License2Ill

iTrader: (1)

Chris u dont think something could effect holding up the body to some degree....between the panhard rod's location and i dont know maybe the sway bar as well??...they may cause interference from the body truly buckling down on the springs fully.
A quick answer would be i guess to pop out the springs and see if the body tries to hit the floor or is held up a little.
It could be like u say tho...maybe just exhuast hangers.....but in that case we would catch the rattle when we rev the engine in park.....and I dont get that at all....i get some rattling in the middle of a bump...or right after...or maybe pulling out of a steep driveway.

basically maybe the isolaters pickup an inch of space that secures them and makes them not rattle according to the length our stock springs. by removing them...the car doesnt totally always settle on to them for other reasons and u occasionally would produce a rattle.
If the car is truly compressing the spring without the isolater we shouldnt get a rattle there.

ChrisRZ28

If you take the springs out the car will rest on the bump stops. The springs are compressed by the weight of the car. The springs won't make noise fully weighted. I think the noise issue is somewhere else. As far as revving the engine and hearing noises, thats not enough movement to make noise. The exhaust system is heavy and you need to run over bumps to get the exhaust system to bounce or move. The only thing you would hear if you revved the engine would be a loose heat shield or if the exhaust is close enough to the floor a noise that way.

strokerrace

iTrader: (8)

Wow I guess this is a more common problem then I anticipated... Been busy and havnt checked the thread in a while just got done gettin my new trans and clutch put in. I did notice however that when i push up on the car from underneath it my rear sway bar mounts are squeaking but this is different from the clunk I normally hear over bumps. I wonder if it may be the bumpstops hitting the axle since im lowered? Hope somebody can find something...

ChrisRZ28

I'm leaning towards the exhaust being the culprit for some of the noise. I drove around again today and some of my noise has gone away after messing with the exhaust hangers. It takes bigger bumps now to make the same noise as before the 'fix'. Strokerrace, if you hit the bumpstops you'll feel it. I'm lowered also (26.5) and I don't think I've hit my stops yet. But I've also cut mine down some.

strokerrace

iTrader: (8)

I have the poly jeep bumpstops not cut down or anything. Not sure of my ride height cant remember...

License2Ill

iTrader: (1)

I'm with you Chris I stopped to look over the hanger hooks and the rubberized ears they slip into....there is definitely plenty of air between the hooks and the rubber.....so it would seem the whole muffler could shake up and down and cause a rattle.

Maybe lowering changes the body angle slightly enough to cause it to shake more than normal.

ChrisRZ28

It's the jarring ride from the stiffer suspensions that we put under our cars. Think about it. Soft suspension soaks up bumps, doesn't put any extra stress on heavy exhaust systems and things. Add a suspension that usually is stiffer plus less travel and the resulting harsher ride is going to add stress to the whole car and the exhaust.

License2Ill

iTrader: (1)

Makes a lot of sense...maybe we should wedge something in between the hooks and the rubber....more rubber im imagining..maybe underneath the hook....gravity and weight will probably wear it out tho sooner than original. I wonder how much slack it truly needs forward and backwards?? that could tell us if we could actually bend the hook so as to limit that as well.
There looks like there would be slack for left and right motion too. Thats XYZ axis.

Sucks becuz I cant get under the whole car right now to see the other points we could probably make tighter. Makes you want to forget the rubber and just pin it down....they should make those in poly...for sure the poly would come in handy for the heat and durability. If GM wanted some play back there it's gotta be for a reason. I wonder if a lighter muffler back there would make things better for pinning the hooks down instead of all this. Who would of thought all this chit for a short drop.

Im not lowered that much....i've got 1993 z28 springs in the back that have over 160k right now. They were definitely shorter in comparison to 95 units. Cant explain why but i did a side by side comparison and that was the visual. Then of course I took out the isolators and did hose mod. Upfront I clipped the springs about .35 of a full coil. So about an inch up front...and maybe 1-1.5 in the back. How much and how are you dropped?

ChrisRZ28

I've forgotten how much I've cut off. But my measurements are 26" for the front, 26.5 for the back. Measurement takin' from the ground to the top/center of the fender arch. I don't think it's a good idea to 'pin' the exhaust. It needs to move a little. The two hangers in the back are the only ones I added some small pieces of rubber to.

Swaie

iTrader: (6)

I thought you guys had the same sound that I have in my T/A, but I guess not cause there is no way that I would consider that sound being suspension. I think it is coming from my rearend...I don't know what it is yet but there is no way it is exhaust or could be isolated as being suspension. I drive down a 1/16th of a mile of driveway gravel and I hear it coming from my drivers side rear. And that was a very good asessment of the noise that I hear. I can with gravel in it...sounds just like that.

License2Ill

iTrader: (1)

hey man love the picture!!
i know what kind of noise you are talking about as well. before I ran these stock 93 rear springs...i had cut my original 95's by about half a loop.

