How do I KNOW I need new shocks?

My '04 Tahoe LT has nearly 300k miles. Replaced the motor with an LQ9 6.0 and had the trans rebuilt just 2 years ago. Oh, wait... ok it's been 3y. But less than 15,000 miles, I think.

I put Bilstein 5100s on in late 2017 when I did a slight lift, probably 30k miles since then. No more than 40k, but whatever. The last 18 months I've started doing a little bit of towing a trailer, but sometimes with a decently heavy load on the trailer. Mostly hauling some wood for the smokers, once hauled 3 large propane tanks (2 250s and a 500) that were empty a few hundred miles. Not heavy-ass boats or anything.

Anyways, it seems a little sloppy, more sway the last year or two. A passenger commented on this and brought it (more) to my attention, he wondered if I had sway bar problems.

Moreso, though, I have lots of squeaking with any kind of bumps. I can't tell when driving if this is coming from front or rear, really. I can't seem to make it squeak from standing on the bumper and bouncing. The squeaking is with any small bumps on anything but the smoothest of roads. I do notice it 'tightens up' and goes away when braking coming down a hill. I don't know if this is because it puts more weight and tension on the front suspension or takes weight OFF the rear suspension. I thought this could have been a wheel bearing that a shop told me needed replaced (driver's front bearing), but after replacement of the wheel hub (Moog 515054) and inner/outer tie rods (Moog ES3488 & Moog ES3493T) in that position, it has remained and continued to worsen.

Most notably, when picking up a couple of ricks of wood a couple of weeks ago, the rear of the truck was REALLY squatted down badly. I was pretty tongue-loaded on the trailer, but it seemed to be a lot worse than I would have expected. Still had the squeaking when loaded and towing.

My question is, what am I looking for to evaluate my shocks from underneath? I can pull it into my friend's shop and get it on stands, but I'm not sure what I am looking for under there that might give me a clue? Worn bushings and that kind of thing ought to be pretty obvious, I'm sure - when I did the shocks in 2017 (again, 30-40k ago?) I did put in a Moog K80631 Stabilizer Bar Link Kit but didn't replace the stabilizer bar. At the same time I also put in Moog 81069 coil springs and did a slight key lift - like maybe 2-3"? So when I'm under there I'll inspect and look for cracking of bushings and things, but I just want to know how I can specifically tell if the shocks are shot, besides leaking fluid, of course. I don't mind replacing the shocks, I've watched some videos and this looks like a relatively easy job, but I hate to spend a couple hundred bucks right now and not end up fixing my problem. Things are extremely tight for us financially at the moment.

Tips?

I will add, when I replaced my original shocks back in 2017, I knew they were bad because when driving at highway speeds, I would feel the truck 'skitter' sideways a little bit when hitting bumps. Very unnerving, but I didn't have these weird squeakings, so I don't really know... I'm not feeling that jumpiness like I did back then, just very loose feeling and that squeaking noise. Is it possible this isn't my shocks? Something else, like the sway bar, could certainly make it feel unstable, but would that cause all this squeaking, too?

For shocks, jounce the suspension and see how much she moves. A stuck shock might not allow one side to move at all. Worn shocks will let her move quite a bit. Then there is the noise.

Aftermarket stuff doesn't last as long as GM OE.

Check sway bar bushings.

That really depends on who you ask. Shops that do suspension work basically say replace them regularly (like a certain miles, and I want to say I've seen as little as like 50k). 50k seems way too little to me for most everyday regular driving on paved roads, but again, shops make a living on replacing things like shocks, so no surprise really.

I've gone over 100k on factory shocks and replacing them basically did nothing, implying that the old ones weren't really worn.

Of course, driving conditions also play a factor too. Highway driving on smooth roads is very different than driving extended distances on like gravel roads. City driving on pothole-riddled roads I'm sure is not good either.

This has never happened to me on any of my vehicles, but I've seen driving vehicles on the road and the oscillation is pretty darn obvious (no damping at all!). It seems to me those people just don't care (they probably notice it)... basically the people that drive vehicles until the wheels fall off. I also believe the suspension is beefier on these trucks vs unibody vehicles.

Some have expressed concern about the steering, I think that's probably good. It's been checked several times, as this is always a concern with vehicles this age. Notably, one local shop tried to really almost force me to replace the Pittman arm, telling me it was unsafe and they could be liable if I drove it away without replacement - blah blah blah, we've all heard this story before. I took the truck to my own highly trusted mechanic at that time and he checked it and told me nothing was wrong, don't worry about it. The interesting thing... this was probably 200,000 miles ago. No kidding, I think it was in the first year I owned this truck, probably 2010, maybe 2011. And this shop was pushing me to replace a Pittman arm that is STILL in service today.

Needless to say, I don't go to that shop anymore.

I know the steering/front suspension has been checked at 2 shops in the last year(plus) - as I has first the recommendation to do so, and then actually replaced the left wheel hub and left inner/outer tie rod. I THINK it should be pretty much standard to give a once-over to all the components of the front suspension and steering when doing this, right? I dunno...

Now that I think about it, this DOES sound more like bushings of some kind. And the lack of instability when at highway speeds (like the 'skittering' I was previously experiencing) and my inability to duplicate problems by bouncing on the bumper... might point more to some kind of bushings - maybe the very body bushings I bought 4 or 5 years ago and then never installed? LOL I'll need to dig more into this... but the more I think about it, the more I am glad I didn't just buy the shocks and replace them willy-nilly.

I DO wonder about how badly my truck was 'squatting' when I was towing that trailer though... it hasn't ever been NEARLY that bad before, but maybe I was a lot more tongue-loaded than I thought.

It is easy enough to lube the sway bar bushings, and I suggest that you do this first and see if the squeaking goes away.

The more I look into this, the more suspicious I am of the body mounts than the shocks. Shocks were good quality Bilsteins and I would expect more than 30-40k out of them - and like I said, it doesn't feel like bad shocks felt prior to that replacement.

I know GM body mounts at this age (~20y) are probably going bad, it's a common thing. I also know there are 10 or 12 of them, rusty and hard to get to - I'm thinking I may just bite the bullet and have a shop do that. They'll be much more efficient at that particular job than I will.

I may take it out to the shop today and jack it up, crawl under and see if I can tell from looking, but those things (from the videos I've seen) appear to be in pretty tough spots and I may not be able to tell without actually removing them whether they need to be replaced - but after 20y and nearly 300k miles, I am pretty sure it wouldn't hurt anything to replace them.

Just... probably a $4-500 job, and $250-300 worth of parts. <sigh>

Jacked up the front end, looked undernesth. Body bushing surprisingly all look to be in good shape. Go figure.

Need all new bump stops, front and back, but that's not my problem.

Looks like I need 3 out of 4 ball joints, leaking or cracked. Might as well call it 4.

Need new passenger side inner and out tie rod. Inner is torn most of the way off, outer is leaking and cracked.

Control arm bushings all look to be good. Front stabilizer bar linkage all looks good. Stabilizer bar bushings look good and tight. Rear stabilizer bar one bushing looks a little loose, I could see a little gap in it, but they're not cracked. Stabilizer bar bushing problems usually cause clunking when hitting bumps, not squeaking, dont they?

Cant see that those things that need replacing should cause all this infernal squeaking and swaying though? Just front end loose or steering issues?

The front "bump" stops are not that, they're called "jounce" stops and should be contacting the lower control arms at ride height. Having them properly contact stabilizes the suspension to some degree.

Got a pic of yours?