I pulled the engine out of my 2nd truck, 1968 F100 2wd 360 C6. I found the flex plate was cracked and broken off where it bolts to the crank. It was completely disconnected from the crank. It had signs of wear at the crack.

The engine made a hollow knocking sound at idle that went away just above idle and the tranny sometimes made a high-pitched screaching sound when backing up.

Could this have been the problem?

Could I have cracked this by not having the TC set back far enough during engine installation? It has less than 1000 miles and good compression and power, just made a bunch of noise.

 

Your transmission was out of alignment with the engine. Did you draw them together with the bolts?

 

It was over 10 years ago and I'd never done an auto trans before, so I probably screwed things up. I didn't know how to set the TC back in and probably didn't have it set right. The funny thing is that it ran great, just made the noise.

By the way, how do you know if the TC is set back in properly?

 

When you put the TC back into the tranny the notches line up with the pump drive (get down and take a look inside). If everything is lined up it will slide back in the tranny like it belonged there. DON'T force it! I have seen several examples of what happens when that is done. Make sure the mounting surfaces are clean with no burrs etc. Check any locating pins the application uses. When you bring the tranny back up to mate with the engine you almost need a tranny jack. You can use a small dolly and three screw jacks in a pinch. When the tranny is about 1-2" away reach in and turn the converter to align with the holes in the flexplate. The transmission can then be moved forwards into contact with the block. raise the jacks as required to keep everything aligned (this is where a real tranny jack shines. If it does not mate easily with a solid "thunk" there is a problem. Back it out and check, something isn't lining up. Never use the bolts to force the parts together. The bolts should thread in with your fingers. Rotate the engine by hand to bring all of the converter bolts into view.

You can buy transmission jack adaptors at Harbor Freight or Northern Hydraulics. You can also rent them...