and I also looked at the stab links and they look brand new no cracks in the bushings or anything. Test drove it still heard the same damned noise and its driving me crazy.

P.S. I couldn't find any TSB's on Mitchell so I'm hoping someone on here has had a similar issue and could point me in the right direction.

 

Ok you're a tech so the suspension shake down should be cut n dry.
A sorta common issue are the conical washers for the hood. To test this theory you put a small rag that's folded a bit under the side (close to the hinge, on top of the weather stripping) you think the sound is coming from.
Been there, seen it, done it! If the noise goes away then you know it's the washers for the hood hinge/s. Simple & free & on my ride I was looking behind the glove box & wrapping chit up before I heard about this.
Odd sound as it sounds to be coming from the interior because the hinges are under the cowl & resonate in the cab - it throws you.

 

Yea that's exactly where it sounds like its coming from I was thinking about ripping out the dash... Guess I won't have to. So any ideas on some permanent fixes?

 

Getting the conical hinge washers & replacing them.
Not sure on the part # but a GM dealership should be able to get them for you.

 

https://blazerforum.com/forum/tech-articles-diy-29/hood-hinge-rattle-tsb-01-08-63-001b-38445/
That should help you.