G50 clutch component options

[cmcfaul]

Replacing the clutch on a 89 Carrera with G50 Trans.

New stock Sachs clutch should be fine. There are a bunch of options. Do I need any of these?

Pivot Shaft
Release Bearing
Clutch Shaft Bushing kit
Other?

Thanks for the advice,

Chris

PS Clutch is original, shifts fine, just old (wont hold a burnout)

[dtxscott]

It might be part of the Clutch Shaft Bushing kit point, but you should do the pivot shaft update. It converts the needle bearing to a brass bushing. Always good to do the release bearing while in there.

You still have the rubber centered clutch at 120k miles?

I went with the Sachs clutch and can't tell a difference in noise or performance. All good.

[cmcfaul]

Thanks Scott, Will add those to the clutch order. Adds $500 to the cost of the clutch.

Chris
89 Carrera

[dtxscott]

The clutch actuation is much smoother with the bushings.

[Jeff Alton]

Complete kit (PP, Disc and T/O bearing) Plan to replace the cross shaft, bearing and fork as well. It is rare if they do not have wear on them.....

Cheers

[tholyoak]

You should be replacing the flywheel as well.

Todd

[Jeff Alton]

^^^^ only replace if it can't be machined to a point where it stays in spec...

[tholyoak]

You aren't supposed to machine a G50 flywheel especially if you are using the original rubber centred disc.

[Jeff Alton]

People still use the original rubber centered disc?

[cmcfaul]

Don't think the Rubber disk is available. Mine, however, seems to be working fine at 120k mi's. Cant do a burnout and the peddle is a bit stiff so probably on borrowed time.

Chris
89 Carrera, G50

[Jeff Alton]

Yes, the rubber disc, thankfully, is not available. Plenty of these flywheels have been machined over the years with success, and will continue to be.

Cheers

[Henry Schmidt]

I also have two personal cars 87, 88 getting engine upgrades.
3.4 Targa (for the wife...lol) and a 3.9 back-dated 88 RS crone.
Clutch and flywheel recommendations for these as well.

[88911coupe]

I thought I'd read the "don't resurface" order was specific to the rubber centered clutch. If you don't use that then resurface is acceptable assuming it's done properly...which is probably true of any resurface job? Also, I think there is something about the resurface that requires a gradient or something. Hopefully someone more knowledgeable than me can chime in on that issue.

[Jeff Alton]

Henry,

The new replacement spring centered kits work well and can handle quite a bit of power. Otherwise, a Spec Stage 1 or 2 depending on your torque plans for the 3.9.

There are other options out there, but we don't have any experience with them....

[burgermeister]

As long as the flywheel surface looks decent, why machine it? I have 220K on my flywheel. I 'refaced' it once around 165K with a woodworking RO sander and a 120 grit disc just to break the glaze (it had a RMS leak). Heresy, I know ... but I never had any adverse consequences.

[cmcfaul]

Lots of options. Kind of confusing. I ordered the Sachs clutch, Release bearing with rings, shaft and bushing kit. All in about a grand. Pelican is out of them so finding one was challenging.

Do I need the guide tube?

Should I replace the main seal (no leaks now).

Also, I noticed some versions of the Sachs clutch have 4 springs and some have 6 springs. Any difference other than design?

Thanks

Chris
89 G50 Carrera

[burgermeister]

If the new TO bearing fits on your guide tube, I think it should be fine. If it doesn't, there perhaps was some updated part?

The shaft & bushing kit is not a big deal to fabricate (or have fabricated). Just turn a shaft from 41xx or some other decent steel, an M6 in the end for the little tab to hold it, and a couple of $3 oillite bronze bushings from McMaster. I think that's exactly what the kit is. McMaster even sells metric round in a variety of grades, so just the center would need necking down. Though it sounds like you found a kit.

[KTL]

Yes the flywheel "cannot be resurfaced" mention in the factory spec book is completely related to the height of the rubber damper. It's stated right there in the image



Regarding the clutch disc, years ago the trick fix was to use a '75-'77 930 disc which is 240mm and spring-centered, before the 930 also got the dreaded rubber center disc. Nowadays the spring center clutch disc is standard issue. Unfortunately Sachs clutches and discs aren't as high quality as they used to be. But I wouldn't worry about 4 springs vs. 6. I just recall in recent past a handful of years ago that guys noticed the Sachs clutch kits had 915 discs that magically got a smaller friction surface and the assembly of the clutch housing wasn't done right with some riveting. Unfortunately its a sign of the times. Things just aren't made as good as they used to be, which is really shameful.

