Flex-Plate Warning...

mrrsm

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While rummaging around for all the New Parts that are going along with a gifted 3,4L V-6 Engine… I dug down inside of the box holding a pristine Flex-Plate and THIS Warning message was printed on an 8”X11” Color Flyer inside:

Warning:

The Warranty is VOID if the Flex-Plate Assembly is Broken around the Crankshaft and/or Torque Converter Bolt Pattern…. (The Warning is repeated…)

The Warranty is VOID if the Flex-Plate Assembly is Broken around the Crankshaft and/or Torque Converter Bolt Pattern….

Reduce Failure:

Check Engine and Transmission Mounts and be sure they are supporting Drive Train properly.

Replace Broken-Worn-Out Motor Mounts… Match New Part to Part being replaced… Always use a Torque Wrench … Never Over-Tighten or use an Air Wrench… Use New Flex-Plate Bolts.

So… in support of the great write-up done by @Capote last September 2016 regarding him conquering the odd destruction of the center of the Flex-Plate in The BatBlazer:

https://gmtnation.com/forums/thread...ll-knocking-bottom-end-troubleshooting.15534/

I thought this information might be worth adding or remembering if the Motor Mounts or Transmission Mounts have NOT been replaced and this Flex-Plate Cracking Problem gets discovered requiring that they get R&R'd.. Apparently, the company making the Flex-Plates has determined that the Failed Motor Mounts are involved as a direct cause for this kind of Flex-Plate Cracking Failure. Here is a link to the scanned image of their Warning Flyer of the text echoed above:

http://s557.photobucket.com/user/60dgrzbelow0/library/FLEXPLATEWARNING?sort=3&page=1
 
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Capote

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Hmm, never heard of any warning like this before associated with flex plates.

I know that in my case at least, it was because of one of the torque converter bolts walked out just enough to make contact with the bell-housing, whilst rotating at very high speed of course. That bolt was even marred down a bit. This had to of caused small stress fractures that ultimately lead to my flex plate cracking around the hub. Because in that thread of mine you linked, that issue occurred shortly after this incident with the loose bolt.
 
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mrrsm

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Of course... but as soon as I saw this damned thing I thought, "Wow... This kind of makes perfect sense..." because if the entire engine is being bounced around on as many as three contact points, ostensibly "Gel-Filled" when new; but then empties out when they get ripped or worn open... when they SHOULD have been absorbing the vibrations and restricting how much actual "Motor Shaking" has been going on.

Meanwhile... the TCs have been taking the brunt of all that hectic extra motion; AND rotating up and down the RPM Scale... so in reflection, it might have the effect of pulling and pushing on the TC to FP Fasteners, moving in and out very dramatically. We never did come up with an absolute theory that everyone could agree upon about the ultimate cause of the problem... and so the first person that came to mind with some Primal, Hands-On Expertise on the matter and with mechanical evidence and proof of a cause (Loosened Bolt) ...was You. :>)

Anyway... I thought it was worth your attention, right along with anyone else who stumbles across this problem...and may not be aware that some of the people actually MAKING these Flex-Plates were concerned enough about it to wrap this Bad Motor Mount Idea around their Product Warranties ...with a Pink Bow ...to let people know that their's would be worthless if any FPs failed and got sent back loaded with those Infamous Cracks around the Crankshaft Flange and/or the Torque Converter Mounting Bolt Holes at 120 degrees apart. But Motor Mounts? Who Knew? Weird.. Huh?
 
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Capote

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Of course... but as soon as I saw this damned thing I though, "Wow... This kind of makes perfect sense..." because if the entire engine is being bounced around on as many as three contact points, ostensibly "Gel-Filled" when new; but then empties out when they get ripped or worn open... when they SHOULD have been absorbing the vibrations and restricting how much actual "Motor Shaking" has been going on.

