Clunk / multiple rebound from rear suspension, service center says it feels "normal"

[rogersmj]

So, while "they all do this" is likely accurate at some level, I think letting Rivian think it's anything other than unacceptable is a misstep. I've taken mine to 3 different service centers, none of which could resolve the issue, so I pursued a lemon buyback with Rivian, which ultimately resulted in me keeping the truck and getting a cash payout. Enough of us raise our voice in this manner it will get their attention eventually. They'll either fix it, or decide it's good enough and just payout those of us that complain loud enough (likely cheaper than resolving it).

I strongly suspect this is the route I'm going...that I'm just going to have to complain a lot but not much is actually going to change because it's a design defect.

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[Jonger1150]

You're not wrong. It's a first edition of a very unique suspension system. There isn't anything else on the market like it, which I think leads to some of the "Well, it's just this way" mentality.

The noise isn't the air springs. It's the half shafts and the active hydraulic dampers that make the noise.

I've had air suspension, both factory and aftermarket, for over the last decade and NONE of them rattled/clanked like this one. The Q7 had similar articulation (~5in compared to~7in on the Rivian), and I drove it well over 100k miles without noise. When it did start to rattle, it was a strut mount, not the strut itself. Had aftermarket air suspension on my Sierra, granted those airbags were separate from the dampers, the supported weight was similar.

I've also designed industrial machinery that has sliding splined shafts that don't rattle like these. Some transmitting 100's of HP with significantly more articulation, AND in a vibratory environment. Those were, arguably, "beefier" shafts, but it's the same premise. Articulating joint on each end, and a sliding splined shaft in the center. Service life for those was around a year, and they were designed to run 24/7/365 (60k hrs), which is equivalent to ~1.5mil miles (25mph assumed). With that said, they were custom built, and not high volume production pieces, so I get they aren't completely apples to apples there; but I think it's close enough for this conversation.

**edit** Found a video of the machine I designed that used those sliding connections. This is a "steady state" video. Startup and Shutdown had amplitudes in the 10-15in range depending on loading. Steady state amplitude was closer to an inch or so.​

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https://photos.app.goo.gl/Ghh9qiRXypUtxTbaA​

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**/edit**​

Personal opinion here, not backed by any measurements, just backed by decades as a mechanical engineering and self-proclaimed car guy status.......The half shafts have a poor manufacturing tolerance as well as poor design, and the electro-hydraulic suspension suffers from cavitation due to poorly sized lines/valves/fittings.

Better tolerances on the splined shafts would add cost, but eliminate the "rattle" that they have under reversing loads. Also, moving the splines from the moving bit to the stationary bit would also likely help that issue. Putting the splines on the output shaft of the drive units, and not in the middle of the shaft would eliminate a good portion of the loading it sees. It's a more difficult sealing arrangement to solve, but I doubt it would rattle.

--I THINK--The hydraulic dampers are "loud" due to the "water hammer" style effect of cavitation as fluid moves rapidly into/out of the cylinders under reversing loads. This particular effect is worsened by less than consistent air bleeding techniques by different service centers and the factory. Lines sizing, fitting radius considerations, and internal routings could likely lessen this effect.

So, while "they all do this" is likely accurate at some level, I think letting Rivian think it's anything other than unacceptable is a misstep. I've taken mine to 3 different service centers, none of which could resolve the issue, so I pursued a lemon buyback with Rivian, which ultimately resulted in me keeping the truck and getting a cash payout. Enough of us raise our voice in this manner it will get their attention eventually. They'll either fix it, or decide it's good enough and just payout those of us that complain loud enough (likely cheaper than resolving it).

Funny enough, being in SE Michigan and in one of Rivian's main R&D locations I happened to see a job opening for an engineer who has extensive experience with half-shafts. Started at $140,000 and you would need to relocate to the Plymouth MI area. I'm being completely serious.

(I do not work for Rivian, I just saw the job posting)

 

[Jonger1150]

I strongly suspect this is the route I'm going...that I'm just going to have to complain a lot but not much is actually going to change because it's a design defect.

The R1T & R1S will never be the volume model for Rivian, but it will be the higher profit margin product. R&D work should continue and eventually a better half-shaft should come along. Let's hope they don't change the fitting with new models and maroon us with models that will never improve.

 

[2kwik4u]

Funny enough, being in SE Michigan and in one of Rivian's main R&D locations I happened to see a job opening for an engineer who has extensive experience with half-shafts. Started at $140,000 and you would need to relocate to the Plymouth MI area. I'm being completely serious.

(I do not work for Rivian, I just saw the job posting)

My engineering days are behind me, but appreciate you keeping a lookout. I moved into management a few years ago and am much happier here.

 

[rogersmj]

Funny enough, being in SE Michigan and in one of Rivian's main R&D locations I happened to see a job opening for an engineer who has extensive experience with half-shafts. Started at $140,000 and you would need to relocate to the Plymouth MI area. I'm being completely serious.

(I do not work for Rivian, I just saw the job posting)

My engineering days are behind me, but appreciate you keeping a lookout. I moved into management a few years ago and am much happier here.

 

[2kwik4u]

That.....well......that's something. Appreciate the support, but I'm not gods gift to engineers. Although I will admit I do like to think that from time to time.

I won't tell you I haven't had the thought of getting a job at Rivian just to "fix the bugs" and then quitting. Read a story years ago (might be ubran legend) of someone doing that at Facebook. Hated a particular bug so bad he got hired on, immediately fixed the bug, then quit.

Interestingly enough, my truck is going back into service tomorrow. The clunk has gotten signficantly worse after this weekends off roading trip, alignment is no longer correct, and there is a pronounced driveline "groan" at full throttle. I'm going to do everything this side of begging for a new subframe to try and quell these issues. We'll see what they come up with.

Now that the Fob is working reliably again, if they can fix the "clunkyness" of the suspension, then my only major gripe left will be the dumbass digital AC vents. That's one I think I could live with over time.

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