Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 911 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
CHP-POR's Avatar
 
Join Date: Jan 2000
Location: Virginia
Posts: 111
Garage
Diagnosing the actual problem? (grinding reverse)


Symptom: grinding when trying to get into reverse, and 1st, but not as much.
My body man was saying how much effort and travel was required to move the car around, so after getting the car back I've been all through the clutch adjustment procedure today.

First off I discovered that the helper spring was not set up correctly, it was not loaded because the pin protruding from the spring mount shaft was behind the stop tab. (I'm not sure how the arm was able to move forward to disengage the clutch without being blocked by the tab that stops it from going back come to think of it, but it did)

After getting the helper spring in right and setting the 1.2mm gap, my cable was far too extended to be near the correct position, and I had to rotate it to screw it all the way in at the pedal cluster. Eventually I was able to get the slack out of the cable between the arm and the cable mounting nuts and close the gap to 1mm, but there is excess cable "bunched" toward the firewall (maybe 1" or even 2" longer than necessary), leading me to question if the cable is as effective as it could be.

I still don't have a pedal board with a stop, so I had a helper depress the clutch as much as would "seem" normal to shift, and only got 16mm travel. Then I had them press it "all the way", and the travel was 25mm per the instructions. I guess that is OK, although I will know better when my pedal board with stop is installed. It seems like that was an excessive amount to have to push the clutch to get the needed 25mm. Hopefully that would not be necessary to shift while driving! The seat was way forward and the toe extended to get the 25mm.

So, the setup is technically correct as far as what I have been able to read. The pedal is firm and starts to pull right away (no pedal slop).

Now, getting into first is possible but requires absolutely everything.
Getting into reverse is impossible without grinding. If fact, I start to hear a nicking sound if I depress the clutch as far as I possibly can, and still it grinds (the gear is seriously spinning)

I am looking for some help from you guys who've been doing this a while. Is it:
1) cable to long (car is a '76, don't know what year 915 is, but not original, maybe the cable I ordered for '76 is off a little).

2) damaged pressure plate diaphragm from previous incorrect setup (pedal being mashed to floor since pedal stop absent). Seems unlikely since I think damaging the diaphragm would be evident with engagement problems not release problems.

3) I have a throw arm mis-matched to my transmission? I'm not familiar with the number of changes that may have taken place, but I think there was a change in '77 to use the helper spring. My car matches the pics in the 101 projects article.

4) I have transmission in need of work

or none of the above?

I'd sure appreciate any tips to help figure this out.
__________________
Rich
'76 Coupe
Old 08-09-2011, 07:50 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Member 911 Anonymous
 
DRACO A5OG's Avatar
 
Join Date: Sep 2007
Location: Rancho Palos Verdes
Posts: 14,290
Garage
Send a message via Skype™ to DRACO A5OG
Where in the pedal travel does the clutch engage? It should be in the middle of travel.

Is the clutch pedal even with the brake pedal height? If properly adjusted it should be the same level.

If all properly adjusted, touch one of the gears before going into reverse.
__________________
'85 Carrera Targa
Factory Marble Grey/Black * Turbo Tail * 930 Steering Wheel* Sport Seats * 17" Fuchs (r) * 3.4 * 964 Cams * 915 * LSD * Factory SS * Turbo Tie Rods * Bilsteins * Euro Pre-Muff * SW Chip on 4K DME * NGK * Sienes GSK * Targa Body Brace
PCA/POC
Old 08-09-2011, 10:13 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Jul 2000
Location: So. Calif.
Posts: 18,358
Sounds like the clutch cable is slowly dying (some cable strands are failing).

