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. :mad:


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

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.

Can you check your transmission mounts? There's one on each side. Is car manual or tip?

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.

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.

i guess the hooker wasn't dead after all ...

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?


what? Oh now i get it

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.

is it anything like what i experienced?

slow cruising:
constant noise 2 - YouTube

driving "at speed":
boxster constant noise from brakes - YouTube

:D 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

Sounds like the first video, any idéa what that was?

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.

http://986forum.com/forums/uploads01...1346099830.jpg

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%20CABLE%20HOLDER

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.

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).

Check the CV joints next.

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.

sounds like a lot for a trans... $2700 was my cost to rebuild on a 6 speed, are tips that much more?

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.

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 -_-