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I agree that the weld will become an integral part of the structural support once the R clamp is installed, but as for failure of that weld: I believe it is a near impossibility that it could fail in a way that would render the R clamp ineffective. I you will notice the weld is on the rear side of the clamp. being on the rear side the clamp means that the weld is in compression. With the weld in compression the chance of failure is virtually 0. Yet even if the weld were to fail, the chances that the failed weld would render the R clamp ineffective are equally low, since the only way the clamp could migrate aft would be if the weld failed precisely along the surface plane of the coupler. With a fracture plane above the coupler there would still be a mechanical limiter of the clamp since it would butt up against the remainder of the weld still affixed to the coupler, and if the weld fracture line dipped into the coupler the clamp would essentially have a tooth that locked it into the divot in the coupler again preventing the aftward movement of the clamp.
While the chance of failure of the weld may be virtually 0, in your mind, the reality is that the welds do fail and the clamps do become detached, from the flex plate. Since the Ritech clamp totally depends on the location of the flexplate clamp (and thus that tiny tack weld), as soon as the clamp is detached from the flexplate assembly, the Ritech clamp becomes extra "nothing" hanging onto the clamp....doing absolutely nothing to prevent shaft migration.
The torque tube shaft is going to pull out of the flexplate, exactly like it does, in the totally stock configuration.
Not wander to far off the topic, but I've always thought we should celebrate 9/28 each year by performing health checks on our cars. Crankshaft end play could be one, fuel line inspection another. Basically, an annual PPI.
I have not experienced or seen a weld break on the original clamp. Not saying it does not happen but the % failure rate must be pretty low. You know you could also get in an accident with your 928 or forget to put oil in the engine and on the low chance of that happening decide to do NOTHING!!!
However I think we digress again.
Please check the end float of the crank and then make your choice depending on the result and your own peace of mind.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
I'm talking about checking for movement as someone works the clutch. If the clutch is putting that much pressure on the crank to load up the thrust bearing, you'd be able to measure that movement on an otherwise perfectly good engine.
I saw evidence that the clutch is exerting pressure enough to cause wear on the thrust bearing when I participated in a rebuild of the motor in Dennis Kao's 5-speed.. Thrust bearing was worn through to the copper on the front side. Back side was pristine. Endplay was still OK.
Well, I understand that.....and realize that you're invested in this problem.
However,
If the torque tube is out and being repaired (which is really common, these days), a new 25mm torque tube shaft, with Mark Anderson's new bearings and counterweight rubbers, along with the Porsche shaft circlip, washer, and shims, is cheaper than a either a Ritech or Constantine clamp and Constantine's bearings.
And it fixes the problem, instead of patching it and still having grief, down the road.
We did exactly what Greg recommends several years ago in a 90 S4 that broke its TT shaft. With the right circlip tool (small, cheap one in this case), getting the circlip on the end of the earlier 25mm shaft, the hardest part of the job, was easy.
The bearing, circlip and washers retrofit is something that even Porsche stopped using in 1984. The only problem was Porsche not re-designing the front flex plate clamp to work by itself.
If you want to use the bearing, circlip and washers on your 25mm drive shafts, then you need to follow the Porsche WSMs on how to set it up correctly. By all accounts, and as someone keeps reminding us, Porsche spent millions of dollars designing that system so who should second guess on how to use these parts and set it up correctly.
By "correctly" the WSMs show a gap between the flex plate and flywheel that needs to be measured and kept by using the correct shim thicknesses at the front, before the flex plate is bolted to the flywheel. Not doing so could cause the retrofit of these parts to not control the drive shaft pullout at the front flex plate.
Thankfully no one has to use these old parts and pieces anymore due to the different devices available to do this job better than initially designed.
Last edited by Constantine; 06-25-2019 at 06:53 PM.
Reason: Added WSM page about spacing requirements
Do I understand it correctly that the factory clamp in the front tends to slip in automatics while it holds in manuals? Is this oversimplifying the issue?
Does the rear clamp that holds the drive shaft and the fifth gear together slip with manual transmission cars?
I understand these are novice questions, just trying to understand the manual car driveline better.
06-14-2019, 03:52 PM
George Layton March 2014