MHO,
Sherwood
Old 08-09-2011, 11:06 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
CHP-POR's Avatar
 
Join Date: Jan 2000
Location: Virginia
Posts: 111
Garage
Forgot to mention the cable was new.
The clutch engages somewhere mid-way, approximately.
The brake and clutch pedals are even with each other.
__________________
Rich
'76 Coupe
Old 08-10-2011, 11:41 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
Join Date: Jul 2000
Location: So. Calif.
Posts: 18,358
Quote:
Originally Posted by CHP-POR View Post
Forgot to mention the cable was new.
The clutch engages somewhere mid-way, approximately.
The brake and clutch pedals are even with each other.
Correct new cable? It should be compatible with the gearbox number stamped on the bottom of the housing.

Sherwood
Old 08-10-2011, 11:50 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
Peter Zimmermann's Avatar
 
Join Date: May 2008
Posts: 2,898
This symptom is typical for a release bearing operating fork beginning to break. The fork has two "fingers" that grab the T.O. bearing. One or both (usually just one) of those fingers can crack, and when that happens a bit of light 1st/R grinding (incomplete clutch release) will occur. Usually a clutch adjustment (reducing the amount of pedal free-play) will help, but only for a very limited amount of miles, and then the problem will return as the fork's finger cracks even worse.

You say that the car is a '76, but that year model uses a straight cable with adjustment and lock nuts. Beginning with '77 the car requires a cable with a straight hook on its trans end. That style cable, used through '86, is available in two versions, (1) an original replacement that costs about $100, and (2) a real POS after market cable that sells for about $40. The after market cable might say "Made In West Germany" in white letters on the black bowden tube. If you have that cable throw it away and get a factory original unit.

A second problem can be a roll pin, on the pedal assembly clutch shaft, breaking.

BTW; with the '77 and later release system you can't (shouldn't) be able to feel free-play at the pedal.
__________________
Keep the Shiny Side UP!
Pete Z.
Old 08-10-2011, 11:55 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
CHP-POR's Avatar
 
Join Date: Jan 2000
Location: Virginia
Posts: 111
Garage
I rebuilt my cluster and installed the brass bushings so I'm confident that is no issue here.

With my current adjustment, there is no free-play. While I don't like the "extra" length between the firewall and the adjustment nuts, theoretically when pulling it shouldn't matter.

I looked at the cable offerings here, and I definitely have the right one for the >= '77, but I'll have to look closely for the POS id. Noticed that our host sells one for $60 (GEMO) and I think it's the one I bought but it was @4 yrs ago so I can't remember. Is that the POS version?

Pete, found this thread that describes what you brought up:
Clutch Fork Broken or Adjustment Problem?

My gut tells me this is what is going on, I just would never have suspected it was a possibility. In my OP I mentioned hearing a "nicking" sound when pressing the pedal to the max depth, which I'm sure is the diaphragm tabs contacting something. Is such contact possible with a good fork simply by over-extending the PP release direction? Ever heard the nicking sound I am talking about?

I'll report back later. Thanks for the insights!
__________________
Rich
'76 Coupe
Old 08-11-2011, 05:46 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
Peter Zimmermann's Avatar
 
Join Date: May 2008
Posts: 2,898
Quote:
Originally Posted by CHP-POR View Post
I rebuilt my cluster and installed the brass bushings so I'm confident that is no issue here.

With my current adjustment, there is no free-play. While I don't like the "extra" length between the firewall and the adjustment nuts, theoretically when pulling it shouldn't matter.

I looked at the cable offerings here, and I definitely have the right one for the >= '77, but I'll have to look closely for the POS id. Noticed that our host sells one for $60 (GEMO) and I think it's the one I bought but it was @4 yrs ago so I can't remember. Is that the POS version?

Pete, found this thread that describes what you brought up:
Clutch Fork Broken or Adjustment Problem?

My gut tells me this is what is going on, I just would never have suspected it was a possibility. In my OP I mentioned hearing a "nicking" sound when pressing the pedal to the max depth, which I'm sure is the diaphragm tabs contacting something. Is such contact possible with a good fork simply by over-extending the PP release direction? Ever heard the nicking sound I am talking about?

I'll report back later. Thanks for the insights!
Yes, Rich, post #8 in your thread link shows a broken fork.

