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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH996.2 Rear Creaking & High Speed Instability Over Bumps
Reported or suspected cause
right rear eccentric nut
Reported cause
No successful repair reported for this finding.
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Reported cause · Original poster
It turned out that the the right rear eccentric nut that adjusts camber had worked itself loose.
996.2 Rear Creaking & High Speed Instability Over Bumps
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Leading evidence: 'right rear eccentric nut' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'right rear eccentric nut' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Replace since the engine mounts' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
- Since the engine mounts were replaced because they were worn out, the transmission mount is likely worn too.
996.2 Rear Creaking & High Speed Instability Over Bumps
Tighten regularly
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Performed · outcome unconfirmed · Original poster
So everybody, make sure you have yours checked and tightened regularly.
996.2 Rear Creaking & High Speed Instability Over Bumps
original transmission mount
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996.2 Rear Creaking & High Speed Instability Over Bumps
Replace toe
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Suggestion · Original poster
Perhaps the transmission is moving around and causing the rear suspension geometry to change the toe under load?
996.2 Rear Creaking & High Speed Instability Over Bumps
Set )
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Suggestion
By the description of "stepping out" over high speed bumps, it sounds like the coil overs are just not adjusted properly (either too much/too fast rebound or too hard on the compression setting).
996.2 Rear Creaking & High Speed Instability Over Bumps
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9 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Hi All,
Looking for feedback on my diagnosis.
THE CAR:
- 2002 996.2 Tiptronic Cabriolet.
- High miles chassis, but documented engine rebuild 50K miles ago.
- Just took over the car so not sure of suspension history.
- New dampers front & rear. New engine mounts (I had them done can confirm this)
- Suspect original transmission mount. Haven't checked to see condition of them.
- Recent full alignment with corner balancing done by reputable race shop.
- Visual Inspection shows that front bushings appear to be in good condition.
- Front & rear wheels are the wrong offset, but no rubbing. Will likely add wheel spacers to compensate for this in the future.
THE PROBLEM(S):
- Creaking noise coming from the rear underside over driveway humps only audible at low speeds.
- At highway speeds over bumps, dips or major changes of pavement, the rear feels like it "steps out" momentarily.
- Steering wheel goes off center after going over bumps.
MY DIAGNOSIS:
- Since the engine mounts were replaced because they were worn out, the transmission mount is likely worn too.
- The creaking noise is likely coming from the worn transmission mount.
- The rear stepping out at high speed is also caused by the transmission moving around over bumps.
- Steering wheel going off center stumps me. Perhaps the transmission is moving around and causing the rear suspension geometry to change the toe under load? Or perhaps the steering rack bushings are worn (even though they look fine visually)? Or perhaps the cross member holding the transmission mount needs to be tightened?
PS: Has anybody had experience on Tiptronic mount replacement on the 996.2? Any advice? Thanks.
So, you don't mention what type of shocks/struts you have, but I'll assume they're coil overs as you do mention "corner balancing"... By the description of "stepping out" over high speed bumps, it sounds like the coil overs are just not adjusted properly (either too much/too fast rebound or too hard on the compression setting). It would be helpful to list the type of coil-overs you're running and whether they are two way, three way or only adjustable for height... Steering wheel "going off center" is called bump steer and it's caused by the change in geometry to the tie rod ends due to lowering... Can't comment on tiptronic, but I can venture a wild guess that tightening or loosening the trans mount isn't going to fix your problem. Yes, old rubber bushings & worn suspension parts are a real thing and can cause all sorts of funny noises, creaks, squeaks, clunks etc. I find it perplexing that if a shop installed your new coil overs, they didn't/wouldn't mention any of these other things though...
" rear end steps out.....steering wheel goes off center " STOP DRIVING THE CAR !!! Take it back to the shop. Sounds like someone left an adjustment point loose in the rear to me and one of the rear tires are just pointing where they want to after hitting bumps.
Rear end instability to the extent you’re talking about sounds like the toe is moving around.
The steering wheel off center could be because you’re toe has gone so whacked out... that would be special for it to be so far out.
Post the setup sheet from your corner balance, you should have got it from the shop and it will have every measurement...
I don’t know much about the tips but strut mounts are always something to look at when your suspension is creaking, along with the drip links.
Thanks all for the tips. Problem has been resolved. It turned out that the the right rear eccentric nut that adjusts camber had worked itself loose. So over bumps and uneven pavement, the right rear wheel would essentially flop around, causing all kinds of erratic handling. I was told by my alignment guy that this design is problematic and was used in the 996, 997, and Boxsters. He was clear to state that mine was the first time that he'd seen one actually get this loose. So everybody, make sure you have yours checked and tightened regularly.
@Porschetech3
You totally nailed it! That's exactly what happened. Brought it back to the alignment shop and discovered that the bolt clamping the eccentric washer either worked itself loose or the alignment shop didn't torque it enough. The wheel was flopping around and pointing wherever it wanted to go. They re-aligned, retorqued it. Been a week of driving it daily and so far the problem has not returned. Fingers crossed. Thank you.