Yes you'll want to replace the guide tube if your clutch is original because the new release bearing is a different diameter than the old one. Therefore the diameter of the guide tube is different as well. See this tech bulletin from many years ago.



The release fork shaft has been a question for as long as I can remember (i'm embarrased to say i've been on this forum since 2000....... ). An aftermarket solution was created with a custom made shaft and Oilite bronze bushings that was supposed to be the cat's azz and solve all the problems. Problem is, it turns out the dimensions of the shaft weren't always right and the bronze bushings didn't last. This thread linked below covered a lot of crap.....

http://forums.pelicanparts.com/porsche-911-technical-forum/217367-g50-cross-shaft-update.html

and here's the DIY solution that member hcoles created, just like burgermeister mentioned

http://forums.pelicanparts.com/porsche-911-technical-forum/526421-g50-fork-shaft-upgrade-test-results.html

So after years of seeing this saga go on, it seems that if you have a transmission that has already been updated to the later style (bellhousing bores drilled out to accept needle bearing cups) then you're better off getting replacement needle bearing cups from Porsche. Reason I say that is because the aftermarket bushing solution doesn't seem to perform well long term and let's not forget the 964 and 993 cars have used this same updated design and they don't appear to suffer from epidemic failures. The key is that the needle bearing cups must have high quality long lasting grease that doesn't thin or dry out and they have to be protected from contamination (which was the demise of the original needle bearings in the release fork) via the rubber lip seals.
Porsche originally specified Castrol Olista Longtime EP, for whatever that's worth.

http://forums.pelicanparts.com/porsche-911-technical-forum/908840-update-g50-clutch-fork.html


The challenge here is that needle bearings really aren't a proper application but they seem to survive as long as they stay clean. It's my understanding from people in the know who design bearings and use them, needle bearings typically like high rpm operation. This clutch release shaft is clearly not high RPM. Porsche also spec'd a needle bearing in the steering shaft above the steering rack and that sucker is a problem too- because it dries out. I've also seen over the years ZF used a needle bearing for the pinion gear inside our steering racks and that does OK. Helps that it's fairly well sealed and bathed in grease, as long as the grease withstands the test of time?

Which main seal are you considering replacing? If you mean the engine main seal, if it isn't showing any signs of leakage then just leave it be. The main shaft seal for the trans is worth replacing since they tend to be leakier than the crankshaft. I believe you may be forced to replace the guide tube anyway? That shaft seal is a bit of a pain to get out due to the slightly tight space inside the bellhousing. I took a claw-style seal remover and shortened the handle on it to fit in the bellhousing, allowing me to pry the seal out.



Take note that the phillips head screws on the guide tube are notorious for stripping. An impact screwdriver (strike it with a hammer and it slightly turns) helps here. Or you just drill out the countersunk heads to the release clamping force on the tube and the screws then easily come right out.

[cmcfaul]

Thanks Kevin,

I ended up buying the bushing kit, guide tube, seal behind the flywheel, Sachs clutch kit with 6 springs and release bearing kit (with rings). Wish someone would offer a kit with all this stuff included. Ordered online from three different places until I finally found a place that could get a clutch for the G50. Apparently they are hard to find right now.

I dont think I will need a flywheel. Seems to engage smoothly now. Will likely clean up / deglaze if there is nothing obviously wrong with it.

Assume I can reuse all bolts.

Thanks,

Chris
89 Carrera 3.2 G 50

[KTL]

No problem. Hopefully it helped and wasn't too late.

The clutch kits are typically just the disc, bearing and clutch housing. So the rest of the stuff is pick and choose what you need.

Yep if your clutch engages OK right now and your flywheel doesn't have any major grooving or hot spots, it should work just fine with the new disc. Definitely a good idea to clean up the flywheel surface so you get good material transfer between the new disc and the flywheel. It's really much like brakes where you want to get the pads bedded into the rotor. Best way to do that is ensure the old embedded disc friction material is mostly removed from the flywheel surface. I've had good results with using a "rotor hone" like this

Flex-Hone for Rotors, Hone Tools, Flex Hones

Does a nice job of scuffing the surface for a light freshening.

Edit: Yes you can reuse the clutch housing bolts and also the flywheel bolts. It's occasionally been rumored that the flywheel bolts are stretch bolts but they are not. As long as they come out clean (no boogered head tooling) and threads look good, they can be reused. The Inbus or Verbus brand flywheel bolts are very high quality. Also be sure to use a good 12 pt. "triple square" socket bit to remove them.