Clutch/Transmission Issue- Any Ideas?

[Bravoaloha]

Hey Guys,

I have been sorting my car for two and a half years now. ('86 911 with a 3.6 and Shortnose G50) Every time I think I get her in a good spot something else goes wrong.

Took her for a ~3 hour round trip last night. No problem getting there. I drive the car hard but carefully. Mostly highway driving- about 20 minutes from home there is a toll booth, 1/3 of a mile to a big long really fun sweeping lefthand causeway. (Parkway North to 78 West for any Jersey folk out there)

I left the tollbooth in second and accelerated hard through the gears. I am pretty sure I only made it into 4th (but I could have shifted into 5th I don't remember.) When I downshifted into third the transmission crunched and would not go into gear. It was a clean shift, I did not miss a shift or anything. From there I put it in fourth with no issue.

As I shifted around something definitely felt off. The clutch pedal had a lot of vibration and though the transmission felt ok, it definitely didn't feel right.

I did not have to stop the rest of the ride until a light by my house and another stop sign. At those stops it felt like the clutch wasn't fully engaging and the car would buck as I was releasing the clutch.

Any ideas?

[yelcab1]

First, inspect the slave cylinder and bleed it. If that does not help, pull the engine out, inspect the pressure plate. It may be time for a new clutch, pressure plate, flywheel resurface, TO bearing, and shift fork update.

[Bravoaloha]

Thanks Yelcab. Is there anything else I can do between inspecting and bleeding the slave and pulling the motor? Definitely trying to stay away from a project that big!

[yelcab1]

Well, when it comes to clutch and related stuff, it's all in the gearbox and the engine comes out for that. You can do some preliminary diagnose without taking the engine out.

1. Inspect the slave cylinder like I said
2. Shift with the engine off, does it go in all gears? If no, there are shifting problem outside the box. If it refuses to go into a gear (3rd) then the problem is inside the box
3. What does it feel like with the engine off when you press down on the clutch? Is there even pressure all the way down to the bottom? If not, the pressure plate is cracked
4. Do your engine and tranny mounts look good?

those are the only things you can do from outside the box. The rest, engine out time.

[Bravoaloha]

Thanks again Yelacab

She shifts around fine with the engine off (all gears). Clutch feels normal too. Engine mounts are new, tranny mounts I have to assume could use replacing.

Just loaded her on the trailer.. about to read up on bleeding the slave and heading down to my shop from there to give that a go!

[aston@ultrasw.c]

Which pressure plate and release bearing did you use?

For the 3.6/shortened G50 combo, many companies sold a 930 pressure plate with a g50 bearing.

Well, the bearing retainer does not engage on the PP fingers very securely and it could come loose causing all kinds of weird bollocks.

Patrick Motorsports now sells a custom pressure plate. Like all things PMS, it costs a fortune, but it works. Can't argue with that.

[Bravoaloha]

Originally Posted by aston@ultrasw.c

Which pressure plate and release bearing did you use?

For the 3.6/shortened G50 combo, many companies sold a 930 pressure plate with a g50 bearing.

Well, the bearing retainer does not engage on the PP fingers very securely and it could come loose causing all kinds of weird bollocks.

Patrick Motorsports now sells a custom pressure plate. Like all things PMS, it costs a fortune, but it works. Can't argue with that.

The swap was done by a PO but the listing said the following "G50-01 Light flywheel with clutch kit stage 2 from Patrick Motorsport" so I'm hoping I am in the clear on that.

Tried bleeding the slave today and now I have a soft clutch to add insult to injury.

[wayner]

I have a 915 transmission in an earlier car so I am not sure if this applies, but our symptoms were the same.

In my case it was a cracked clutch fork inside the bell housing of the transmission.
Any clutch pressure just flexed the fork and it twisted each time instead of the fork actuating the clutch

[Bravoaloha]

That would make sense Wayner. Clutch felt fine before the bleed..

Figured out that having the car not level (Ass up) pushed any air to the back of the slave, not out the bleeder towards the front of the car so I think I can tackle that tomorrow.

Sounds like I will be pulling the motor this weekend

[aston@ultrasw.c]

Originally Posted by Bravoaloha

The swap was done by a PO but the listing said the following "G50-01 Light flywheel with clutch kit stage 2 from Patrick Motorsport" so I'm hoping I am in the clear on that.

Tried bleeding the slave today and now I have a soft clutch to add insult to injury.

You need to find my genius post on bleeding the clutch 🇬🇧☮🌵

[yelcab1]

Pull the motor. Be done with this task. Stop effing around.

[Bravoaloha]

Originally Posted by aston@ultrasw.c

You need to find my genius post on bleeding the clutch 🇬🇧☮🌵

This one cleared everything up for me. Gonna follow the sequence in post 17.

[aston@ultrasw.c]

Originally Posted by Bravoaloha

This one cleared everything up for me. Gonna follow the sequence in post 17.

Hahaha

[Bravoaloha]

For those following along at home, the clutch bleed seemed to do the trick!! Thanks everyone

[Bravoaloha]

Gentleman! I am back..

Clutch bleeding seemed to do the trick at first but as I drove the car more I am showing the same but less severe symptoms. I bled the clutch a second time as I thought maybe some air was getting into the system because the brake fluid was a bit low.

Brake fluid is now topped off with the system bled and I am still having issues. It is odd to me that the problem is intermittent. No issue when the car is cold and as it warms up. Once she is warm and I start driving hard and shifting around she starts to lock up and not want to go into gear. Left in gear (say fourth) and still driven hard for a time she will then be happy shifting again.

Slow, careful shifts and double-clutching helps but sometimes even with those precautions she won't go into gear (fourth is the worst).

Any ideas? Transmission fluid was changed relatively recently and I would guess under 1500 miles ago.

Thanks!

[walt]

If you've checked the shifter bushings and coupler and verified your clutch travel is correct then you may have done all you can without pulling the trans. If you heard a "crunch" then maybe drain the oil and see if anything out of the ordinary comes out. Just went through this myself.

[Bravoaloha]

Thanks Walt.

I drained the oil. As I mentioned, I changed the transmission oil fairly recently (under 3,000 miles ago). The oil looked ok, dark greenish but pretty transparent. Looks to me like a lot of shavings (I am thinking more than should be there in under 3,000 miles) on the magnet and also a layer of sludge under the shavings (as pictured)

Planning to talk to my mechanic tomorrow.

[icarp]

I had the same problem with my 87 g50 911. It was the master cylinder for the clutch.
Just change it to a new one bench bleed it and install it , I also replaced the slave .
No more problems .

[Bravoaloha]

Originally Posted by icarp

I had the same problem with my 87 g50 911. It was the master cylinder for the clutch.
Just change it to a new one bench bleed it and install it , I also replaced the slave .
No more problems .

Great info icarp, thanks! Were you able to diagnose it figure out it was the master or did you just remove and replace and that fixed the problem?

I would like to know for sure before throwing parts at the car.

[icarp]

I did a full tear down , bought a new one . The seals in my MC were spongey , this allowed for a transfer of fluid from one chamber to another with out the fluid loss .