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YOUR RESEARCHIntermittent vibration after transmission mount replacement
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Check over everything
Performed · outcome unconfirmed
No successful repair reported for this finding.
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Performed · outcome unconfirmed · Original poster
I took it back to my mechanic and they checked over everything for about a week and couldn't figure out exactly what it was.
Intermittent vibration after transmission mount replacement
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Leading evidence: 'Check over everything' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check over everything' (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
They ruled out wheels/tires, disconnected drive shaft and ruled out front end, disconnected serpentine belt and ruled out belt/pulleys as well as some other stuff.
Intermittent vibration after transmission mount replacement
Replace angle of something exposing a problem
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Performed · outcome unconfirmed · Original poster
His best guess is that the new mount tightened everything up and changed the angle of something exposing a problem that's probably been there but has been hidden.
Intermittent vibration after transmission mount replacement
Replace motor mounts are oem
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
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Performed · outcome unconfirmed · Original poster
My motor mounts are OEM but they were replaced within the last year.
Intermittent vibration after transmission mount replacement
Replace oem trans mount
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Performed · outcome unconfirmed
Ever since I replaced my oem trans mount with a FF mount, I've had an intermittent vibration most noticeable at around 3k rpm.
Intermittent vibration after transmission mount replacement
Disconnect drive shaft and ruled out front end
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
They ruled out wheels/tires, disconnected drive shaft and ruled out front end, disconnected serpentine belt and ruled out belt/pulleys as well as some other stuff.
Intermittent vibration after transmission mount replacement
Replace angle of something exposing a problem
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
His best guess is that the new mount tightened everything up and changed the angle of something exposing a problem that's probably been there but has been hidden.
Intermittent vibration after transmission mount replacement
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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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Generation: 20261028T003752Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
So I had my transmission mount replaced in my '02 C4S Tiptronic with 136,000 miles and immediately afterward I noticed an intermittent vibration when in lower gears depending on the speed. For example, 3rd gear at 40ish mph = strong intermittent vibration, 4th gear at 60ish mph = strong intermittent vibration, etc. It is much more noticeable after the car has warmed up.
I took it back to my mechanic and they checked over everything for about a week and couldn't figure out exactly what it was. They ruled out wheels/tires, disconnected drive shaft and ruled out front end, disconnected serpentine belt and ruled out belt/pulleys as well as some other stuff. His best guess is that the new mount tightened everything up and changed the angle of something exposing a problem that's probably been there but has been hidden. (pardon my generalizations, I'm still a bit of a newb)
He said he's narrowed it down to either the rear differential or the transfer case. He said flushing fluids might help but he wasn't sure and said I should probably take it to a Porsche dealer to see if they can positively ID the problem.
Has anyone ever had this problem before or does anyone have an idea what the problem is/what I should do?
It's an oem mount like this one. Not necessarily at a specific RPM but it does seem to be more noticeable at higher RPMs. However it isn't consistent. Ex: I can be at 2500 RPM in 5th gear and it won't be noticeable. But at 2500 RPM in 3rd or 4th gear it's very noticeable.
The one pictured above looks to be a superceded 997 version which is solid vs. the semi-solid 996 mount as an fyi. Dunno if it's suppose to transmit any more NVH or not though.
Is your engine mounts original?
The pictured mount above is an aftermarket semi-solid mount. It's used on the 996.2 Carrera Tiptronic and GT/Turbo transmissions. (The Carrera manual transmissions use a pressed-in bushing for the trans mounting point).
You're correct that the 997 transmission mount superceded the 996 trans mount (which is no longer manufactured), but the OEM mount is NOT solid. The internal geometry was beefed up vs the 996, but it still has voids.
Oops I do have an aftermarket urethane mount. My bad. Still, that shouldn't be causing an intermittent vibration should it? A constant/consistent vibration increase would make more sense to me. My motor mounts are OEM but they were replaced within the last year.
Thanks for clarifying that. The pics I've seen at some angles made it look solid to me.
It also doesn't help that I'm looking at half these posts on my 4.5" mobile.
Ever since I replaced my oem trans mount with a FF mount, I've had an intermittent vibration most noticeable at around 3k rpm. Always while decelerating. Tap the throttle usually gets rid of it.
Pedro's garage website claims that's a normal vibration for these engines. FWIW
I know this is a couple years old.... But did you ever get the vibration diagnosed and fixed??? I have a C4S 997. About 3 months ago I changed my Transmission mount with oem Lemforder hoping it would tighten things up and make shifting more consistent. It did help with aggressive down shifting into 2nd gear where before every once in a while it would balk and not go into 2nd gear while making an aggressive downshift before a turn. What I did notice on drive home after swapping it is that only under full load acceleration in 4th or 5th gear at about 90mph + I starting to feel a low "rumble". Never felt this before until immediately after changing the transmission mount. Did you have any discoveries??
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