Mike Frye

These are all doing the same thing (or attempting to) which is overcome the force trying to push or pull the flex plate because it's fixed to the front end of the drive shaft. I was just wondering if it would work more like a manual tranny if it were able to slide a bit front to back, and just use the collar to turn the drive shaft.

I'm completely naive about the forces at work here, I just don't remember it being discussed as an option in all the threads I've seen about this.

Bill Ball

I think Constatine may have worked on the idea of a sliding joint as well. Or at least it has received some speculation here. The shaft would have to be custom made with more subtantial teeth to mate with a more subtantial sliding collar to take the torque w/o stripping or breaking.

Mike Frye

Ah, that's news to me. I didn't see anything in the threads I'd read about it. Thanks Bill.

From everything I've read, Constantine's clamp is the right way to go if you don't ever want to worry about it again. Alternately, setting it up so it's easy to check periodically seems like it would be easy enough (either cut or remove the rear bell housing bolt or get crossovers). If you have a set of liftbars from Porken or a lift, It's not much more difficult than changing the oil. I just thought it might work since it clearly wants to slide anyway.

marton

About
Could be but why does it ratchet in only one direction? Also when the bolt is released the flex plate has enough tension in it to return to the correct position without help; so wouldn't that resist the ratcheting effect?

Marton

Mike Frye

The way I understand it from looking at it and reading stuff on here from Constantine and others it works like this:

The torque from the engine is applied to the flex plate, which is bolted to the drive shaft at the pinch collar. There's a tremendous amount of twisting force on the drive shaft. So much so that the shaft actually gets shorter, which makes the collar slide on the spline. When the torque is removed on decel, the only force acting on it is the amount within the flex plate that wants to return to its original shape, but this is less than the amount of clamping force applied to the collar by the bolt.

Apparently the holes for the six bolts at the edges of the flex plate are enough larger than the bolts that they can actually hold the flex plate in the bowed position as well (as Adam found out yesterday when we released the collar and still had a bow in the plate until he loosened those bolts as well). So the pulling force of the twisting drive shaft is stronger than the clamping force of the six perimeter bolts plus the pinch collar bolt, but the clamping force of those bolts is stronger than the tendency of the flex plate to spring back to flat, hence the 'ratchet' effect.

Black Sea RD

Mike,

Your last post nails it pretty well except the part about the six bolts holding the flexplate onto the flywheel. These really don't have that much to do with holding onto the drive shaft. The lone pinch bolt in the front flexplate clamp as well as the design of the clamp is what holds onto the drive shaft. Not very well I might add.

I did make a sliding coupler affair that I tried early on. Too noisy since the drive shaft end was just floating in the new coupler and the engine vibrations made it rattle within itself. The noise went away with RPMs but was totally unacceptable.

To continue this floating coupler fix was to re-design the front drive shaft area and the costs would have been too much and the end user would have a more complicated system.

That's why we went with the new clamp. Take Porsche's design element and just make it better, as they should have done in the first place, IMHO.

Not to use the pinch bolt in the old clamp would invite disaster, as in a stripped drive shaft, clamp or probably both. The metal was not heat treated correctly at the drive shaft end and clamp for this use and the tolerances between the splines and coupler are also incorrect.

HTH,
Constantine

Mike Frye

Hi Constantine,

I'm pretty sure you've considered this situation more than anyone and I'm sure your solution is the best one along the lines of the original intent. The collar without the bolt isn't enough to hold it. I wasn't aware that you'd tried a sliding collar idea, I think that's cool and it's pretty much what I was thinking of.

What I meant by the six bolts was not that they secure anything to the drive shaft, but that they are part of what is working against the twisting force, since they can actually hold the flex plate in the bowed position and need to be loosened before the plate will straighten out completely (at least that's what happened in this case). The six plus the collar bolt (as nearly as I can tell) are all working against the flexing of the plate, but eventually end up moving slightly in response to the torque of the engine, and are tight enough to resist the flex plate returning to its original shape.

Thanks for the detailed response. I see it wasn't a new idea, I just hadn't read it discussed anywhere. There are quite a few threads on this and I must have missed it.

Oh well, thanks for the responses everyone, I guess all you auto guys will just have to keep up your maintenance schedules or just buy one of Constantine's clamps and never have to worry about it again.