How do I fit a Turbo flywheel, Ruf pressure plate and Porsche ring gear?

[Dennis Kalma]

Getting slowly moving on the fitting of my 6 speed G50 to my '89 chassis. Just for background, the transmission is a G50/20, which will have the bell housing trimmed back a la those who fit G50 5 speeds to pre-87 911's. That, coupled with trimming off the big mounting boss at the nose of teh 6 speed, using up some of the space that was in the '89 chassis and perhaps moving the engine back a centimetre or so ought to make it work.

Anyway, problem at hand. I acquired a Sachs pressure plate, which after a long search was found out to be a Ruf part (Sachs number 88 3082 594), this part being aluminum and made for the Yellow Bird 5 speed. Allegedly it fits a Turbo flywheel (80 vintage) and takes a 240 mm Turbo 3.0 or 3.3 clutch disc.

Well, I got a Turbo flywheel (thanks Dave!), Turbo ring gear, lightweight starter and all and tried to fit it all together.

Well, we have a problem. As can be seen in the photo, the Ruf pressure plate is slightly (say 1/8 inch or so), smaller in diameter than the outer lip of the Turbo flywheel. The bolts all line up and it appears that the disc will be properly positioned, but I am uncomfortable that the pressure plate will move around without a lip to snugly hold it in place. Does anyone know whether a Turbo pressure plate is SUPPOSED to fit like that, or does the stock pressure plate fit snugly in the lip?



Second thing, the ring gear. I thought it bolted on the face of the pressure plate, using the same bolts that hold the pressure plate to the flywheel. No luck, a Turbo ring gear (930 116 230 02) is slightly smaller ID than the OD of the place on the pressure plate that it would logically fit. Question..where does the ring gear fit on a 3.0 or 3.3 Turbo flywheel/PP combination? Anyone got a picture of the set up?

Lastly, I have a new Carrera flywheel (930 102 033 03) and its cup is slightly smaller ID than the OD of the pressure plate...as per picture...



So that doesn't work either!

Help? I promise to keep at this till I have the only 6 speed '89 in the world, and of course keep all of you in the loop...

Dennis

[KTL]

The first issue I would not be concerned about. Other clutches i've done have simply sat onto the flywheel with nothing but little dowels to guide the alignment. The screws are doing the clamping force, and they're not typically mega high strength screws- only 8.8 property class. I'm no expert by any means though. I've only done 5 clutch jobs (three Porsche, one Mitsu., one GM). Also, the 930 flywheel has no lip on it to contain whatever clutch housing is native to the flywheel. So that native housing is also aligned via the mounting screws, no?

The second issue can be resolved by having a machinist cut the OD of the clutch housing to fit the ring gear onto it. I'd cut the clutch housing simply because it's got more meat on it than the ring gear. And the housing is softer alloy, no? Easier to cut. Does the ring gear have all of the appropriate holes to accept the rivets that are around the new clutch housing?

The third issue, i'd have a machinist cut the ID of the Carrera flywheel to fit the OD of the clutch housing. In this case, it seems better to cut the flywheel because it's surface does not have the obstructions like the clutch housing has. The housing has the notches in it and you could potentially be cutting against the spring assembly and whatnot that is around the OD of the clutch housing. I have a spare 87-89 G50 flywheel if you want it for testing purposes. It's used, of course. Cutting the flywheel ID on the backside of the toothed perimeter is not a big deal since the teeth are only for the DME sensor. Nothing actually engages these teeth to crank on the motor, so there wouldn't be any worry of that area being less strong from the cutting.

That's just what I think could be done. Some expert will probably come along and say the stuff I recommended will blow up your car and kill you?

Give a heads up to Souk on this topic. He went through quite an ordeal to fit a 930 short bell trans onto a '84 3.2 I recall he had to really get creative with the clutch assembly.

[dean]

My 930 pressure plate fits tight into the lip on the flywheel. I personally wouldn't run that Ruf like that.

I would give KEP a call. They have some experience with G50 conversions.

Dean

[carmad]

The ring gear on my pressure plate is an interference fit, I had to change it due to damaged teeth. A couple of blows with a soft hammer is enough to get it on and off. I also had to drill three new holes on the ring gear to accomodate some rivets when the pressure plate moves.
The inside edge of the ring gear is slightly bevelled, this should be the side mated to the pressure plate.
Hope this helps.
Call Stephen at Imagine Auto he has helped me on several occasions.