Clutch Fork Too Large - G50

[JohnJL]

I am having a problem getting resolution to an issue with my G50 transmission and clutch to play nice together. While the vendor has been responsive, he hasnt been able to resolve it. Frustratingly, he keeps repeating "I've done hundreds of these and never seen this problem before."

This is an 1987-89 shortened G50
PP is ZF
TO bearing is Sachs

I have verified with the vendor the correct order of the TO bearing installation and have left out one of the shims as instructed.

The problem is the "fingers" on the clutch fork are too thick to fit behind the TO bearing "ears." They are about 2mm too thick.

Here's a pic:





The fingers are about 16mm thick. You can see a manufacturing stamp of 05/94. The vendor has only been able to verify forks that date and newer and confirms they are all the same dimensions.

Does anyone have any ideas? Were the earlier G50 fork fingers narrower? Or is there a TO bearing that extends farther out from the pressure plate?

Thanks all

[88-diamondblue]

Which clutch disc are you using? Rubber centered or turbo spring centered.
Was the flywheel resurfaced? Also correct pressure plate for the 87-89 cars is Porsche part number is 950-116-023-03
89 was the first year of the 964, your vendor didn't get you one for it, did they.

I am grasping at straws here. I looked at the pictures and mine looked to have plenty of room to put the fork in. At least a bump to the top

[JohnJL]

Thanks Michael,

I'll say its all from Patrick Motorsports if that helps. James and Gary have been good so I dont mean anything in a bad way, just maybe that helps with parts issues or others' experience.

I'm not sure of the pressure plate manufacturer. It is marked with cast numbers on the circumferance. I dont have it with me, its at the shop. It was spec'd by James as the appropriate unit for my power/application specs. This is a race car with ~450 hp.

The clutch is organic and I believe a ZF. It has 4 springs, 2 yellow and 2 red. I dont recall if its 1 or 2 plates.

The bearing is a Sachs.

The fork has part number 950-116-712-3R. That comes up on Pelican as a fork for a 930 years 1976-1988. here it is...http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=930-116-712-02-OEM&catalog_description=Throw%2DOut%20Bearing%20Clutch %20Release%20Fork%2C%20%39%31%31%20Turbo%20%28%31% 39%37%36%2D%38%38%29%20

The crank is a 3.0 SC 1983 9-bolt

The transmission is a G50 shortened bellhousing from Patrick.

Thanks all

[john walker's workshop]

looks like you have the cupped spring upside down and it's touching the fork.

[KTL]

That's not a release fork from a 930 with a 930 trans. That fork is clearly a G50-only fork.

The earlier forks (the ones that use the old, problematic cross shaft with the bearings in the fork) do indeed have smaller release bearing fingers. The fork was later updated (not coincident with, but actually after the cross-shaft update) to beef up the release bearing fingers. The clutch housing remained the same even though the fork was revised.

I'm going totally by memory here, but I don't recall my clutch being so shallow. Can you shoot some additional pics of the clutch housing? I have a Kennedy Engineered Products (KEP) clutch that looks similar to yours. Do you see the KEP logo on it somewhere? I know for certain my clutch has the KEP lettering on it. I guess it doesn't really matter since the issue is the clearance between the clutch spring fingers and the release bearing.

Therefore, are you sure you have the correct release bearing? There are a number of release bearings that will fit in a G50 clutch housing. For instance I know for certain that we used a 968 release bearing with a 993 RS guide tube when we did a 3.6 transplant into a '88 G50 Carrera. We used a 964 RS clutch and an odd arrangement of various Porsche parts to assemble a clutch that worked. Since the 964RS clutch assembly was not as "tall", I suspect the 968 and 993 RS guide tube were needed to extend the release bearing further out from the clutch so the fork would fall into the right location when engine and trans are joined. Remember that the trans itself determines the placement of the fork to the release bearing, since the fork is mounted between the bores in the trans bellhousing.

[JohnJL]

Thanks Kevin and John.


John, I suspected you were right but we flipped it with the same result. James Patrick confirmed there should be no difference.

Kevin, I suspect you may be right. However Patrick has offered no answers and no sugestions. The only consistent response has been "we've been doing these for 15 years and we've never had a problem." Not that helpful.

I've repeatedly called and sometimes I get James and sometimes not. He doesnt return calls and emails only once.

I really appreciate both of your responses and any other suggestions out there. After $12,000 spent for what was supposed to be a no-mods fit-right-in-there solution I am losing patience. In the end it required significant torsion tube cut/mods and now the clutch wont go together. I specifically bought the shortened G50 from Patrick to avoid torsion tube mods but that clearly wasnt the case. Now the clutch wont go together and the service is ...I am becoming disgruntled...

[KTL]

John,

I'll dig up my early G50 release fork with the thin fingers. I looked thru my spares the other day and didn't find it, so i'll have to go in the basement to see what i've got. I'm pretty sure i've got one of these early forks I can shoot a picture of. The old fingers are much narrower depth-wise that the fork you've got pictured. I'll be honest that I don't recall my "later" fork with the beefier fingers being THAT beefy. I could be wrong- not the first time and not the last!

[CBRacerX]

I have an '87 G50 and updated the fork and flywheel/PP to 3.8 RSR style. Here is what the fork looks like:

[dean]

Originally Posted by KTL

I have a Kennedy Engineered Products (KEP) clutch that looks similar to yours. Do you see the KEP logo on it somewhere? I know for certain my clutch has the KEP lettering on it.

KEP makes the PP for Patrick.

I think you have the wrong TO bearing for the conversion. Call KEP they are very helpful. KEP gave me some info that I needed before I bought anything from them.

I can't remember what TO bearing I have.

[JohnJL]

I'll try that Dean. Do you have a link for KEP? My sorry search skills cant find it.

Thanks also Chris.

Do either of you have a measurement on the width (contact surface to back) of the thickness of the fork fingers?

cheers

[stevemfr]

http://www.kennedyeng.com/

[jevvy]

Cant help with the specifics of the problem but I can say that both the early fork and late fork fit on the later release bearing although I had a problem in the area after re-using an old version fork on a new release bearing:



My pic also shows must longer lugs on the release bearing compared to yours.

FWIW this is an RS clutch setup fitted to a G50 and 3.6 conversion.

[KTL]

John,

I searched and searched and cannot find my old clutch fork. I may have given it to cstreit to use for mocking up his clutch/trans. for his G50 conversion on his '70 S racecar. Let me know if you would still like to see this old fork and I will press him for a picture of it.

Sorry for the delay........

[alniki]

Here are some pictures of the original pre-updated releasing fork and TO bearing from my '87 3.2, engine recently dropped for swap.

[KTL]

The fork I was looking for is exactly what alniki posted. Thanks for posting the images!

[JohnJL]

Just to close this off (kind of.)

I ended up having to linish off about .75mm off the back of the clutch fork to get it to clear the pressure plate.

Have also found the clutch engages very high. I havent decided if this is good/bad/indifferent/a problem yet but it is quite tricky to drive.

[KTL]

G50 clutch engages near the end of the pedal travel- it's normal and kinda sucks, I know. You'll get used to it.