Meanwhile... the TCs have been taking the brunt of all that hectic extra motion; AND rotating up and down the RPM Scale... so in reflection, it might have the effect of pulling and pushing on the TC to FP Fasteners, moving in and out very dramatically. We never did come up with an absolute theory that everyone could agree upon about the ultimate cause of the problem... and so the first person that came to mind with some Primal, Hands-On Expertise on the matter and with mechanical evidence and proof of a cause (Loosened Bolt) ...was You. :>)

Anyway... I though it was worth your attention, along with anyone else who stumbles across this problem...and may not be aware that some of the people actually MAKING these Flex-Plates were concerned enough about it to wrap this Bad Motor Mount Idea around their Product Warranties ...with a Pink Bow ...to let people know that their's would be worthless if any FPs failed and got sent back loaded with those Infamous Cracks around the Crankshaft Flange and/or the Torque Converter Mounting Bolt Holes at 120 degrees apart. But Motor Mounts? Who Knew? Weird.. Huh?
It does make sense after all; unwarranted vibrations wreak havoc.
 
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Mounce

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Mar 29, 2014
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At the same time I find it hard to believe that a loose mount could cause that. The trans and motor are bolted together as one solid unit, other than the vibrations going through the metals, it's not like the trans is wobbling around separate from the motor, again they're bolted together. Very little to no flex between the two. Idk, just doesn't seem logical. I've seen motors and transmissions practically falling out of vehicles, completely worn out/broken mounts allowing 5 inches of flex and never once thought it would damage the flex plate. It'll eat the other mounts, yeah, but I don't see it doing internal damage as such.
 

mrrsm

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Please forgive this as being a fairly complex reply.... but for starters, we can agree with the idea that once the Motor and the Transmission are Bolted Together Firmly with 11 sturdy fasteners they behave as One, Single Massively Heavy Component. But that is NOT where the problems lies...The Problem lies IN BETWEEN THEM... WITHIN THE BELL HOUSING where all the movements of the Crankshaft and Flex-Plate and Torque Converter... converge, for there is a very great deal of opportunity for the "FLEX"- Plate to "FLEX" and for the Torque Converter itself... no matter how firmly attached to the Flex-Plate by those 10.9 Bolts ...will STILL be able and tend to slide back and forth innumerable times on the large shaft of the Transmission Axle leading into the Transmission Hydraulic Fluid Pump. This behavior is best illustrated by viewing this video in slow motion at around 31 Seconds into the Instructional Film:


Additional to understanding this situation are Three unmanaged physical forces that could be causing the damage due to a lack of Motor and Transmission Mounts doing there jobs properly:

(1) One Force involved that I did not consider during the 09/2016 posting is the that of INERTIA:

"Inertia ...is the Property of Matter by which it tends to either Remain at Rest... or Remain in Motion... unless acted up by an Outside Force..."

In short... Mother Nature likes things that are NOT moving...to sit nice and still unless some External Force is applied to get such objects Moving. Conversely... She likes things that are Already Moving ...to Continue Moving unless some external force is applied to change its direction or bring it to a Stop.

(2) In this case... the Second Actor involves is that of Gyroscopic Force. If you want to see what this feels like first hand and how much resistance a Gyroscope can create... just hold both sides of a 24" Bicycle Tire by the two ends of the Axle... and after someone spins the wheel up to a decent speed... just TRY and move the Axles points with your hands... You will find this VERY hard to do...and the faster the Wheel is spinning...the Harder it will become to move the Axle out of position.

But in the case of our Vehicles... Instead of using that 24" Bicycle Wheel... make that the Spinning, Fluid Filled Torque Converter...and instead of your bare fingers holding on ...transpose that from the Axle outwards upon the face of the Flex-Plate at the Three Torque Converter Bolts located 120 Degrees apart... When the Vehicle Changes direction ir the RPMs go up and down the scale... those forces are causing the Flex-Plate to Bend and Warp to compensate for all that Gyroscopic Force due to the Conservation of Angular Momentum. This video will demonstrate how those forces occur and what happens to them when they cannot be contained:


This principle is at play in all Aviation Inertial Guidance Gyroscope Systems that rely upon a Massive Spinning Object to remain in one position... irrespective of the direction that the Airplane moves. The bolts holding the Flex-Plate to the Crankshaft Bolts are experiencing this very same Gyroscopic Force of trying to resist the TC when any side to side motion is induced... and the metal of the Flex-Plate begins to bend back and forth to comply... eventually work-hardening, fatiguing and cracking as a result if the induced stresses exceed the ability of the Thin Flex-Plate to do so.

