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Odd thump/knocking/rattly noise from rear end ... finally fixed!

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#1 · (Edited)
Updated: 3/12/24 ... Yeah! Resolved. See end of thread.

2022 SEL Premium 2.5T AWD - 19,000 miles

About a month ago I started hearing a new “thumping” noise, sounded like it was coming from the rear of the vehicle??

A quick web and forum search found other SC owners with the same noise, and dealers doing everything from replacing shocks to replacing differentials, with and without success :-(

Before I hand it over to a dealer I thought I’d do some sleuthing to see if I could isolate it. 🧐

Symptoms:
  • Not metallic or “plastic-y” sounding, kind of a “muffled knock/thump”
  • Only heard at slower speeds, 5 - 15ish mph. Above that couldn’t be heard as road/wind noise took over
  • Even the smallest bumps in the road initiated the noise
  • Nothing could be felt inside the vehicle (steering wheel or floorboard)
  • Seemingly random frequency … frustrating/odd!
  • Straight ahead or turning … no difference
  • 5mph or 15mph ... no change in severity
  • Diff lock engaged or not … no difference
  • Drive mode changed … no difference
  • Braking, no braking … no difference
  • Coasting in neutral or transmission engaged … no difference
  • Removed EVERYTHING from bed side compartments, bed trunk, underneath rear seat, console and glove box … no difference.
  • Removed spare tire AND tailgate (that tailgate is heavy!) … no difference.
  • While under the vehicle pushed around on the gas tank and various linkages … zero slop, super solid
Seriously ... 🤨 WTF! 🤨

I’ve been working on cars/bikes a long time and like to think I’m at least half-ass good at tracking stuff like this down … but I was stumped!

Then in a late night web search I totally stumbled across a post in a Hyundai Palisades forum … and bingo! There it was … very likely cause and solution!

Turns out some Palisade models use the same self-leveling rear shocks as our SC’s. The upper shock “isolator mounts” wore out very quickly or were defective from the factory. Enough of problem that a TSB was issued for replacement on Palisades.

I would bet you a year’s worth of coffee /donuts the cause of my particular noise is exactly those isolator mounts, it makes sense now.

TSB is attached
From the TSB ... may exhibit a knocking or rattling noise from the rear of the vehicle when driving on bumpy roads at low speeds"


If you’re having this problem I highly recommend taking the TSB with you to the dealer. I might also recommend you cheat a bit and tell the dealer you did all my troubleshooting steps … even if you didn’t … wink-wink.

** Note that a special tool is required (but of course)***
I would verify before turning your SC over to the dealer that they have the special tool! I could just see a dealer taking the vehicle in, taking the shocks off, then discovering they don’t have the special tool to complete the replacement. Then putting it all back together, calling you, apologizing or making some excuse, then you having to do it all over again after they have the special tool in hand.

On the other hand, how likely is it that any dealer would do such a thing? /S

Regards
Ken
 

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#3 ·
2022 SEL Premium 2.5T AWD - 19,000 miles

About a month ago I started hearing a new “thumping” noise, sounded like it was coming from the rear of the vehicle??

A quick web and forum search found other SC owners with the same noise, and dealers doing everything from replacing shocks to replacing differentials, with and without success :-(

Before I hand it over to a dealer I thought I’d do some sleuthing to see if I could isolate it. 🧐

Symptoms:
  • Not metallic or “plastic-y” sounding, kind of a “muffled knock/thump”
  • Only heard at slower speeds, 5 - 15ish mph. Above that couldn’t be heard as road/wind noise took over
  • Even the smallest bumps in the road initiated the noise
  • Nothing could be felt inside the vehicle (steering wheel or floorboard)
  • Seemingly random frequency … frustrating/odd!
  • Straight ahead or turning … no difference
  • 5mph or 15mph ... no change in severity
  • Diff lock engaged or not … no difference
  • Drive mode changed … no difference
  • Braking, no braking … no difference
  • Coasting in neutral or transmission engaged … no difference
  • Removed EVERYTHING from bed side compartments, bed trunk, underneath rear seat, console and glove box … no difference.
  • Removed spare tire AND tailgate (that tailgate is heavy!) … no difference.
  • While under the vehicle pushed around on the gas tank and various linkages … zero slop, super solid
Seriously ... 🤨 WTF! 🤨

I’ve been working on cars/bikes a long time and like to think I’m at least half-ass good at tracking stuff like this down … but I was stumped!

Then in a late night web search I totally stumbled across a post in a Hyundai Palisades forum … and bingo! There it was … very likely cause and solution!

Turns out some Palisade models use the same self-leveling rear shocks as our SC’s. The upper shock “isolator mounts” wore out very quickly or were defective from the factory. Enough of problem that a TSB was issued for replacement on Palisades.

I would bet you a year’s worth of coffee /donuts the cause of my particular noise is exactly those isolator mounts, it makes sense now.

TSB is attached
From the TSB ... may exhibit a knocking or rattling noise from the rear of the vehicle when driving on bumpy roads at low speeds"


If you’re having this problem I highly recommend taking the TSB with you to the dealer. I might also recommend you cheat a bit and tell the dealer you did all my troubleshooting steps … even if you didn’t … wink-wink.

