Things that go clunk, thump, etc

[fixer34]

What are some things that cause random clunks/thumps while driving? This is my daughter's 2002 TB 4WD LTZ. I've been trying to figure out a way to reproduce the noises 'on demand', but there seems to be no pattern. On a smooth, straight road, you might hear something once or twice over the course of a mile, then nothing. Bumps seem to make it happen more often, but not always. So far, the following have been replaced (because they needed to be, not for the noise issue).

Both front lower control arms-entire assembly with lower ball joint
Both front axle shafts. One sound is almost like a CV joint click, but..
One front axle hub (other one was still in good shape)
front and rear sway bar links. The sway bar mounts themselves seem good.
driveshaft U-joints seem tight-can shift from R to D and back with no 'clunk'
Nothing loose/rolling around on the rear storage compartments.
Nothing obviously loose underneath that I can see.

 

[The_Roadie]

Welcome! Have you wiggled the tires while in the air at their 9 and 3 o'clock positions to look for loose tie rod ends?

Might also be broken shocks or especially suspect is the upper shock mount. The rubber can deteriorate and tear.

How many miles? Any other maintenance history?

How often has the transfer case fluid been changed? Every 50K I hope! Differentials? 100K.

A strange cause of squeaks, which you don't have but you shold look anyway, is the threaded hood bump stops at the two front corners. You might unscrew each one a tiny bit to tighten up the hood.

Loose things like a battery hold-down under the hood?

 

[IllogicTC]

Differentials? 100K.

The owner's manual tries saying it's a lifetime fluid. It's not. Unless, I suppose, they expected these things to crap out by/before 100K, a possibility considering there's manufacturers with ads acting like hitting 6 digits is monumental these days when just 20-30 years ago they were building cars that are still around today with 4 times that mileage.

 

[Wooluf1952]

Welcome

In case you haven't heard:
http://gmtnation.com/forums/topic/218-welcome-to-gmtnationcom-heres-the-story/

I know you said the sway-bar end links were changed, but have you checked them? Other members have had problems with the nuts getting loose.

 

[fixer34]

Thanks all. I'll start from the bottom. Yes, I saw the Trailvoy -> GMTNation article. Exploring both at the moment.

I'll check the sway links again, but they were Moog units and just replaced 2 months ago.

We bought the car used about 2 years ago with 127k miles, it has around 135k now. Bought it from small used card dealer-looks like they gave a once-over before selling, but no idea on fluid changes. No history before that. Is the front differential separate from the trans/transfer case, or all handled by the trans fluid?
I'm probably going to get a chance to check the rear differential rear soon. The rear brake backing plates are pretty much rusted away and need replacement. I believe I need to pull the rear axles (meaning opening the differential case) to do this? Any tricks/advise welcome.

I knew there was something else I replaced on the front end-tie rod ends, so that should be covered. Everything else up front seemed tight. I'll give the rear shock mounts a close look. I assume if the shocks were broken, I would notice it with the 'bounce on the bumper' test?

Battery just replaced and locked down, so i think we're good there. Front hood also seems tight.

Nice day today, guess i'll get out and start crawling around.

Thanks all.

 

[fixer34]

OK, I think I solved one noise (but my daughter says there is still a bump/thump coming from somewhere near the front of the car). While crawling under to check the transfer case, I see this large black plastic canister in front of the fuel tank. It appears it is supposed to be held in place with a triangular bracket, but I could not get it to snap in. Instead it was resting on a metal 'shelf'. I'm thinking this is the source for at least some of the thumps. I removed the bracket and it appears to be warped slightly. Looks like I may need a new one to lock the canister in place.
I also noticed the plastic strap for the fuel filter was broken. A couple zip ties will fix that??