superbird

When I first got my '90 s4 the first thing I did was check the the flex plate. Sure enough it was in to the engine and observing the undoing of the clamp bolt I did see the flex plate reform. re-torqued to 70 ft/lbs. just checked after, maybe 1k kilometers and it is in again. This time however, when releasing the clamp it did not move out. The flex plate deformation is about 2-3mm and it doesn't seem to causing trouble. when I pried the crank back, it moved 2mm. The drive shaft remained stationary as the flex plate to mounting bracket remained stationary. Has any one seen a flex plate remain bowed?
Concerning the Porken and Constintine fixes. The stock clamp is wielded to the flex plate housing, so tightening the bolt will only clamp the housing to the drive shaft (duh) The Porken Pklamp installed engine side and uptight to the original will only add and additional clamp. At a required 17 ft/lbs per bolt x 2 still gives only 17 ft/lbs overall, so really what help does that give to prevent drive shaft moving? Why not drill the entire assembly through and drive a split pin in?

Landseer

Can you explain a little bit more?

What moved 2mm when pried-back? Hopefully flexplate during pry. (which is what I experienced on an 85, the splines were rusty and it took some slight prying effort to get the plate flat).

I torqued it like you did, then a few months later found about 2 to 3 mm flex (originally it had over 6mm) and then I put a PKlamp on it.

The PKlamp helps put additional squeeze on the factory clamp, kind of an assist, and it seems to be holding well. Bill Ball has a thread tracking its performance.

The Constantine clamp replaces the factory clamp (I don't understand what you said about the clamp being welded to the flexplate). That baby is a piece of mechanical art and will never move.

The overall key is to locate the clamp onto a certain happy place on the driveshaft splines (a place where the flexplate is flat with no tension forward on the crankshaft) and lock it down.

It seems like drilling would cause incredible force concentrations within the shaft during torsion.

brianrheffron

I seem to remember a thread about flexplates where one contributor
found a "permanent" bow to the flexplate that didn't flatten out when
the clamp was released. They released the six bolts that connect
the flexplate to the flywheel, the flexplate flattened out and they then
retorqued the six fixing bolts.

SteveG

Drill through the shaft? I don't think that would work. A bolt large enough to withstand the torque of the engine would significantly weaken the shaft and the coupler.

PorKen

17 ft/lbs to turn the 8mm bolts axially. The clamping force of these two bolts together is very high, plus you have the original clamp. (The original is limited somewhat by being single sided.)

Mongo

What's the torque for these 6 flexplate bolts?

I am having the same issue but have not loosened the bolts.