08-27-2012, 10:58 AM
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#1
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Registered User
Join Date: May 2012
Location: Sweden
Posts: 24
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Very scary knocking sound from back of the car
Just had the worst day ever, first some **************************** stabbed my plastic window with a knife (knife left inside of car) when parked outside work.
Then on my way home after a while i heard a knocking sound from the back of the car, sounded like it came from the right back wheel and the rythm followed the rotation of the wheel.
Driving slow - KNOCK.....KNOCK......KNOCK
Driving fast - KNOCKKNOCKKNOCKKNOCK
Since it sounded from the rotation of the wheel and not the engine RPM I felt like i could drive the last way home.
Had it in the garage a couple of hours and then was gonna show my dad the sound and it was silent. Drove around for a while to se if it sounded while being hot and sure soon enought it started.
Now to the scary part, found out that the the sound only exists if i have a gear in, if the car is moving in neutral there is no sound...
As soon i found out I turned it of and pushed it up the driveway.
Don't know if the information i gave here is good enougt, but what can it be that sounds only when in gear and when the car is hot? clutch, gearbox, IMS? flywheel?
Any idéa of how broke i will get fixing this?
Manual 986 from 1998
Last edited by tobiasr; 08-27-2012 at 11:43 AM.
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08-27-2012, 11:37 AM
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#2
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Registered User
Join Date: Apr 2012
Location: Riverside, CA
Posts: 1,665
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Is it a manual or automatic transmission?
What Year car?
From what I have been reading the Manual transmissions are fairly reliable and robust but the automatics may have had a bit of problems in some cases.
Automatic will be expensive and manual not quite so much usually.
Sorry for the bad luck.
Take the knife to the police station for finger print matching, file a police report on the damage sustained including that the transmission is now damaged and then see if your insurance covers transmission damage due to vandalism
With a bit of luck the vandal may have saved you the cost of repairing the transmission on your own dime since he broke in to your vehicle and did who knows what to damage the transmission.
__________________
"It broke because it wants to be Upgraded  "
2012 Porsche Performance Driving School - SanDiego region
2001 Boxster S, Top Speed muffler, (Fred's) Mini Morimotto Projectors, Tarret UDP,
Short Shifter, Touch Screen Dual Din Radio, 03 4 Bow glass Top (DD & Auto-X since May 17,2012)
Last edited by jb92563; 08-27-2012 at 11:40 AM.
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08-27-2012, 11:41 AM
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#3
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Registered User
Join Date: Aug 2011
Location: Malta
Posts: 144
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Can you check your transmission mounts? There's one on each side. Is car manual or tip?
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08-27-2012, 11:43 AM
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#4
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Registered User
Join Date: May 2012
Location: Sweden
Posts: 24
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Quote:
Originally Posted by jb92563
Is it a manual or automatic transmission?
What Year car?
From what I have been reading the Manual transmissions are fairly reliable and robust but the automatics may have had a bit of problems in some cases.
Automatic will be expensive and manual not quite so much usually.
Sorry for the bad luck.
Take the knife to the police station for finger print matching, file a police report on the damage sustained including that the transmission is now damaged and then see if your insurance covers transmission damage due to vandalism
With a bit of luck the vandal may have saved you the cost of repairing the transmission on your own dime since he broke in to your vehicle and did who knows what to damage the transmission.
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Manual 986 from 1998, think it will be hard getting a stabbed plastic window to cover any engine reparis since he never was in the car.
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08-27-2012, 11:49 AM
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#5
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Registered User
Join Date: Aug 2011
Location: Malta
Posts: 144
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Are you sure its from the wheel? A failing serpentine belt can be intermittent and causes a knocking noise as it will be slipping on and off the pulleys. I suggest you have a look at the belt. Generally it fails around 60k miles.
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08-27-2012, 11:58 AM
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#6
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Registered User
Join Date: Apr 2010
Location: Canada
Posts: 3,128
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i guess the hooker wasn't dead after all ...
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08-27-2012, 12:06 PM
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#7
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Registered User
Join Date: May 2012
Location: Sweden
Posts: 24
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Quote:
Originally Posted by rene525d
Are you sure its from the wheel? A failing serpentine belt can be intermittent and causes a knocking noise as it will be slipping on and off the pulleys. I suggest you have a look at the belt. Generally it fails around 60k miles.
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I dont think it was the wheel anymore since it only sounds when i have a gear engaged, changed serbetine belt a year ago and have gone 50k, will take a look on that! But does it make sense that is only sounds when hot and gear in?
Quote:
Originally Posted by The Radium King
i guess the hooker wasn't dead after all ...
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what? Oh now i get it
Last edited by tobiasr; 08-27-2012 at 12:10 PM.
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08-27-2012, 12:20 PM
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#8
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Ex Esso kid
Join Date: Dec 2005
Location: NY
Posts: 1,605
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Speed sensitive knock (one that increases frequency with vehicle velocity not a raise in engine revolutions) is likely rotational, in other words CV joint, wheel bearing, rotor pad, tire wheel.
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08-27-2012, 12:25 PM
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#10
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Registered User
Join Date: Aug 2011
Location: Neither here, nor there...
Posts: 458
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Quote:
Originally Posted by The Radium King
i guess the hooker wasn't dead after all ...
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 I doubt a hooker would fit, even in the front trunk. Well, maybe if it was a midget hooker. However, how about a trunk monkey?
