Turbo 350C problems or Flexplate?

[Matt Man]

When I was moving up to Idaho back in August, I got to Wells Nevada and while I was at my one of many fuel stops for the day I heard a faint knocking sound at idle but went away with any kind of rpm. I finally got to my new home in Idaho and did some investigating and the knocking sound only comes after driving it on the freeway and only while it is in gear. If I drive it around town there is no knocking sound. Now fast forward to the last few weeks and there is a big shudder when the converter locks up and now I can hear a grinding/vibration sound when driving around. The noise happens when it reaches a certain revolution like room room room if that makes any sense lol. I unplugged the electrical connection on the side of the trans for the lockup and there is no shudder but there is still a grinding and vibration like I mentioned before. The trans was rebuilt earlier this year with a new lockup converter. The transmission shifts fine and the fluid looks nice bright red and clean no shavings etc. I know new parts can fail but I am at a loss here any ideas? Flexplate maybe?

Also, this might be unrelated but my starter has been turning over really slow sometimes and today when I was out it BARELY started the truck. So my question is could the flex plate be warped or cracked causing the starter to drag more and ultimately making all this noise. Other times it starts really quick like it normally does. Any advice would be appreciated.

EDIT: I did pull the inspection cover and made sure the 3 bolts holding the converter to the flexplate were tight also I checked the bell housing bolts no issues there.

[SunSoaked]

Did you put an aggresive shift kit in it when it was rebuilt? I had a 700 that was rebuilt with a hard kit in it. It cracked the flexplate a few months later. The noise was only noticable during idle after it was warmed up. And, the cracks were not visible until the trans came out.
How you liking your new Idaho location? I'm a ID native near you (Burley) trying despertly to get back. I've had enough of the desert and 120* Summers!

[Matt Man]

Originally Posted by SunSoaked

Did you put an aggresive shift kit in it when it was rebuilt? I had a 700 that was rebuilt with a hard kit in it. It cracked the flexplate a few months later. The noise was only noticable during idle after it was warmed up. And, the cracks were not visible until the trans came out.
How you liking your new Idaho location? I'm a ID native near you (Burley) trying despertly to get back. I've had enough of the desert and 120* Summers!

Sorry for the late reply, but Idaho is great the weather is a lot cooler from where I came from (San Bernardino) way less traffic etc. Overall, I am really happy here so far.