(3) The Third Force involved here is that of Angular Momentum (...it's conservation makes weird things happen with all rotational bodies) . It comes into play as well in such cases... when any Torque or External Force gets applied to the rotational body or system ...and it is felt 90 degrees from the point of the external force being applied. Such random motions of the Engine Block and Transmission are naturally transmitted into the rotational assembly via the Flex-Plate and Torque Converter as they tend to bounce around on bumpy roads or in each and every case when the vehicle deviates from moving ahead...in a straight line...such as when turning either left or right turns...with the motor tending to roll or bounce in the directions opposite to those turns. Just imagine how difficult the random actions of so many external forces upon it for such as the Thin Metal Flex-Plate to resist.

Think of it this way... you have the Torque Converter...a very heavy, ovate cylinder filled with Hydraulic Fluid ... rotating at very high RPM that is connected to the source of the rotational power at the center of the Crankshaft... by means of a Thin Metal Plate... with a purpose-designed ability to either to become warped into a slightly Conical Shape when the TC moves towards in the motor along the transmission shaft ...or it becomes a slightly Concave Shape as the TC moves backwards towards the Transmission along the same axis of the Transmission Shaft.

Upon reflection... having the engine bouncing and rolling about so erratically up and down and left and right upon three imperfect Shock Mounts during moments of Hard Acceleration and Hard Braking as well would certainly cause those dynamics to become shifted around and interfere with what would otherwise be a more controlled forward and backwards motions with no other forces being induced along the way if the Motor Mounts were in GOOD condition.

So taken all in all... the idea of having Bad Motor Mounts as a cause for Flex-Plate Failure seems to make an awful lot of sense. I cannot think of another reason why the company making the Flex-Plates would have stressed being aware of this situation unless they had a damned good experiential reason for doing so.
 
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mrrsm

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With the possible connection of the Bad Mounts-To-Cracking-Flex-Plate issues being suggested here... Should you begin to hear the Symptomatic, Rhythmic "Ticking-Clicking-Clanking" associated with Cracks and Fractures in your Flex-Plate... Safely elevate and support your SUV and get underneath the Engine to look up under the areas for the Motor Mounts for some Black-Sticky-Dirty-Oil residue along the Motor Mount Struts and upon the curvature of the adjacent Body Well Panel areas for any Sticky Residue that looks like Old Oil leaked out or sprayed around there... but with no possible sources coming from the engine components or covers that could cause such a leak around those areas. The intermediate Rubber Shock Mount Bulbs may show signs of cracking and leaking in plain view as well.

When Brand New, the Motor Mounts have a thick, viscous "Jellied-Center" (not much different than a Jelly donut) that is well designed as a Shock Absorbing material... but once emptied out of those bulbous Rubber Containers... the Motor Mounts will collapse and become less than useless things for the absorption of Motion and Shocks.

And... as improbable as this seems to be... when your start imagining that your Flex-Plate is the problem with noises coming from under the Engine and Transmission... Motor Mounts should come to mind as a possible cause for its failure, If the sounds emanating down there also have a bright, ringing tone to them... before deciding that the problem is definitely with the Flex-Plate... Shut off the Engine and use a Dead Blow Hammer to tap around under the CAT Can... and listen for a rebound of any loose pieces of Broken Cat Converter Ceramic Honeycombs that can make such metallic sounds. Otherwise ...isolating exactly what is causing such noises can be very difficult while under or near those areas of the Engine/Transmission and adjacent spaces with the engine idling.

Unless you can say for certain that they are in perfect order... keep in mind that unless you purchase a pair of AC-Delco Motor Mounts well ahead and have them tucked away on the shelf somewhere for just such an event... they might be very hard to find. They are a lot more expensive than the Off Brand... around $150.00 per pair... but they ordinarily will last a good deal longer than the Non-OEM flavors also touted on-line. Here is look at the ones you will want:

http://photobucket.com/gallery/user...1BVExBU0VOR0lORVNXQVAvRFNDMDY3MDEuanBn/?ref=1

... and while you are at it, if you are still searching for the right one to order ... as of 12-01-2017... the Price on the GM 4.2L OEM Factory Flex-Plate has dropped by $30.00 to around $60.00 at this GM Parts Site:

https://www.gmpartscenter.net/oem-parts/gm-plate-a-trns-flex-12576272
 
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