Ken964

So I am having some problems shifting and getting into gear.

here are he symptoms:

The pedal feels funny even after bleeding, it has more travel before resistance and it is softer.

I cannot shift into any gear with the engine running.

If I try to push the pedal further to the floor I hear a grinding sound, not unlike the shift fork engaging the ring gear.

The roll pin is still in operation.

The master and slave cylinder have been recently replaced and show no signs of leaking.

Are these symptoms of a broken or cracked shift fork? How could I tell without disconnecting the engine from the transmission?

Is it really possible change the fork out without dropping the engine?

thank you in advance

__________________
Ken

'89 C4 Coupe
'88 Mazda MX6

garrett376

I doubt it's the fork that broke, but more likely the bearings/bushings may have disintegrated that hold the fork together. How many miles on your clutch?

Colin 90 C2

You can see the fork when you remove the inspection cover. It's probably best to have the car on a lift.

JasonAndreas

Seized release bearing?
(although unlikely...)
Did you measure and adjust the clutch pedal travel after replacing these? It should be 145 +- 10mm but if there is too much movement the back of the release fork will come into contact with the starter ring gear (or for MY90+ the pressure plate) and make a grinding/clicking sound.






Your transmission will likely break before the release fork does so hopefully it doesn't look like this.









There is also an inspection port on the bottom of the transmission bellhousing meant for checking the amount of clutch disc wear but you should be able to look through it and check the front of the ring gear for score marks.


I wouldn't try it without a hydraulic lift.

Ken964

Thank you for the ideas, I will take a look in the inspection port and readjust the pedal travel. Hopefully I did not do too much damage.

The clutch has about 16k miles on it and the fork and associated hardware are also listed as being replaced by the PO's mechanic.

If the pedal was incorrectly adjusted so the release bearing was always engaged I guess that would explain the disintegrated bearing there.

I will keep everyone posted on any progress.

take care
__________________
Ken

'89 C4 Coupe
'88 Mazda MX6

jmreiser

What did you find out?

Ken964

It turns out my pressure plate was cracked:
https://rennlist.com/forums/964-forum/322497-cracked-pressure-plate.html

Everything came out without too much trouble, a stuck PDAS actuator and rounded out cheese heads were the worst.

The release bearing was still in good operating condition and spun nice and smoothly. The release fork was also fine and the bushings were operational although they required some pounding to remove the operating shaft.

Ken
____________
'89 C4 Coupe
'97 Volvo 960 Estate

And

Just saw Jason's pic of the broken transmission (pic from bell housing end)...
This is exactly what mine did - clutch fork pivot bearing seized, spun inside the transmission 'ears' and finally broke one...
My mechanic / me are having a tough time getting this sorted:
- can't source a replacement front trans casting
- can re-weld though don't have the dimensions to re-machine
- complete replacement trans seems a bit of a waste...

Any ideas?? Anyone have dimensions for re-machining the shift fork pivot??

Thanks much,
andrew

jmreiser

What our local welding shop guy did was pretty clever. He asked me for an old, junk release fork pivot axle. He put it in position, then just welded around it. Aluminum weld does not stick to steel. Then he justed pulled out the junk axle, and voila, we had a correctly sized hole. No machining. It works fine.

JasonAndreas

I bought a 19mm graphite EDM rod from McMaster-Carr to weld around but would have preferred Joel's solution. One of the aluminum bosses was pretty much missing completely and had to be built up from welding rod. So I don't know if the steel bearing cage would have warped with all the extra heat? At one time Porsche sold a 19mm boring tool (it's NLA but most dealerships and a few independents still have them -- see the TSB below) for align boring the pre-964 G50 bosses, the problem is that the alignment holder is around 13-16mm in diameter and your hole is 19mm. So it requires a little bit of extra work to use but it does work. And as long as you don't weld inside the bosses you shouldn't need the special Porsche tool. I wasn't comfortable leaving it with welds only around the outside so the extra welds on the inside required that I rebore the holes.

Here are some photos of the welding with a little dremel tool grinding but before the boring.









and here is the TSB from Porsche.