When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Here are some pictures of the wear on my dual discs and stub/short shaft. My clutch had been making noise and upon opening it up I see the following.
Considerable wear to the front disc splines
What I would call moderate wear to the rear disc. Please correct me if I am wrong here.
and a very worn short/stub shaft.
I am replacing the arm/shifter bushings, release bearing, pilot bearing, both discs (ending in part# .35 and .36 respectively) with new, and the stub shaft with a used unit seen at the bottom of this post. (please comment if this shaft is in acceptable condition) Note the dark spot on the portion of the shaft that goes into the pilot bearing. Is this a problem?
There were no signs of the super duper special Porsche grease on these parts. Is this what caused this failure, and/or a poorly adjusted clutch?
I have to assume since the splines in the front disc have had their points almost completely worn away that the clutch must have been dragging for some time. Is what one sees here indicative of such wear?
Will the application of the special grease and the new parts keep this from happening again?
Does this used short shaft seen below look acceptable?
Here are some pictures of the wear on my dual discs and stub/short shaft. My clutch had been making noise and upon opening it up I see the following.
Considerable wear to the front disc splines
What I would call moderate wear to the rear disc. Please correct me if I am wrong here.
and a very worn short/stub shaft.
I am replacing the arm/shifter bushings, release bearing, pilot bearing, both discs (ending in part# .35 and .36 respectively) with new, and the stub shaft with a used unit seen at the bottom of this post. (please comment if this shaft is in acceptable condition) Note the dark spot on the portion of the shaft that goes into the pilot bearing. Is this a problem?
There were no signs of the super duper special Porsche grease on these parts. Is this what caused this failure, and/or a poorly adjusted clutch?
I have to assume since the splines in the front disc have had their points almost completely worn away that the clutch must have been dragging for some time. Is what one sees here indicative of such wear?
Will the application of the special grease and the new parts keep this from happening again?
Does this used short shaft seen below look acceptable?
Yes, very worn. Very typical when the shaft isn't properly greased.
Won't happen if it is properly greased.
Used shaft looks ok to me. That dark where the pilot bearing goes on shouldn't be a problem. Is it pitted? Or just discolored?
Even if it's just a bit pitted, the pilot bearing is fitted to it fairly loose (it's a 'sorta press' into the back of the crank), so it shouldn't be a problem as long as the pilot bearing can fit easily on to it.
Thank you WJ! The dark spot is a bit pitted . Only a few thousands of an inch in raised pittedness (is that a word Probably no more than 5-7 thousandths though.
Again, it's not a tight fit, the shaft is supposed to go into and out of it easily.
Maybe clean it up a bit with some emery cloth or similar.
If it were me, I'd chuck it up in a lathe or drill press, turn it reasonably slowly and use a light touch with fine emery cloth, sandpaper or steel wool.
And, as always, I can be wrong. If one of the folks with real knowledge disagrees, listen to them.
I can see spline wear as I've marked, on that used stub shaft, where the front disc hub splines have started to eat into the shaft spines. It also looks like, from the bluing, that the front may have been spinning in a seized pilot bearing.
I wouldn't use the stub shaft, particularly as you're fitting new driven discs, because the worn splines will allow rotational slop, which will worsen the shaft spline wear, and cause earlier disc hub spline wear on your new discs. Spline wear also causes hangup of the discs on the splines, which causes trouble with disengagement. The nose bluing is less of a problem, providing the diameter hasn't been reduced.
GB has a harder replacement, which Roger probably stocks.
Knowing how temperamental DD clutches are, IMO you're more likely to have issues using less than ideal components ... and in this case run the risk of prematurely damaging your new discs.
Dave I apologize for my late response. Thank you very much for your input. I decided to go with Greg B at Precision's custom made one. I just got the car back today. It's been since thanks giving.
it running anyway. The "new" used transmission has some synchro issues as well, but at least I have it going and can send my old one out at my convenience. There is a bit of a whirring grinding sound from the rear when turning though. not sure what that is. I does not sound like CV joind clunking, but I am not sure.
There is no side loading on the trans when going around a corner, so a grinding rumble is almost undoubtedly wheel bearing related. It may be a dufo bearing, and may also be due to the nut on the stub axle being a little loose. It needs 326 lbs/ft.
The rear bearing is a double-row angular ball bearing with a split inner race. The tension on the stub axle squeezes the inner races together to provide the preload on the bearings. Not enough tension will quickly destroy the bearing.
You can torque the bearing without a torque wrench. If you have a big enough breaker bar and socket, calculate the torque delivered when you stand on the bar at a specific spot. Your normal body weight is needed. Then 3912 divided by your body weight in pounds gives you the number of inches from the center of the nut where your weight should be applied. Bar needs to be horizontal, and it needs to be a dead weight on it, no bouncing. (3912 is 326lbs/ft x12 to get inches as the result)
07-15-2017, 01:29 PM
'78 dual clutch disc / shaft splines wear ...How to avoid?
Probably no more than 5-7 thousandths though.
