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Discussion Starter #1
Hey guys, I'm young and stupid and need to figure out what's going on with my car's transmission before my wife kills me.

I have a 66 I6 coupe with the 3 speed auto and it's my daily driver to-from work. I have a few problems, but we'll focus on the big one:

The transmission has some sort of a knock/rattle. To describe it more clearly, imagine putting a baseball card in the spokes of a bike... except the baseball card and spokes are both made of steel and are going VERY fast. It happens for a few seconds when I start up the car and then calms down until I get on the highway. At speeds greater than 60 mph, whenever I unload the drivetrain (quickly take my foot off the gas or drive down-hill), I get a rattle as if there's some sort of metal disk in my tranny and it's going to explode and fly out. If I get it going really fast (75-80) and let off the gas I fear for my own life (it sounds like a machine gun), but if I'm slower (anywhere below 35) it doesn't happen at all unless I put it into park or neutral.

So the engineer in me tells me that the variables in this equation are engine rpm, speed, and torque... but I don't know enough to reach a conclusion beyond that.

Important note: my transmission is leaking in about 7,000 places and I constantly have to refill the ATF (but the noise is still there, albeit less severe, when the ATF is full).

What the hell is going on in there?! and what are my options?

Thanks for you help,

Joe in Mississippi
 

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The easiest candidate to look at are the bolts that hold the flex plate to the torque converter. You can accesst them through the removable plate at the front of the trans. Should be torqued and I would locktight them also. Ask me how I know this might be the problem.
 

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The easiest candidate to look at are the bolts that hold the flex plate to the torque converter. You can accesst them through the removable plate at the front of the trans. Should be torqued and I would locktight them also. Ask me how I know this might be the problem.

2 questions:

1) is that a P-51 in your picture?

2) Although I have never heard of a torque converter or flex plate, I'm sure I can figure that out... but do I need any special tools or a lift to tighten them?

Thanks again for you help,
Joe
 

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The 64-70 I6 with C4 has a flex plate. These were known for cracking. Pull the inspection cover and examine the flex plate.

If that's it, you're looking at about $30. Plus installation.

There's only a few places a C4 can leak.

O-ring on filler tube.
Oil pan.
O-ring and seal on shift selector.
Slip yoke seal.
Torque converter input seal.
 

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Any other Ideas.

I know this is an old post but I'm having the exact same problem. I checked the bolts they were very tight would not move. Not sure where else to go from here. Would like to take it somewhere to get checked out but not sure if it should go to engine shop or transmission shop.

Thanks,

Joe
 

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Checked everything.

Yes I checked the Flexplate no cracks. The bolts are tight and there doesnt seem to be anything rubbing. Also all the teeth look fine on the converter. Dont know where else to go from here. It runs fine shifts thru all grears fine. Just does the rettle thing when it sits for a while at first start up and when it goes above 60mpg or when i give it full throttle in park.

Thanks,

Joe
 

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Any other ideas on this before I take it to the shop. I got an answer from the OP and he said this.

That was a while ago and I've since sold the car, but I'm pretty sure the bolts connecting my transmission to my torque converter...

Thanks,
Joe
 
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