Regarding clutch cables, it's likely that the after market one is a GEMO, but I can't say for sure. Look for that "Made in West(ern) Germany" on the bowden tube! It is highly likely not a factory cable, because I'm pretty sure those have been over $85-90 for quite a few years.

When we had a car with a clutch release problem towed into the shop we usually pushed the car onto a hoist for diagnosis, rather than try to drive it. If a fork has a broken/breaking finger, it will pull the TOB/pressure plate at an angle, so I suppose a cyclic noise from unusual contact could result.
__________________
Keep the Shiny Side UP!
Pete Z.
Old 08-11-2011, 04:36 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
CHP-POR's Avatar
 
Join Date: Jan 2000
Location: Virginia
Posts: 111
Garage
engine-out update

Here's an update now that the engine is out.
The release fork is not broken.

After getting things apart what I have found is that the fork has not failed, but it appears that the pressure plate is too far extended into the bell housing.
This causes the "initial angle" of the fork when on the t/o bearing to be insufficient, so in effect the arc of the shaft rotation is starting too late and running out of room in the bell housing with the pedal on the floor (no board or pedal stop in place).
I had described a "nicking" sound. That is the diaphragm tabs contacting the fork shaft bosses, shaving bits of aluminum off.

My steel flywheel and AL adapter are from Renegade Hybrids, the pressure plate is from Kennedy engineering. (don't ask why, this has been muddling forward off and on for 10 years and started with a box of stuff picked up in a trade, I can't remember the basis for past choices) The crankshaft is 1966 Chevrolet, small journal 327, if that were to matter. Maybe the flanges were thicker than later ones?

I measured 66.5mm from the bell-housing mating surface of the RH adapter to the outermost edge of the aluminum part of the pressure plate.

So with that background, I need to find out the correct distances are between components, and which component(s) would be best to remove material from.
__________________
Rich
'76 Coupe
Old 09-12-2011, 05:54 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
CHP-POR's Avatar
 
Join Date: Jan 2000
Location: Virginia
Posts: 111
Garage
Can anyone tell me your observed distance between the block face and the flywheel surface (clutch contact)?

And/OR from the block face to the to rear edge of the t/o bearing?

Something in my stack-up is not right.

Thanks
__________________
Rich
'76 Coupe
Old 09-16-2011, 08:01 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
CHP-POR's Avatar
 
Join Date: Jan 2000
Location: Virginia
Posts: 111
Garage
bump ... anyone have an engine out that could take some reference measurements for me?
__________________
Rich
'76 Coupe
Old 09-21-2011, 10:42 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Member 911 Anonymous
 
DRACO A5OG's Avatar
 
Join Date: Sep 2007
Location: Rancho Palos Verdes
Posts: 14,290
Garage
Send a message via Skype™ to DRACO A5OG
Ah Man, Just had mine out to service the Main Shaft Seal.

Do you have pic of yours if dropped?
__________________
'85 Carrera Targa
Factory Marble Grey/Black * Turbo Tail * 930 Steering Wheel* Sport Seats * 17" Fuchs (r) * 3.4 * 964 Cams * 915 * LSD * Factory SS * Turbo Tie Rods * Bilsteins * Euro Pre-Muff * SW Chip on 4K DME * NGK * Sienes GSK * Targa Body Brace
PCA/POC
Old 09-21-2011, 12:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Registered User
 
CHP-POR's Avatar
 
Join Date: Jan 2000
Location: Virginia
Posts: 111
Garage
It's out with the trans parted from the engine. Currently distracted with a cam change.
My plan is to mate everything while out and use a pipe or something to actuate the arm and observe travel. I've talked to Kennedy and Renegade and we can't find anything that seems to be out of spec.

My daughter absconded with my camera to college, so I'm waiting for my new one to arrive. Will include some pics soon as I can.
__________________
Rich
'76 Coupe
Old 09-21-2011, 03:52 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 06:21 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.