Trunk Monkey Compilation - YouTube
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08-27-2012, 12:30 PM
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#11
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Registered User
Join Date: May 2012
Location: Sweden
Posts: 24
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Quote:
Originally Posted by tonycarreon
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Sounds like the first video, any idéa what that was?
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08-27-2012, 12:37 PM
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#12
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Registered User
Join Date: May 2009
Location: Frederick, MD
Posts: 1,396
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for me:
there is an e-brake cable on the driver's side that was ziptied down to the control arm. the ziptie broke allowing the wheel (which had the wheel weights on the inside of the wheel) to hit the line. everytime it came around i got a "fwapp". put a new ziptie and all was well.
get down on the ground and look.
there's also a clip you can get to negate the need of zip ties
http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=OEM-99965123002&catalog_description=Genuine%20Porsche%20Part%3A%20 CABLE%20HOLDER
__________________
"Speed has never killed anyone, suddenly becoming stationary... that's what gets you."
Last edited by tonycarreon; 08-27-2012 at 12:42 PM.
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08-27-2012, 12:49 PM
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#13
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Registered User
Join Date: Apr 2012
Location: Riverside, CA
Posts: 1,665
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Start checking the cheapest stuff first like the transmission mounts, rotors and CV/axle joints, or tire damage on the inside walls while your under there.
Once those are eliminated it will be much cleared whether its the transmission or not.
Transmission is not that likely unless somesone have been abusing it, but CV joints could be especially if the rubber boots have holes and letting abrasive material into that area.
Wheel bearings are another more common possibility.
Bar10dah: Love that Trunk Monkey, laughed for a good 5 minutes.
__________________
"It broke because it wants to be Upgraded  "
2012 Porsche Performance Driving School - SanDiego region
2001 Boxster S, Top Speed muffler, (Fred's) Mini Morimotto Projectors, Tarret UDP,
Short Shifter, Touch Screen Dual Din Radio, 03 4 Bow glass Top (DD & Auto-X since May 17,2012)
Last edited by jb92563; 08-27-2012 at 12:56 PM.
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08-27-2012, 03:22 PM
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#14
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Registered User
Join Date: Oct 2008
Location: Canyon Lake, Texas
Posts: 801
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I've got a bill staring at me on my desk for $7,600 to replace my Tip transmission ('00 base w/ Tip. 74k miles). Hope this isn't the situation you're in.
If you put it in gear up on jack stands (not that safe I know, but if done with car, can be done), have some put it into gear and check out the offending wheel more closely. Maybe take the wheel off and see if it still does it (again, on jack stands).
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08-28-2012, 07:06 PM
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#15
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Porsche "Purist"
Join Date: Aug 2003
Location: Wisconsin
Posts: 2,123
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Check the CV joints next.
__________________
1998 Boxster with 7.8 DME, 2005 3.6 liter/325 hp, Variocam Plus, 996 Instrument panel
2001 Boxster original owner. I installed used motor at 89k.
1987 924S. 2002 996TT. PST-2
Owned and repaired Porsches since 1974. Porsche: It's not driving, it's therapy.
Last edited by Paul; 08-28-2012 at 07:09 PM.
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09-20-2012, 12:18 PM
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#16
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Registered User
Join Date: May 2012
Location: Sweden
Posts: 24
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To follow this up, after a long time i finally got my mechanic to come out and check on it, he saw not visual damage on the CV joints or any other place, we started the car and drove around for a while.
Took about 20 minutes of driving for the sound to start, and he figured it only logical to be a cv joint, and the sound was when the joint was under load (engine breaking/acceleration), if having gear in but keeping speed it was silence, just as having no gear in (hope that you understand what i mean).
Will drive it to his workshop next week and he will take a better look and change what has to be changed.
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09-20-2012, 03:45 PM
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#17
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DIY extremist
Join Date: Jul 2011
Location: Brooklyn
Posts: 348
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Quote:
Originally Posted by stateofidleness
I've got a bill staring at me on my desk for $7,600 to replace my Tip transmission ('00 base w/ Tip. 74k miles). Hope this isn't the situation you're in.
If you put it in gear up on jack stands (not that safe I know, but if done with car, can be done), have some put it into gear and check out the offending wheel more closely. Maybe take the wheel off and see if it still does it (again, on jack stands).
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sounds like a lot for a trans... $2700 was my cost to rebuild on a 6 speed, are tips that much more?
__________________
"Betty" -- 2000 Boxster S, Triple Black, loaded except PSM (sold to a good home)
"Veronica" -- 2008 Boxster S, Arctic Silver on Blue
"Maleficent" -- 2007 Cayman S, Red and Black, TPC Turbo 3.6L 460 RWHP, H&R RSS Coilover / TPC stage 2 suspension
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09-20-2012, 03:53 PM
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#18
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Registered User
Join Date: Oct 2008
Location: Canyon Lake, Texas
Posts: 801
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It was about $4600 for the rebuild itself (a VERY thorough rebuild with new pump and everything), new coolant, labor, freight to ship transmission to CT, diagnostics, etc.
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10-05-2012, 05:32 AM
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#19
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Registered User
Join Date: May 2012
Location: Sweden
Posts: 24
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Update on the story, my mechanic just called me and told me he checked on it today, found nothing on the joints and drove for an hour without any sound this time.
Don't know what to do, since my gearbox first to second gear is often very hard to get in, maybe i should get it to some company with gearbox expertise and see if they know what it can be?
Going to go totally insane soon if this doesn't get fixed, hard to sleep well when something is wrong -_-
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