[AMC-List] Re; 258 engine balance and flexplate

[farna@xxxxxxx]

The only situation I can think of where the flexplate could damage the trans is if the center breaks completely out. That could let the converter slip back and forth and partially disengage from the hub or "sling" out of alignment and damage the pump and front seal. 

I had that happen once on my 63 American (196, M-35). Luckily it broke loose just as I was starting to take off (just over idle speed) and the BW converter has a pilot shaft to keep it aligned. Makes a lot of noise when that happens, and barely moves even if the engine is revved up. I got it out of the road under it's own power, that was as far as I went. 

The flexplate cracked (broke) around the reinforcing ring and had radial cracks. No indication of anything wrong at all until it broke loose. I replaced the torque converter because there was a crack partially around the pilot shaft, don't know if that's from when it broke loose (most likely) or when I revved the engine to move the car. I replaced it with a slightly thicker flexplate made in the aircraft shop from high grade stainless. No other damage, even the seal looked good, but I replace the front seal in an auto trans ANY time the trans comes out if it's been in there more than a few weeks. $10 seal, lots of work to drop the trans...

The 196 flexplate is just a 16-18 gauge hardened steel flat disc 10" or so (don't have exact measurement) in diameter, the starter ring gear is on the converter. Easy to make one -- I tack welded the center back in the broke one and used it to locate the bolt holes. If it hadn't been hardened steel I don't think it would have broke. A piece of 16 gauge cold rolled steel works fine as a substitute. I suggest closely inspecting any 196 flexplate when the trans is out, and even if it's original and looks good I'd replace it. Andre Jacobs (akjamc@xxxxxxxx) makes replacements. I think he doubles 18 gauge steel (you just bolt the two together on the crank).  

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On Fri, 15 Dec 2006, John Elle wrote:

> The only verified bad flex plate I ever had on an automobile
> I purchased the car with it and sold it many years later
> with the flex plate still in it. It had radial cracks running
> out from the center hub.  Of course it was a Cheby.

Tom Jennings replied:
The flexplate on the '73 Hornet I took the motor out had the
same type cracks; it probably made a noise but it fit together
like gear teeth so I don't think it mattered to the P.O.; it
couldn't walk around because the crack was under the bolt heads.

Even that wouldn't hurt the transmission!

--
Frank Swygert
Publisher, "American Motors Cars" 
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