** Note that a special tool is required (but of course)***
I would verify before turning your SC over to the dealer that they have the special tool! I could just see a dealer taking the vehicle in, taking the shocks off, then discovering they don’t have the special tool to complete the replacement. Then putting it all back together, calling you, apologizing or making some excuse, then you having to do it all over again after they have the special tool in hand.

On the other hand, how likely is it that any dealer would do such a thing? /S

Regards
Ken
I have the same weird "thump" and have been under the vehicle several times trying to identify the noise. I felt like it was probably coming from the shock mounts and squirted some silicone up around there and it quietened down for a while but is coming back. Do you know if driving it causes any damage or just stays as an annoying bugaboo until addressed?
 
#4 ·
Long term with heavy loads in the bed, or towing, might eventually cause some damage. Other than that, I would say it's just annoying. On mine if outside air temperature goes above 75F the noise almost completely goes away! Below 50F its VERY noticeable. The shock itself is expanding/contracting and/or the rubber in the isolator mount becomes harder/softer with the temperature change. Been waiting for cooler weather to take my SC in so the tech can easily reproduce the problem.

Fortunately it's a simple fix and any dealer should be able to actually fix it correctly ... of course I have now just jinxed myself and my SC will come back with 8 new problems totally unrelated to why I took it in😂😥
 
#16 ·
Greetings, my 2022 Santa Cruz had the annoying thumping from the rear when it gets cold out. I finally took it in to the dealer. They replaced the rear shocks and upper mounts. The noise has not returned after a week. Best to do under warranty, these German built self leveling shocks are crazy expensive. If this problem returns, hopefully aftermarket shocks (non-self leveling will eventually be available). Good Luck!!
 
#9 · (Edited)
Well ...:(:cautious: and double :cautious::(

Got the car back from the dealer yesterday after they replaced both of upper shock isolator mounts, common cause of the problem on Palisades.

On the repair invoice it states "knocking noise no longer present". Wonderful!

Drive off their very smooth asphalt parking lot (no noise - yeah!) and a few blocks away pull into a more typically surfaced parking lot and .. CLUNK CLUNK CLUNKITY CLUNK. The NOISE STILL THERE and in fact LOUDER than before! WTF?

Geez ... I just drive home, keep listening to make sure I'm not dreaming all this up. Nope. CLUNK CLUNK CLUNKITY CLUNK at slow speeds (below 10mph ish) on tiny bumps/imperfections in the road surface.

Given the two dealers here couldn't even put the right weight oil in my Santa Cruz, I'm NOT keen on letting any of them "dig into it" further to find the cause.

Very odd problem indeed, moderately temperature dependent ... colder (below 40f) = louder and "harder", warmer(above 60f) = less loud and "softer". Sure seems like something that has rubber in it ... like the isolator mounts. Apparently not, unless the replacement mounts equally/more defective and that is entirely possible.

my next step (when the weather warms up) will be to remove both shocks and eliminate them from the equation.

You may ask ... "why would you go through all that trouble? That's what warranties and dealers are for!"

Cause I have a quite extensive history of dealer incompetence, I don't mind turning a wrench, removing shocks is easy-peasy and I know it will all be done properly without collateral damage.

Once I find the cause (hopefully) it'll be back to the dealer again. SUPER annoying but don't think any real damage is being done by continuing to drive it.
 
#17 ·
A little lazy in posting an update ... but here ya' go!

1st trip to dealer: "Yes there is a problem with your rear shocks". We both agreed to try replacing upper shock isolator mounts first. Parts ordered, waited 2 weeks.

2nd trip to dealer: Install upper isolator mounts ... did not fix the problem. ONE rear shock ordered and would be replaced. Yes only ONE. According to the dealer, Hyundai would not approve replacing both shocks at the same time, in case one of the two in the vehicle was actually "good". Even though the dealer had a tech ride in the bed and rattly noises could be heard from BOTH wheel wells. Hyundai would not approve both. Thanks Hyundai.

3rd trip to dealer: Install ONE shock. Test drive ... rattly noise still there. Order another shock, wait 2 weeks.

4th trip to dealer: Install other new shock. Test drive ... rattly noises gone! Yeah!

If the problem reoccurs I'm not going the "one shock at time" route again. Hopefully that won't be the case!
 
#18 ·
I strongly suspect your tail gate struts are weak. So when the car runs, the tailgate knocks with the body. After some time, as the struts heat, with the friction, the noise stops. Very irritating and something we would never suspect.
I suggest removing the tailgate struts, introduce foam to wedge the tailgate and body and check. If there is no rattling, the tailgate struts are the culprit.
 
#30 ·
i have a 2023 sel sc that I just got earlier this month and I hear the same noise. I definitely hear it when going slower. Hyundai in my town had it for a week before even test driving it, then test drove and heard the noise, but said they needed more time with the car. I said no and am taking it to a different dealership in the town over. Hopefully this will help get this resolved, thank you!
 
#31 ·
Mine turned out to be the spare tire wasn't fully tightened against the bed of the truck. Someone else found out that the shock absorber was causing a rattle; see TSB. file:///C:/Users/Owner/AppData/Local/Temp/MicrosoftEdgeDownloads/ec4f4d3b-a418-4d0b-938f-a748725c111c/TSB%20MC-10207814-0001.pdf
Odd thump/knocking/rattly noise from rear end ... finally fixed!
post #40