911 SC Clutch backlash?

[toreboee]

Tried searching the forum and found a lot of good info, however I'm not sure my particular problem was addressed. If it did and I missed it, I apologize.

1982 911 SC 150k miles. Last documented clutch change, as far as the receipts that came with the car can tell, was September 2000 at 120k miles.

The car is difficult to drive at low speeds because it starts jerking on the drive train when getting off the throttle. There is a mechanical clinck clunk sound. The CV joints seam pretty solid with very little play. Installed wevo engine mounts yesterday. The problem became more pronounced.
I have to either depress the clutch, increase power, or apply some brake to make it stop. In other words I need to introduce some tension to the drive train to limit the bucking/jerking.
Please look at this video where I rock the wheel back and forth and see if it looks familiar 911 SC clutch backlash? - YouTube

Thanks!
Sincerely Tore

[Reiver]

Are you sure it is the clutch and not another issue. Hunting (up/down) surge is often a too rich AFR and is usually only evident at idle speed.

[toreboee]

Thanks for your reply Reiver. I'm not sure it's the clutch, however as you can see in the YouTube video I'm rocking the car back and forth when it's parked and in 1st gear. Therefore I don't think is surge or hunting as you mention. I could be wrong though
As long as there is tension on the drivetrain everything is smooth. On flat ground coasting along in first or second however, it will start jerking back and fourth without any change in engine pitch. It's as if the mass of the car tries to overtake the drive train/wheels and bounces back, then the opposite happens and the motion become amplified until I stop it using one of the before mentioned techniques. Brake, accelerate or depress clutch.

[Reiver]

I did the same to my car in first gear, same exact noise...that is not the issue...what you are hearing is drive train engagement when you rock the car.
Have your emissions tested for CO level...you may be too rich. When that happens and the car has limited torque applied....say going slightly downhill in gear at idle...it will 'search' and rev up/down creating a bucking scenario.

[porwolf]

Are you sure you have the steel spring clutch in there. My original 1979, rubber spring clutch, had the same symptoms when it disintegrated. It was replaced with the steel spring clutch and I never had a problem since.

[Reiver]

He's had a clutch change...no one puts that rubber centered disc in unless they are brain dead. OTOH, there are brain dead folks about (mostly elected officials of late) but most mechanics are smarter.

[toreboee]

Thanks guys for the input. Looks like I have a bit of investigating to do. Emissions or clutch. Assume I can only find out for sure if its a rubber center clutch by dropping the engine.
I read about the limp home mechanicals making it possible to drive with a disintegrated rubber center and was afraid that could be it. Went for a test drive and It does not feel like a throttle surge causing it.

[Reiver]

Good luck.
I jumped into Norway, Sandefjord, in '78 with the 509th Abn Bn combat team. The locals treated us fantastically.
I enjoyed the visit.

[Flat6pac]

Make sure the verticle shaft to the release fork operates freely on the shaft.
Take down the small clutch lever then see if the large arm with the spring will pivot freely on the verticle shaft. This arm must be free to pivot and they do freeze on the vertical shaft.
Bruce

[porwolf]

Originally Posted by toreboee

Thanks guys for the input. Looks like I have a bit of investigating to do. Emissions or clutch. Assume I can only find out for sure if its a rubber center clutch by dropping the engine.
I read about the limp home mechanicals making it possible to drive with a disintegrated rubber center and was afraid that could be it. Went for a test drive and It does not feel like a throttle surge causing it.

Just thinking: Could you not jack up the car on one side. Put the transmission in the 5th gear. Then try to move the raised back wheel back and forth. If the clutch rubber springs are severely disintegrated you may feel lose slack in the drive train.

I have never don that. Maybe someone can chime in here?

[kodioneill]

I had the same problem and it was the engine and tranny mounts.

[toreboee]

Originally Posted by porwolf

Just thinking: Could you not jack up the car on one side. Put the transmission in the 5th gear. Then try to move the raised back wheel back and forth. If the clutch rubber springs are severely disintegrated you may feel lose slack in the drive train.

I have never don that. Maybe someone can chime in here?

Porwolf, I did what you suggested and when I turn the tire the outer diameter moves 1,5 inches relative to the floor in my garage. Is that enough evidence you think? Shot rubber center

Kodioneill, I just installed new engine and tranny mounts. I thought that could be part of the problem as well, however it did not help.

Starting to wonder if its the tranny diff or some other internals. The tranny was rebuilt about 30k miles ago. Would think it should last longer.

Both clutch and tranny was done by Kahler's in Dublin California around the same time in October 2000. I don't know anything about the shop, however I assume they knew what they were doing. I know I should not assume but I'm a business major

Thanks again for all feedback

[toreboee]

Originally Posted by Reiver

Good luck.
I jumped into Norway, Sandefjord, in '78 with the 509th Abn Bn combat team. The locals treated us fantastically.
I enjoyed the visit.

Thanks Reiver,

Glad you enjoyed Sandefjord

[tirwin]

Don't know if this would help or not but could you open up the tunnel cover in the back seat and get someone to see if there is movement along the axis of the shift coupling when you roll the car back and forth like you're doing in the video?

[toreboee]

Dropped the engine to check for oil leaks and investigate the clutch. The clutch looks fine. 7,7 millimeters thickness on disc. (Its not a rubber center disc)
The play is in the transmission main shaft which connects to engine. Is this normal? I can turn the shaft side to side about 1/2 - 3/4 inch.
I realy want to get ridd of the click clack jerking when driving at low speeds/slow traffic.

[theiceman]

Originally Posted by toreboee

Dropped the engine to check for oil leaks and investigate the clutch. The clutch looks fine. 7,7 millimeters thickness on disc. (Its not a rubber center disc)
The play is in the transmission main shaft which connects to engine. Is this normal? I can turn the shaft side to side about 1/2 - 3/4 inch.
I realy want to get ridd of the click clack jerking when driving at low speeds/slow traffic.

PM Pete Zimmermann , he will know right off the top of his head what you should be seeing.

[toreboee]

Thanks Iceman,

I'll try Zimmermann