The G50 conversion and the strange noise

[Burint]

We've just finished the conversion G50/00 on to 930. 1986
These are parts that went in.

pedals, complete hydraulics, shifter & linkage assemblies.
The clutch & flywheel,* standard aluminum Turbo
pressure plate + release bearing + guide tube bolts
Sachs spring hub disc flywheel + bolts + pilot bearing
+ ring gear + Viton rear main seal
A aluminum clutch plate suitable for modified
Turbo engines over 400hp (ex: headers, muffler, turbo,
intercooler, 1bar boost).

The first gear is a little hard to engage but finally without forcing, it went in.
The turbo is pulling strong without any issue but I noticed some strange sound.
We came back to garage for checking.

Sorry for my writing, this is the best I can explain.

-When idle, I started hearing a strange friction, grinding sound (similar when the bearing in alternator gone bad) when step on clutch, the sound is gone.
-When shut off the engine, the noise is still heard for another split second.
-When runs at low rpm. in any gear. the noise is louder competing with the sound of the engine. When I step on clutch, the noise is gone.

Any comments is truly appreciated.

[nyne11]

? throw out bearing?

[dean]

That sounds like the normal sound from a G50, although it is hard to tell from here

When I first drove my conversion, I thought there was something wrong but now I don't even hear the sound anymore

[DW SD]

I AGREE: throw out bearing. Did you use a new one?

[Burint]

DW SD,

If it isn't on my part list on first post, I guess I am using the old one.

[Wavey]

I'd also guess a bad throwout bearing. Or incorrect clearance due to wrong combination of parts or incorrect adjustment, keeping the bearing in contact with the pressure plate when the pedal is not depressed.

[KTL]

Sounds like normal G50 bearing noise- that being internal gearshaft bearings, not clutch release bearing.

My car developed this sound after driving it hard on the track for a few years. My release bearing is new. Two friends with G50s (87 and 88) sound the same. I'd not worry about it. One guy's G50 has 160K on the clock, never opened up for service. Still drives it like he stole it, every time he drives it.

[Burint]

Hi guys,
I got the respond from Chris Caroll at Turbo Kraft and thought this might be useful. Thank you for all your help.
Burint

Chris wrote

Burint,
The G50s are a lot noisier than the 915s and 930s, but you’re probably familiar with that. They make noise when idling, or whenever the clutch is engaged.

Is there any pulsing through the pedal? Or if the car is up on a rack and running, see if there’s any pulsing and knocking feeling in the bell housing. That would tell me there is contact between the release fork and the pressure plate fingers. This is unusual, but I have had that happen on a 930 within the past year. We had to use a sanding wheel to remove about 2mm from the back of the fork right where it was touching the pressure plate.

Other things to check while in there:

1. Was the guide tube shortened? If I supplied it, I would like to say “yes”, 100% it was shortened. But it is possible I made a mistake and it wasn’t shortened by 2mm.

2. I had one other car were the disc hub made contact with the guide tube, so we took 2-2.5mm off that, too.

The only other thing is something internal to the gearbox, like bad bearings on the mainshaft that make noise when driven (clutch not pressed and released).

Let me know what you find.

[lite75]

Hi,
How much was the housing shortened? Is it hard to shift in all gears?