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Discussion Starter · #1 ·
Looking for some suggestions and guidance from my fellow SS peers as I am quite stumped.

Quick story...This spring at about 42k miles/5 years the car developed a rattle on the passenger side. Common wisdom says it's the swaybar endlinks. Before I address them, I send the car to the dealer to do the p/s rack recall. Everything done to satisfaction, receipt notes proper bolts replaced, car re-aligned, etc. Feels fine, still has the rattle. Order and install the Whiteline endlinks. Still rattles. Ok, next up in the common source is the strut mounts. Order Super Pros. Read up and review install procedure, nothing too complex and I've got all the tools - actually our front end is a bit simpler than a 4th gen Fbody's, which I've done a few too many times. Surprisingly, the pass side mount looks reasonable, although the driver's had a nice tear in the rubber for the full circumference of the middle metal piece so clearly was getting near the end of it's life already (thanks GM). I install the Super Pro's, cupped washer facing down as instructed. Now again having the experience of doing front suspensions, before taking the strut apart I marked EVERYTHING with a white painted line - springs, rubber seats, top isolator, all in line with the lower notch on the strut to ensure proper clocking when I put the strut back together. Bolt it all back in, and hey, the rattle is still there although less pronounced. Pulled the top cover dish back off with the car now sitting on the suspension, and find the nut on the top of the strut needs to be re-tightened AFTER you lower the car (later saw this referenced elsewhere), since compressing the suspension changes the height and relieves the pressure on that nut, ok no biggie. Sigh, slight rattle still there, mostly only heard at low speed such as moving in a parking lot, very faint. Disconnected the endlinks just to rule out them and the sway bar, no change. Double checked every suspension bolt, particularly those touched during the rack recall, and all are good and tight. At least the suspension feels much more solid with the new mounts, definitely less rattling overall, even over most potholes and depressions. Drive it for a couple weeks mostly around down and smooth roads, and the car feels great.

Until I discover that if I hit even a small raised bump in the road at highway speeds, talking an inch or two from road buckling, the car sounds like it's just nailing the bump stops - both sides are doing it. Pull everything apart again - double check and clocked as it should be "w" notch facing the engine bay. I can find nothing that would be hitting causing such a harsh sound (even disconnected the swaybar again). I gently pull down the ribbed boot covering the strut piston, and I don't even really see a visible bump stop on these magna ride shocks except right at the bottom of the shock body. There is zero chance I am compressing them enough to hit that over a 2" pavement bump. I can even go over a road depression and have the car rise and sink like normal, and it doesn't bang like that. Only when the suspension is compressing first.

So I'm at a loss. Hopefully someone here has a little wisdom or something to try. Searching here, and the related platforms G8s, VFs, GTOs, even Camaro5 etc I can't find anyone with a magnaride having the same issue (of course most of those platforms have traditional shocks outside the ZL1). The non-magnetic struts do appear to have a traditional bump stop on the piston, which I believe is why Super Pro instructs the cup washer to face down, to have a larger surface area for when contacting the bump stop.
 

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Discussion Starter · #2 ·
How bout this - can anyone who's done either the mounts or a spring/strut replacement on an mag ride car tell me if the fronts have a bump stop on the strut shaft? Started going nuts wondering if I tossed them in the trash with the stock mounts (which doesn't seem possible as I'd remember them), then reading at least one thread on here and a couple on Camaro 6 suggest the MRC cars don't use an external bump stop on the struts. Any vids online related to either the SS/VF cars are all non-MRC and they show bump stops, as does the GM Parts Direct images.
 

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Could the valving in the strut be messed up due to faulty/failing internals allowing them to compress way too much and bottoming out? Or conversely, failing to the other end of the spectrum and the valving be way too stiff not allowing them to compress when the suspension hits sudden hard bumps? I've done plenty of shock tuning for my offroad rigs and it sounds like a valving issue.

You can double check this by folding down the rubber boot covering the piston, then take a zip tie and tighten it around the shaft at the bottom of the strut. Then go for a drive and recreate the bump/noise condition. Go home, fold down the rubber boot and then see how far the zip tied moved on the shaft. If it's at the bottom of the shaft it tells you that your strut did indeed bottom out. if it didn't move at all, then valving is too stiff. If it's in the middle....got to keep looking for the problem.
 

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Discussion Starter · #4 ·
That's a great idea, thank you. I agree I think it's a valving issue in the second manner you mentioned, too stiff upon compression.

So I've ascertained the MRC front struts don't have external bump stops (so I wasn't nuts and didn't randomly toss parts), but there's an internal stop per a diagram I found on the FB group.

For reference:


I'll run the zip tie test to verify, but I'm still pretty sure it's not an issue of actually hitting the stop due to bottoming out or too much travel. I've seen it referenced on a couple other MRC platforms that an "electronic" stop can be programmed into the MRC logic, in essence putting the shock at full stiff to prevent it from hitting a mechanical stop. I'm theorizing maybe my ride height got borked up at some point and the car is thinking it's lower than it actually is, so upon compression MRC is going full stiff on me and hence the harshness over small bumps, yet no issues over some nasty potholed pavement or dips. After the zip tie test I may try to get a dealer to do a ride height reset/zero out and see if that helps. I did check the ride height sensors and arms, nothing seems bent out of the ordinary but I'm wondering if maybe I overextended the sensor and screwed up the calibration when the lower A-Arm dropped after removing the strut.
 

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Sounds like a good plan and your hypothesis sounds very feasible. Definitely keep us posted on this.
 

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Agree with the idea about zero'ing out the ride trim height. My suspension guy here in Dallas says he does it after any suspension work, even a simple alignment.
 
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