I was definitely lower than I am now. And your sound was much much more prevalent then. I get this still but nowhere near as much.

We all are running a number on the what the car's engineers originally intended.....when WE chose to lower our vehicles. The gravel in a can noise is just that....the tires are picking up road debri (not cups and plastic and chit debri) little specs of concrete or in some cases true gravel...or rocks....the tires as they spin then begin to let them go and fly off it....it flies off and hits surrounding areas.(the cans)..the wheel wells. And so you get the noise you speak of more drastically the closer you are to the ground.

It's almost as if the engineers actually measured the average spin off flylength and made sure to keep our wheelwells right outside of this. So just a small variation or drop and we'll begin to hear it fly off and bounce off the "can" lining.

Maybe noise surpressor film can help..either that or unlower the vehicle(proposterous I know). Either way that particular noise should pose no danger.

Also try to make sure you put back the little shock pillows above inside the cabin behind the rear seats. Somehow if you dropped the shocks and forget to put them back in.....they surpress a LOT of noise.

jtut90

iTrader: (5)

I still have factory rear isolators just lowering coils, did it before and after the install of the lowering springs, my rear antenna is horribly loose tho I think that is my cause, I can literally take the antenna and spin it in a huge circle all the bolts somehow fell out, I will tighten it and let everyone know how it goes.

Wesmanw02

iTrader: (4)

Interesting thread, my car started making the same noise after I rebuilt the rear and installed a new differential!! Its a horrible noise each time you hit a bump with the rear of the car.

I think the issue may be at least somewhat attributed to the c-clip axles. Just the other say I took the rear apart and fixed the axle end play problem I had by using external snap rings in the c-clip grooves to take up the extra space, and then grinding down the center spacer to get the clearance just right. After doing that, the rear has been much quieter over bumps!! It no longer sounds like the axles are going to fall out when I go over roadroad tracks or speed bumps!!

RobRomero

iTrader: (1)

Sounds like this thread is getting a little off course. As mentioned before, the sound being investigated by the OP would sound more like a can of rocks than a suspension "squeak."

-Rob

LS_BlueBird

Seams like a pretty common problem... I’m chasing the same noise on my T/A, and it only seams to happen with medium to hard bumps. I think I’ve found it but with no solid solution to fix it yet, may help someone else here too. I'm lowered (26.5") also with a rebuild rear, aluminum diff cover, adjustable panhard, cut bump stops, stock cat-back with e-cutout. After some investigation, the first thing I noticed was the wire bracket attached to the diff cover for the e-brake cable was hitting the stamped steel panhard bracket so I moved it for lots of clearance. The second thing was the aluminum cover with the bearing cap bolts that stick out, the one stud on the right side makes contact with the same stamped steel bracket, I can clearly see an indentation in the steel. Mine got better as time went on too but it was just bending the bracket more and more.

metalmilitia606

iTrader: (8)

I just finished putting on new springs and shocks and adj lca's and panhard bar. I tightened everything down, but when I shake my car side to side it makes this horrible rattling thudding sound. Then if I go down a bumpy road the bumps break the lock nuts on my lca's loose so then it rattles even worse. Even when they are tight though something still rattles. I'm leaning toward the old 10 bolt about to take a dump. My seal is toast and the diff cover is covered in oil. I have also noticed that if my buddy rocks the car by the quarters I can feel the clunk through the tires. I really think something is dying inside the rear end.

License2Ill

iTrader: (1)

Here is the op's original post mr wanabe mod...what i dont understand is what did YOU add towards resolving his problem? or even sharing it in any kind of similarity?

Thread looks just fine and if ANY thread were to go off course then that means that no one could help but people got steered into talking about something ballpark or maybe nothing at all in common....but ur not a mod so what do u care?
#2 your post is actually the most removed from the subject entirely....everyone else shares some common ground with the op.
Your post is the most unwarranted and unsolicited. when u find yourself looking to post like this just ask urself if u have any common ground? can u input help or add to the same problem or similar? if ur answer is no and u want to just make some observation then remember thats NOT ur job. and go knit a sweater.

License2Ill

iTrader: (1)

Dude this is an incredibly helpful observation...and could very well be the root of the problem in more than 1 case. Are you also lowered? cuz lots who have the problem are lowered.
Great fix!! u think c clip elimanators could be used to also fix this slack space you found?

Wesmanw02

iTrader: (4)

Yep, I am lowered on Strano Springs with Bilstein Shocks.

C-clip eliminators would work, but as far as I know they do not make a street use c-clip eliminator kit for the GM 7.5. They only make the drag kit, which won't work for street use.

FormulaTA327

I just installed a panhard and lcas with poly/rod adj. end and they clunk when I hit small bumps and I dont know if anyone has experienced clunking when backing up almost like something metal is hitting back and forth on something. Wouldnt something with rod ends move a little and with that make that clunk sound, Im not experienced with aftermarket susp. so i dont know if this is normal. It seems after reading all this that rod ends susp. clunking is what it naturally does.