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Old 05-23-2016, 06:30 PM   #1
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Clutch, RMS, or Engine Mount? Drivetrain shuddering occassionally

Hey guys

Just to recap I have a 99 5 speed boxster with 45k miles on it.

In some certain circumstances I have experienced some drivetrain shuddering when taking off in 1st gear or reverse. It gets most upset if I try to modulate the clutch quickly, for instance when I accelerate more quickly than a car in front of me and then push in the clutch again, partially or all the way. Never any of the upper gears.

This rarely/never happens when the car is cold. It seems to happen most when either a; there is more than usual load placed on the car (for example reversing up a hill) or b; when I've been engaging and disengaging the clutch frequently like in stop-and-go traffic. Last year I had a almost identically-feeling problem in my Mazda2 and that turned out to be one of the transmission mounts.

It doesn't happen consistently so I'm inclined to believe it's not a problem with the clutch itself. The car doesn't appear to leak oil (indie mechanic who PPI'd it said the RMS was fine) but the symptoms could be explained by oil leaking onto the clutch sporadically, especially when hot. But I would think it would happen more often if this was the case.

Anyone had any similar problems?

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Old 05-23-2016, 06:44 PM   #2
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Funny you should mention this. I bought my Box less than a month ago and it had a shudder under hard acceleration in 1st gear only, along with what seemed to be sketchy clutch engagement shifting into 2nd. I took it to the shop for the IMS bearing and RMS. I asked them to check out the clutch and anything else that might be AFU. Turned out that the clutch had 50% lining left, but the throw-out bearing was toast.

The shop replaced the clutch and throw-out bearing. Since the engine was a later replacement for the original, the IMS could not be upgraded without tearing the motor apart. So, no IMS job. Now, the car shifts perfectly. No shudder or 1st to 2nd weirdness. Of course, in your case it might be something entirely different.
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Old 05-23-2016, 07:55 PM   #3
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Quote:
Originally Posted by imon_2nd View Post
Funny you should mention this. I bought my Box less than a month ago and it had a shudder under hard acceleration in 1st gear only, along with what seemed to be sketchy clutch engagement shifting into 2nd. I took it to the shop for the IMS bearing and RMS. I asked them to check out the clutch and anything else that might be AFU. Turned out that the clutch had 50% lining left, but the throw-out bearing was toast.

The shop replaced the clutch and throw-out bearing. Since the engine was a later replacement for the original, the IMS could not be upgraded without tearing the motor apart. So, no IMS job. Now, the car shifts perfectly. No shudder or 1st to 2nd weirdness. Of course, in your case it might be something entirely different.
I had a pilot bearing and TOB go bad on my RX-7. I know exactly how that problem feels. This feels different. I also really doubt a TOB or PB would eat it at less than 50k miles.
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Old 05-24-2016, 09:29 PM   #4
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I have similar symptoms in my 2001 5-speed. I have described it as a "clutch chatter", "judder" or "shutter" on clutch engagement when getting the car going in 1st gear. (And as you mentioned, it's really much more noticeable sometimes than others. For me though, sometimes I've thought it was worst when cold and might improve sometimes when warmed up.)

Here's a thread I started about it:
http://986forum.com/forums/general-discussions/59749-clutch-chatter-cause-correction.html

I can't quite put my finger on what conditions make it happen, I've been lining up replacement parts for clutch (clutch disc, pressure plate, throw out bearing, release fork, and guide tube and small pieces), as well as a new dual-mass flywheel since these are all somewhat suspect, and my car has 110k+ miles with no known/verified clutch replacement. Since the clutch is not slipping and has never slipped, it's a bit on the back burner.

I will add as I went through the winter, I noticed when it was very cold out (especially down into the 40's-50's F ) there was a pretty loutish/noticeable squealing sound for a minute or so after the car was first started in the cold and would immediately go away when the clutch was pressed, and come back as soon as clutch pedal was released - Almost sounded like a squealing fan belt - which I believe based on how it came and went with the clutch pedal, I figure this was likely the throw out bearing being unhappy (perhaps not spinning very freely, and even perhaps spinning/skipping on the pressure plate splines).

As I recently went desqueaking and optimizing the pedals, I also noticed what sounded like a low squeak or groan sound coming when depressing/releasing the clutch pedal, seemingly to come from the pedal itself (and also can be felt as a small vibration through the clutch operating foot), is actually, when you have the engine switched off, clearly coming from underneath car, back at the transmission. So, I have multiple pieces of evidence pointing to something not working quite perfectly smooth with the clutch/throw out bearing.

Meanwhile, my wife complains the clutch pedal effort is too high, although I haven't had the car long enough to know if it's by design or fixable. But I'll throw that bit in there too. Sorry I don't have a necessarily definitive solution but hope this helps.

I will also add that although I've not messed with the transmission mounts, I did replace the front engine mount. The original was in bad shape, but it didn't fix or even seem to help the clutch judder/shutter problem - at all.
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Last edited by jakeru; 05-24-2016 at 09:42 PM.
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Old 05-24-2016, 09:59 PM   #5
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I'll be watching your thread.

For now I'm going to basically drive around the problem. It doesn't seem to be too serious. My clutch is also a little squeeky; I assumed it was probably the slave cylinder needing some attention. I'll update this thread if anything changes or gets worse.
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Old 05-25-2016, 03:44 AM   #6
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Front engine mount. They are a known failure that can cause these driveline clunks, bangs, judders, etc...

Here's my daughters front mount and how bad it was when she replaced the bushing. The center metal part was ripped right out.



New one pressed in.

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Old 05-25-2016, 09:00 AM   #7
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Engine mount would make sense. The car has low mileage so I don't think mechanical/steel parts would be worn yet. But rubber breaks down mainly in regards to time, and the car is 17 years old. I'm gonna see about inspecting the mount with my indie sometime soon.
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Old 05-25-2016, 09:44 AM   #8
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I have a similar clunk when the car is cold and after it warms up it is more like a low thunk.

I will be replacing the front engine mount shortly and will post the results

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