Macster

Noticed this a while back but just now getting around to commenting on it.

The transmission rattle is gone.

I'm speaking of the irregular "rattle" noise the car manifested when everything up to temperature and noticeable when sitting at a stop light and which goes away when I depress the clutch pedal and only comes back if while still stopped I give the engine some throttle then let the engine return to idle.

What did I do to get rid of it?

Not sure. I'm not sure when it went away. Working backwards at around 145K miles I had the coils/plugs changed. The plugs were not due -- had about 10K miles left -- and the old coils didn't look bad but afterwards the engine ran noticeably better. I would like to believe this is what smoothed out the engine and eliminated the transmssion rattle.

Let me add that I have had the plugs changed several times prior to this time and the engine never perked up afterwards so I attribute the improvement to the new coils.

Even further back at around 132K miles I had all 4 O2 sensors replaced. (One sensor was tripping a P0135 error and because they were all original I just decided to have them all replaced.)

Afterwards and kind of a surprise to me the engine ran better. The improvement wasn't quite as much as the improvement from the coils and plugs service but the improvement was real.

Anyhow, I'm pleased the noise is gone. And the fact the noise is gone suggests the rattle is not *normal* but a sign of a Turbo engine in need of a "tune up", a freshening of the engine consumables, like plugs, coils, and even O2 sensors.

dprantl

How long has the rattle been absent now?

Dan

Kevinmacd

Sounds like something in the clutch flywheel setup. Could be the throwout bearing!

Carlo_Carrera

+1

mffarrell

+2

Macster

Not sure when it went away. I heard it shorlty after I bought the car in June of 2009 and confirmed it was transmssion rattle for the noise went away when I depressed the clutch pedal then released it. I found I could bring the noise back by just revving the engine a bit then letting it return to idle speed.

The noise has been present off and on ever since and I just kind of ignored it.

A heat wave or two back though it occurred to me I wasn't hearing the noise and it used to appear in hot weather. It was more likely to appear in hot weather when the transmission oil was hot. And then I got to thinking about this and realized it has been some time -- a couple of years -- since I last heard the noise.

A lot -- relatively speaking -- has been done to the car over the last couple years. New O2 sensors in January 2015. New coils (and plugs) sometime last year.

Anyhow, the noise is gone, has been gone a while.

dprantl

Interesting. My car does it too, but only when it is very hot outside. Noise goes away immediately when the clutch is depressed. I'm having a hard time trying to understand why coils/plugs would make the noise go away. I was always thinking it was either a clutch component as others have already mentioned, or something in the transmission. Did you by chance also have the transmission fluid replaced?

Dan

Macster

No the noise was around too long to be a real mechanical problem. Also, I've heard transmission rattle from other cars I've owned. The Boxster even manifests this noise once in a great while.

The Turbo transmission was out at around 120K miles (for an RMS leak) and the clutch hardware was just fine. The tech, as is his habit, replaced the needle bearings that support the clutch control shaft, but he's done that all times the transmission has been out and the noise was present before and after.

993GT

it's gear rattle, normal...and is amplified by LWF/Cup cables, mounts, etc...

Kevinmacd

Still believe its in the clutch system or dual mass flywheel. Preloading the clutch when depressing the pedal and unloads the transmission, the noise goes away shows its in the clutch area or flywheel. If the release bearing hangs or the pivot of the release fork, or the release fork is worn, its possible the release bearing is not fully pulling back away from the pressure plate.

wice.lt

I have had this noise ever since I had replaced my gearbox mounts. With the summer's heat it became even louder. Have all the components to do a clutch job, but nothing is slipping so have just been living with it. Definitely gets louder when everything is up to the temps and weather is warm. Also notice that I need to depress the clutch before coming to a complete stop because the noise while coasting gets bad, but can be sort of reset with the clutch.

autobonrun

I'm used to the noise because I have LWF on both my 993 and 996. Definitely louder in the summer. I think the reason is that your AC Is on during the summer. AC load makes it louder. Turn AC off for a moment with it in neutral and you'll hear the rattle decrease. In winter no AC load means less chatter.

powdrhound

All totally normal. Depending on tolerances in the gearbox, oils viscosity, idle speed, flywheel mass, etc, etc, it may be audible more or less. Interestingly, after my engine and gearbox were built, any audible rattle disappeared. I attribute it to the fact that the engine is balanced better and has less vibration and smoother idle with its lightweight 3.8 pistons/liners, lighter rods, lighter RSR crank, and a slightly higher idle. The gearbox is also fully built and likely has tighter tolerances. While my car does not have A/C, it does have an 11lb LWFW along with Cup cables and semisolid engine mounts, pretty much the perfect storm for a lot of rattle. Even with these parts, there is zero audible rattle even with the gearbox in neutral with clutch out and fully hot 230F gear oil. I also don't have any of the annoying "marbles in a can" IMS rattle that was lightly present prior to the rebuild even though the engine now has 50+ track hours on it. Go figure..

Kevinmacd

No RMS rattle thats great! Was the RMS shaft and gears used in the GT3 used in your rebuild?

s65e90

Curious if you run a fluid dampr? I don't trust removing the dual mass flywheel without some sort of dampening unit.